Freescale u-boot repository
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Wolfgang Denk b8aa57b5d4 tools/setlocalversion: use a git-describe-ish format 13 years ago
api Fix remaining CONFIG_COMMANDS 13 years ago
api_examples API: Provide dummy halt() in the glue layer. 13 years ago
board HMI1001: add support for MPC5200 Rev. B processors. 13 years ago
common common/kgdb.c: fix 'dereferencing type-punned pointer' warning 13 years ago
cpu PPC4xx (Sequoia): Fix Ethernet "remote fault" problems 13 years ago
disk Build: split COBJS value into multiple lines 13 years ago
doc 8610HPCD: Document the flashbank selection switches. 13 years ago
drivers net: rtl8169: Add processing when OWNbit did't enable in rtl_recv() 13 years ago
examples examples/Makefile: build "hello_world" on 8xx, too. 13 years ago
fs Fix checking fat32 cluster size. 13 years ago
include Merge branch 'master' of git://www.denx.de/git/u-boot-mpc83xx 13 years ago
lib_arm Merge branch '080208_dupint' of git://linux-arm.org/u-boot-armdev 13 years ago
lib_avr32 AVR32: Initialize ipaddr, loadaddr and bootfile at startup 13 years ago
lib_blackfin punt Blackfin VDSP headers and import sanitized/auto-generated ones 13 years ago
lib_generic Fix 64-bit vsprintf. 13 years ago
lib_i386 disk/ doc/ lib_*/ and tools/: Remove lingering references to CFG_CMD_* symbols. 14 years ago
lib_m68k ColdFire: Add MCF5227x cpu and M52277EVB support-1 13 years ago
lib_microblaze [PATCH] Add support for design without interrupt controller 13 years ago
lib_mips MIPS: Fix CFG_NO_FLASH support 13 years ago
lib_nios Move "ar" flags to config.mk to allow for silent "make -s" 14 years ago
lib_nios2 Move "ar" flags to config.mk to allow for silent "make -s" 14 years ago
lib_ppc lwmon5: enable hardware watchdog 13 years ago
lib_sh Fix coding style issues; update CHANGELOG. 13 years ago
libfdt LIBFDT: use memmove() instead of memcpy() 13 years ago
nand_spl Fix linker scripts: add NOLOAD atribute to .bss/.sbss sections 13 years ago
net net: Print error message upon net usage when no ethernet-interface is found 13 years ago
onenand_ipl Coding style cleanup; update CHANGELOG. 13 years ago
post Fix warnings while compilation of post/drivers/memory.c 13 years ago
tools tools/setlocalversion: use a git-describe-ish format 13 years ago
.gitignore Merge branch 'master' of git://www.denx.de/git/u-boot-blackfin 13 years ago
CHANGELOG Release v1.3.2 13 years ago
CHANGELOG-before-U-Boot-1.1.5 Fix an ancient CHANGELOG conflict 14 years ago
COPYING Allow use of include/image.h and include/asm-*/u-boot.h in proprietary code. 15 years ago
CREDITS Coding style cleanup. Prepare v1.3.2-rc2 release candidate 13 years ago
MAINTAINERS IDS8247: update MAINTAINER entry. 13 years ago
MAKEALL Merge branch '080131_artila' of git://linux-arm.org/u-boot-armdev 13 years ago
Makefile Makefile: make build silently again. 13 years ago
README Merge branch 'master' of git://www.denx.de/git/u-boot-blackfin 13 years ago
arm_config.mk Initial revision 19 years ago
avr32_config.mk AVR32: Build position-independent u-boot 14 years ago
blackfin_config.mk generate u-boot.ldr for Blackfin targets 13 years ago
config.mk include autoconf.mk before any other .mk files 13 years ago
i386_config.mk * Patch by Daniel Engstrm, 13 Nov 2002: 18 years ago
m68k_config.mk * Patch by Bernhard Kuhn, 28 Nov 2003: 17 years ago
microblaze_config.mk [Microblaze][PATCH] part 2 14 years ago
mips_config.mk [MIPS] Add PIC-related switches to PLATFORM_{CPP,LD}FLAGS and cleanup 13 years ago
mkconfig Add support for a saving build objects in a separate directory. 14 years ago
nios2_config.mk Nios II - Fix I/O Macros and mini-app stubs 15 years ago
nios_config.mk Patch by Scott McNutt, 25 Apr 2004: 17 years ago
ppc_config.mk * Vince Husovsky, 7 Nov 2002: 18 years ago
rules.mk Add support for a saving build objects in a separate directory. 14 years ago
sh_config.mk sh: Update core code of SuperH. 13 years ago

README

#
# (C) Copyright 2000 - 2005
# Wolfgang Denk, DENX Software Engineering, wd@denx.de.
#
# See file CREDITS for list of people who contributed to this
# project.
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as
# published by the Free Software Foundation; either version 2 of
# the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston,
# MA 02111-1307 USA
#

Summary:
========

This directory contains the source code for U-Boot, a boot loader for
Embedded boards based on PowerPC, ARM, MIPS and several other
processors, which can be installed in a boot ROM and used to
initialize and test the hardware or to download and run application
code.

The development of U-Boot is closely related to Linux: some parts of
the source code originate in the Linux source tree, we have some
header files in common, and special provision has been made to
support booting of Linux images.

Some attention has been paid to make this software easily
configurable and extendable. For instance, all monitor commands are
implemented with the same call interface, so that it's very easy to
add new commands. Also, instead of permanently adding rarely used
code (for instance hardware test utilities) to the monitor, you can
load and run it dynamically.


Status:
=======

In general, all boards for which a configuration option exists in the
Makefile have been tested to some extent and can be considered
"working". In fact, many of them are used in production systems.

In case of problems see the CHANGELOG and CREDITS files to find out
who contributed the specific port.


Where to get help:
==================

In case you have questions about, problems with or contributions for
U-Boot you should send a message to the U-Boot mailing list at
<u-boot-users@lists.sourceforge.net>. There is also an archive of
previous traffic on the mailing list - please search the archive
before asking FAQ's. Please see
http://lists.sourceforge.net/lists/listinfo/u-boot-users/


Where we come from:
===================

- start from 8xxrom sources
- create PPCBoot project (http://sourceforge.net/projects/ppcboot)
- clean up code
- make it easier to add custom boards
- make it possible to add other [PowerPC] CPUs
- extend functions, especially:
* Provide extended interface to Linux boot loader
* S-Record download
* network boot
* PCMCIA / CompactFLash / ATA disk / SCSI ... boot
- create ARMBoot project (http://sourceforge.net/projects/armboot)
- add other CPU families (starting with ARM)
- create U-Boot project (http://sourceforge.net/projects/u-boot)


Names and Spelling:
===================

The "official" name of this project is "Das U-Boot". The spelling
"U-Boot" shall be used in all written text (documentation, comments
in source files etc.). Example:

This is the README file for the U-Boot project.

File names etc. shall be based on the string "u-boot". Examples:

include/asm-ppc/u-boot.h

#include <asm/u-boot.h>

Variable names, preprocessor constants etc. shall be either based on
the string "u_boot" or on "U_BOOT". Example:

U_BOOT_VERSION u_boot_logo
IH_OS_U_BOOT u_boot_hush_start


Versioning:
===========

U-Boot uses a 3 level version number containing a version, a
sub-version, and a patchlevel: "U-Boot-2.34.5" means version "2",
sub-version "34", and patchlevel "4".

The patchlevel is used to indicate certain stages of development
between released versions, i. e. officially released versions of
U-Boot will always have a patchlevel of "0".


Directory Hierarchy:
====================

- board Board dependent files
- common Misc architecture independent functions
- cpu CPU specific files
- 74xx_7xx Files specific to Freescale MPC74xx and 7xx CPUs
- arm720t Files specific to ARM 720 CPUs
- arm920t Files specific to ARM 920 CPUs
- at91rm9200 Files specific to Atmel AT91RM9200 CPU
- imx Files specific to Freescale MC9328 i.MX CPUs
- s3c24x0 Files specific to Samsung S3C24X0 CPUs
- arm925t Files specific to ARM 925 CPUs
- arm926ejs Files specific to ARM 926 CPUs
- arm1136 Files specific to ARM 1136 CPUs
- at32ap Files specific to Atmel AVR32 AP CPUs
- i386 Files specific to i386 CPUs
- ixp Files specific to Intel XScale IXP CPUs
- mcf52x2 Files specific to Freescale ColdFire MCF52x2 CPUs
- mcf5227x Files specific to Freescale ColdFire MCF5227x CPUs
- mcf532x Files specific to Freescale ColdFire MCF5329 CPUs
- mcf5445x Files specific to Freescale ColdFire MCF5445x CPUs
- mcf547x_8x Files specific to Freescale ColdFire MCF547x_8x CPUs
- mips Files specific to MIPS CPUs
- mpc5xx Files specific to Freescale MPC5xx CPUs
- mpc5xxx Files specific to Freescale MPC5xxx CPUs
- mpc8xx Files specific to Freescale MPC8xx CPUs
- mpc8220 Files specific to Freescale MPC8220 CPUs
- mpc824x Files specific to Freescale MPC824x CPUs
- mpc8260 Files specific to Freescale MPC8260 CPUs
- mpc85xx Files specific to Freescale MPC85xx CPUs
- nios Files specific to Altera NIOS CPUs
- nios2 Files specific to Altera Nios-II CPUs
- ppc4xx Files specific to AMCC PowerPC 4xx CPUs
- pxa Files specific to Intel XScale PXA CPUs
- s3c44b0 Files specific to Samsung S3C44B0 CPUs
- sa1100 Files specific to Intel StrongARM SA1100 CPUs
- disk Code for disk drive partition handling
- doc Documentation (don't expect too much)
- drivers Commonly used device drivers
- dtt Digital Thermometer and Thermostat drivers
- examples Example code for standalone applications, etc.
- include Header Files
- lib_arm Files generic to ARM architecture
- lib_avr32 Files generic to AVR32 architecture
- lib_generic Files generic to all architectures
- lib_i386 Files generic to i386 architecture
- lib_m68k Files generic to m68k architecture
- lib_mips Files generic to MIPS architecture
- lib_nios Files generic to NIOS architecture
- lib_ppc Files generic to PowerPC architecture
- libfdt Library files to support flattened device trees
- net Networking code
- post Power On Self Test
- rtc Real Time Clock drivers
- tools Tools to build S-Record or U-Boot images, etc.

Software Configuration:
=======================

Configuration is usually done using C preprocessor defines; the
rationale behind that is to avoid dead code whenever possible.

There are two classes of configuration variables:

* Configuration _OPTIONS_:
These are selectable by the user and have names beginning with
"CONFIG_".

* Configuration _SETTINGS_:
These depend on the hardware etc. and should not be meddled with if
you don't know what you're doing; they have names beginning with
"CFG_".

Later we will add a configuration tool - probably similar to or even
identical to what's used for the Linux kernel. Right now, we have to
do the configuration by hand, which means creating some symbolic
links and editing some configuration files. We use the TQM8xxL boards
as an example here.


Selection of Processor Architecture and Board Type:
---------------------------------------------------

For all supported boards there are ready-to-use default
configurations available; just type "make <board_name>_config".

Example: For a TQM823L module type:

cd u-boot
make TQM823L_config

For the Cogent platform, you need to specify the cpu type as well;
e.g. "make cogent_mpc8xx_config". And also configure the cogent
directory according to the instructions in cogent/README.


Configuration Options:
----------------------

Configuration depends on the combination of board and CPU type; all
such information is kept in a configuration file
"include/configs/<board_name>.h".

Example: For a TQM823L module, all configuration settings are in
"include/configs/TQM823L.h".


Many of the options are named exactly as the corresponding Linux
kernel configuration options. The intention is to make it easier to
build a config tool - later.


The following options need to be configured:

- CPU Type: Define exactly one, e.g. CONFIG_MPC85XX.

- Board Type: Define exactly one, e.g. CONFIG_MPC8540ADS.

- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
Define exactly one, e.g. CONFIG_ATSTK1002

- CPU Module Type: (if CONFIG_COGENT is defined)
Define exactly one of
CONFIG_CMA286_60_OLD
--- FIXME --- not tested yet:
CONFIG_CMA286_60, CONFIG_CMA286_21, CONFIG_CMA286_60P,
CONFIG_CMA287_23, CONFIG_CMA287_50

- Motherboard Type: (if CONFIG_COGENT is defined)
Define exactly one of
CONFIG_CMA101, CONFIG_CMA102

- Motherboard I/O Modules: (if CONFIG_COGENT is defined)
Define one or more of
CONFIG_CMA302

- Motherboard Options: (if CONFIG_CMA101 or CONFIG_CMA102 are defined)
Define one or more of
CONFIG_LCD_HEARTBEAT - update a character position on
the lcd display every second with
a "rotator" |\-/|\-/

- Board flavour: (if CONFIG_MPC8260ADS is defined)
CONFIG_ADSTYPE
Possible values are:
CFG_8260ADS - original MPC8260ADS
CFG_8266ADS - MPC8266ADS
CFG_PQ2FADS - PQ2FADS-ZU or PQ2FADS-VR
CFG_8272ADS - MPC8272ADS

- MPC824X Family Member (if CONFIG_MPC824X is defined)
Define exactly one of
CONFIG_MPC8240, CONFIG_MPC8245

- 8xx CPU Options: (if using an MPC8xx cpu)
CONFIG_8xx_GCLK_FREQ - deprecated: CPU clock if
get_gclk_freq() cannot work
e.g. if there is no 32KHz
reference PIT/RTC clock
CONFIG_8xx_OSCLK - PLL input clock (either EXTCLK
or XTAL/EXTAL)

- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
CFG_8xx_CPUCLK_MIN
CFG_8xx_CPUCLK_MAX
CONFIG_8xx_CPUCLK_DEFAULT
See doc/README.MPC866

CFG_MEASURE_CPUCLK

Define this to measure the actual CPU clock instead
of relying on the correctness of the configured
values. Mostly useful for board bringup to make sure
the PLL is locked at the intended frequency. Note
that this requires a (stable) reference clock (32 kHz
RTC clock or CFG_8XX_XIN)

- Intel Monahans options:
CFG_MONAHANS_RUN_MODE_OSC_RATIO

Defines the Monahans run mode to oscillator
ratio. Valid values are 8, 16, 24, 31. The core
frequency is this value multiplied by 13 MHz.

CFG_MONAHANS_TURBO_RUN_MODE_RATIO

Defines the Monahans turbo mode to oscillator
ratio. Valid values are 1 (default if undefined) and
2. The core frequency as calculated above is multiplied
by this value.

- Linux Kernel Interface:
CONFIG_CLOCKS_IN_MHZ

U-Boot stores all clock information in Hz
internally. For binary compatibility with older Linux
kernels (which expect the clocks passed in the
bd_info data to be in MHz) the environment variable
"clocks_in_mhz" can be defined so that U-Boot
converts clock data to MHZ before passing it to the
Linux kernel.
When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
"clocks_in_mhz=1" is automatically included in the
default environment.

CONFIG_MEMSIZE_IN_BYTES [relevant for MIPS only]

When transfering memsize parameter to linux, some versions
expect it to be in bytes, others in MB.
Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.

CONFIG_OF_LIBFDT / CONFIG_OF_FLAT_TREE

New kernel versions are expecting firmware settings to be
passed using flattened device trees (based on open firmware
concepts).

CONFIG_OF_LIBFDT
* New libfdt-based support
* Adds the "fdt" command
* The bootm command automatically updates the fdt

CONFIG_OF_FLAT_TREE
* Deprecated, see CONFIG_OF_LIBFDT
* Original ft_build.c-based support
* Automatically modifies the dft as part of the bootm command
* The environment variable "disable_of", when set,
disables this functionality.

OF_CPU - The proper name of the cpus node.
OF_SOC - The proper name of the soc node.
OF_TBCLK - The timebase frequency.
OF_STDOUT_PATH - The path to the console device

boards with QUICC Engines require OF_QE to set UCC mac addresses

CONFIG_OF_HAS_BD_T

* CONFIG_OF_LIBFDT - enables the "fdt bd_t" command
* CONFIG_OF_FLAT_TREE - The resulting flat device tree
will have a copy of the bd_t. Space should be
pre-allocated in the dts for the bd_t.

CONFIG_OF_HAS_UBOOT_ENV

* CONFIG_OF_LIBFDT - enables the "fdt env" command
* CONFIG_OF_FLAT_TREE - The resulting flat device tree
will have a copy of u-boot's environment variables

CONFIG_OF_BOARD_SETUP

Board code has addition modification that it wants to make
to the flat device tree before handing it off to the kernel

CONFIG_OF_BOOT_CPU

This define fills in the correct boot cpu in the boot
param header, the default value is zero if undefined.

- Serial Ports:
CFG_PL010_SERIAL

Define this if you want support for Amba PrimeCell PL010 UARTs.

CFG_PL011_SERIAL

Define this if you want support for Amba PrimeCell PL011 UARTs.

CONFIG_PL011_CLOCK

If you have Amba PrimeCell PL011 UARTs, set this variable to
the clock speed of the UARTs.

CONFIG_PL01x_PORTS

If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
define this to a list of base addresses for each (supported)
port. See e.g. include/configs/versatile.h


- Console Interface:
Depending on board, define exactly one serial port
(like CONFIG_8xx_CONS_SMC1, CONFIG_8xx_CONS_SMC2,
CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
console by defining CONFIG_8xx_CONS_NONE

Note: if CONFIG_8xx_CONS_NONE is defined, the serial
port routines must be defined elsewhere
(i.e. serial_init(), serial_getc(), ...)

CONFIG_CFB_CONSOLE
Enables console device for a color framebuffer. Needs following
defines (cf. smiLynxEM, i8042, board/eltec/bab7xx)
VIDEO_FB_LITTLE_ENDIAN graphic memory organisation
(default big endian)
VIDEO_HW_RECTFILL graphic chip supports
rectangle fill
(cf. smiLynxEM)
VIDEO_HW_BITBLT graphic chip supports
bit-blit (cf. smiLynxEM)
VIDEO_VISIBLE_COLS visible pixel columns
(cols=pitch)
VIDEO_VISIBLE_ROWS visible pixel rows
VIDEO_PIXEL_SIZE bytes per pixel
VIDEO_DATA_FORMAT graphic data format
(0-5, cf. cfb_console.c)
VIDEO_FB_ADRS framebuffer address
VIDEO_KBD_INIT_FCT keyboard int fct
(i.e. i8042_kbd_init())
VIDEO_TSTC_FCT test char fct
(i.e. i8042_tstc)
VIDEO_GETC_FCT get char fct
(i.e. i8042_getc)
CONFIG_CONSOLE_CURSOR cursor drawing on/off
(requires blink timer
cf. i8042.c)
CFG_CONSOLE_BLINK_COUNT blink interval (cf. i8042.c)
CONFIG_CONSOLE_TIME display time/date info in
upper right corner
(requires CONFIG_CMD_DATE)
CONFIG_VIDEO_LOGO display Linux logo in
upper left corner
CONFIG_VIDEO_BMP_LOGO use bmp_logo.h instead of
linux_logo.h for logo.
Requires CONFIG_VIDEO_LOGO
CONFIG_CONSOLE_EXTRA_INFO
addional board info beside
the logo

When CONFIG_CFB_CONSOLE is defined, video console is
default i/o. Serial console can be forced with
environment 'console=serial'.

When CONFIG_SILENT_CONSOLE is defined, all console
messages (by U-Boot and Linux!) can be silenced with
the "silent" environment variable. See
doc/README.silent for more information.

- Console Baudrate:
CONFIG_BAUDRATE - in bps
Select one of the baudrates listed in
CFG_BAUDRATE_TABLE, see below.
CFG_BRGCLK_PRESCALE, baudrate prescale

- Interrupt driven serial port input:
CONFIG_SERIAL_SOFTWARE_FIFO

PPC405GP only.
Use an interrupt handler for receiving data on the
serial port. It also enables using hardware handshake
(RTS/CTS) and UART's built-in FIFO. Set the number of
bytes the interrupt driven input buffer should have.

Leave undefined to disable this feature, including
disable the buffer and hardware handshake.

- Console UART Number:
CONFIG_UART1_CONSOLE

AMCC PPC4xx only.
If defined internal UART1 (and not UART0) is used
as default U-Boot console.

- Boot Delay: CONFIG_BOOTDELAY - in seconds
Delay before automatically booting the default image;
set to -1 to disable autoboot.

See doc/README.autoboot for these options that
work with CONFIG_BOOTDELAY. None are required.
CONFIG_BOOT_RETRY_TIME
CONFIG_BOOT_RETRY_MIN
CONFIG_AUTOBOOT_KEYED
CONFIG_AUTOBOOT_PROMPT
CONFIG_AUTOBOOT_DELAY_STR
CONFIG_AUTOBOOT_STOP_STR
CONFIG_AUTOBOOT_DELAY_STR2
CONFIG_AUTOBOOT_STOP_STR2
CONFIG_ZERO_BOOTDELAY_CHECK
CONFIG_RESET_TO_RETRY

- Autoboot Command:
CONFIG_BOOTCOMMAND
Only needed when CONFIG_BOOTDELAY is enabled;
define a command string that is automatically executed
when no character is read on the console interface
within "Boot Delay" after reset.

CONFIG_BOOTARGS
This can be used to pass arguments to the bootm
command. The value of CONFIG_BOOTARGS goes into the
environment value "bootargs".

CONFIG_RAMBOOT and CONFIG_NFSBOOT
The value of these goes into the environment as
"ramboot" and "nfsboot" respectively, and can be used
as a convenience, when switching between booting from
ram and nfs.

- Pre-Boot Commands:
CONFIG_PREBOOT

When this option is #defined, the existence of the
environment variable "preboot" will be checked
immediately before starting the CONFIG_BOOTDELAY
countdown and/or running the auto-boot command resp.
entering interactive mode.

This feature is especially useful when "preboot" is
automatically generated or modified. For an example
see the LWMON board specific code: here "preboot" is
modified when the user holds down a certain
combination of keys on the (special) keyboard when
booting the systems

- Serial Download Echo Mode:
CONFIG_LOADS_ECHO
If defined to 1, all characters received during a
serial download (using the "loads" command) are
echoed back. This might be needed by some terminal
emulations (like "cu"), but may as well just take
time on others. This setting #define's the initial
value of the "loads_echo" environment variable.

- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
CONFIG_KGDB_BAUDRATE
Select one of the baudrates listed in
CFG_BAUDRATE_TABLE, see below.

- Monitor Functions:
Monitor commands can be included or excluded
from the build by using the #include files
"config_cmd_all.h" and #undef'ing unwanted
commands, or using "config_cmd_default.h"
and augmenting with additional #define's
for wanted commands.

The default command configuration includes all commands
except those marked below with a "*".

CONFIG_CMD_ASKENV * ask for env variable
CONFIG_CMD_AUTOSCRIPT Autoscript Support
CONFIG_CMD_BDI bdinfo
CONFIG_CMD_BEDBUG * Include BedBug Debugger
CONFIG_CMD_BMP * BMP support
CONFIG_CMD_BSP * Board specific commands
CONFIG_CMD_BOOTD bootd
CONFIG_CMD_CACHE * icache, dcache
CONFIG_CMD_CONSOLE coninfo
CONFIG_CMD_DATE * support for RTC, date/time...
CONFIG_CMD_DHCP * DHCP support
CONFIG_CMD_DIAG * Diagnostics
CONFIG_CMD_DOC * Disk-On-Chip Support
CONFIG_CMD_DTT * Digital Therm and Thermostat
CONFIG_CMD_ECHO echo arguments
CONFIG_CMD_EEPROM * EEPROM read/write support
CONFIG_CMD_ELF * bootelf, bootvx
CONFIG_CMD_ENV saveenv
CONFIG_CMD_FDC * Floppy Disk Support
CONFIG_CMD_FAT * FAT partition support
CONFIG_CMD_FDOS * Dos diskette Support
CONFIG_CMD_FLASH flinfo, erase, protect
CONFIG_CMD_FPGA FPGA device initialization support
CONFIG_CMD_HWFLOW * RTS/CTS hw flow control
CONFIG_CMD_I2C * I2C serial bus support
CONFIG_CMD_IDE * IDE harddisk support
CONFIG_CMD_IMI iminfo
CONFIG_CMD_IMLS List all found images
CONFIG_CMD_IMMAP * IMMR dump support
CONFIG_CMD_IRQ * irqinfo
CONFIG_CMD_ITEST Integer/string test of 2 values
CONFIG_CMD_JFFS2 * JFFS2 Support
CONFIG_CMD_KGDB * kgdb
CONFIG_CMD_LOADB loadb
CONFIG_CMD_LOADS loads
CONFIG_CMD_MEMORY md, mm, nm, mw, cp, cmp, crc, base,
loop, loopw, mtest
CONFIG_CMD_MISC Misc functions like sleep etc
CONFIG_CMD_MMC * MMC memory mapped support
CONFIG_CMD_MII * MII utility commands
CONFIG_CMD_NAND * NAND support
CONFIG_CMD_NET bootp, tftpboot, rarpboot
CONFIG_CMD_PCI * pciinfo
CONFIG_CMD_PCMCIA * PCMCIA support
CONFIG_CMD_PING * send ICMP ECHO_REQUEST to network
host
CONFIG_CMD_PORTIO * Port I/O
CONFIG_CMD_REGINFO * Register dump
CONFIG_CMD_RUN run command in env variable
CONFIG_CMD_SAVES * save S record dump
CONFIG_CMD_SCSI * SCSI Support
CONFIG_CMD_SDRAM * print SDRAM configuration information
(requires CONFIG_CMD_I2C)
CONFIG_CMD_SETGETDCR Support for DCR Register access
(4xx only)
CONFIG_CMD_SPI * SPI serial bus support
CONFIG_CMD_USB * USB support
CONFIG_CMD_VFD * VFD support (TRAB)
CONFIG_CMD_BSP * Board SPecific functions
CONFIG_CMD_CDP * Cisco Discover Protocol support
CONFIG_CMD_FSL * Microblaze FSL support


EXAMPLE: If you want all functions except of network
support you can write:

#include "config_cmd_all.h"
#undef CONFIG_CMD_NET

Other Commands:
fdt (flattened device tree) command: CONFIG_OF_LIBFDT

Note: Don't enable the "icache" and "dcache" commands
(configuration option CONFIG_CMD_CACHE) unless you know
what you (and your U-Boot users) are doing. Data
cache cannot be enabled on systems like the 8xx or
8260 (where accesses to the IMMR region must be
uncached), and it cannot be disabled on all other
systems where we (mis-) use the data cache to hold an
initial stack and some data.


XXX - this list needs to get updated!

- Watchdog:
CONFIG_WATCHDOG
If this variable is defined, it enables watchdog
support. There must be support in the platform specific
code for a watchdog. For the 8xx and 8260 CPUs, the
SIU Watchdog feature is enabled in the SYPCR
register.

- U-Boot Version:
CONFIG_VERSION_VARIABLE
If this variable is defined, an environment variable
named "ver" is created by U-Boot showing the U-Boot
version as printed by the "version" command.
This variable is readonly.

- Real-Time Clock:

When CONFIG_CMD_DATE is selected, the type of the RTC
has to be selected, too. Define exactly one of the
following options:

CONFIG_RTC_MPC8xx - use internal RTC of MPC8xx
CONFIG_RTC_PCF8563 - use Philips PCF8563 RTC
CONFIG_RTC_MC146818 - use MC146818 RTC
CONFIG_RTC_DS1307 - use Maxim, Inc. DS1307 RTC
CONFIG_RTC_DS1337 - use Maxim, Inc. DS1337 RTC
CONFIG_RTC_DS1338 - use Maxim, Inc. DS1338 RTC
CONFIG_RTC_DS164x - use Dallas DS164x RTC
CONFIG_RTC_MAX6900 - use Maxim, Inc. MAX6900 RTC

Note that if the RTC uses I2C, then the I2C interface
must also be configured. See I2C Support, below.

- Timestamp Support:

When CONFIG_TIMESTAMP is selected, the timestamp
(date and time) of an image is printed by image
commands like bootm or iminfo. This option is
automatically enabled when you select CONFIG_CMD_DATE .

- Partition Support:
CONFIG_MAC_PARTITION and/or CONFIG_DOS_PARTITION
and/or CONFIG_ISO_PARTITION

If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
CONFIG_CMD_SCSI) you must configure support for at least
one partition type as well.

- IDE Reset method:
CONFIG_IDE_RESET_ROUTINE - this is defined in several
board configurations files but used nowhere!

CONFIG_IDE_RESET - is this is defined, IDE Reset will
be performed by calling the function
ide_set_reset(int reset)
which has to be defined in a board specific file

- ATAPI Support:
CONFIG_ATAPI

Set this to enable ATAPI support.

- LBA48 Support
CONFIG_LBA48

Set this to enable support for disks larger than 137GB
Also look at CFG_64BIT_LBA ,CFG_64BIT_VSPRINTF and CFG_64BIT_STRTOUL
Whithout these , LBA48 support uses 32bit variables and will 'only'
support disks up to 2.1TB.

CFG_64BIT_LBA:
When enabled, makes the IDE subsystem use 64bit sector addresses.
Default is 32bit.

- SCSI Support:
At the moment only there is only support for the
SYM53C8XX SCSI controller; define
CONFIG_SCSI_SYM53C8XX to enable it.

CFG_SCSI_MAX_LUN [8], CFG_SCSI_MAX_SCSI_ID [7] and
CFG_SCSI_MAX_DEVICE [CFG_SCSI_MAX_SCSI_ID *
CFG_SCSI_MAX_LUN] can be adjusted to define the
maximum numbers of LUNs, SCSI ID's and target
devices.
CFG_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)

- NETWORK Support (PCI):
CONFIG_E1000
Support for Intel 8254x gigabit chips.

CONFIG_EEPRO100
Support for Intel 82557/82559/82559ER chips.
Optional CONFIG_EEPRO100_SROM_WRITE enables eeprom
write routine for first time initialisation.

CONFIG_TULIP
Support for Digital 2114x chips.
Optional CONFIG_TULIP_SELECT_MEDIA for board specific
modem chip initialisation (KS8761/QS6611).

CONFIG_NATSEMI
Support for National dp83815 chips.

CONFIG_NS8382X
Support for National dp8382[01] gigabit chips.

- NETWORK Support (other):

CONFIG_DRIVER_LAN91C96
Support for SMSC's LAN91C96 chips.

CONFIG_LAN91C96_BASE
Define this to hold the physical address
of the LAN91C96's I/O space

CONFIG_LAN91C96_USE_32_BIT
Define this to enable 32 bit addressing

CONFIG_DRIVER_SMC91111
Support for SMSC's LAN91C111 chip

CONFIG_SMC91111_BASE
Define this to hold the physical address
of the device (I/O space)

CONFIG_SMC_USE_32_BIT
Define this if data bus is 32 bits

CONFIG_SMC_USE_IOFUNCS
Define this to use i/o functions instead of macros
(some hardware wont work with macros)

- USB Support:
At the moment only the UHCI host controller is
supported (PIP405, MIP405, MPC5200); define
CONFIG_USB_UHCI to enable it.
define CONFIG_USB_KEYBOARD to enable the USB Keyboard
and define CONFIG_USB_STORAGE to enable the USB
storage devices.
Note:
Supported are USB Keyboards and USB Floppy drives
(TEAC FD-05PUB).
MPC5200 USB requires additional defines:
CONFIG_USB_CLOCK
for 528 MHz Clock: 0x0001bbbb
CONFIG_USB_CONFIG
for differential drivers: 0x00001000
for single ended drivers: 0x00005000
CFG_USB_EVENT_POLL
May be defined to allow interrupt polling
instead of using asynchronous interrupts

- USB Device:
Define the below if you wish to use the USB console.
Once firmware is rebuilt from a serial console issue the
command "setenv stdin usbtty; setenv stdout usbtty" and
attach your usb cable. The Unix command "dmesg" should print
it has found a new device. The environment variable usbtty
can be set to gserial or cdc_acm to enable your device to
appear to a USB host as a Linux gserial device or a
Common Device Class Abstract Control Model serial device.
If you select usbtty = gserial you should be able to enumerate
a Linux host by
# modprobe usbserial vendor=0xVendorID product=0xProductID
else if using cdc_acm, simply setting the environment
variable usbtty to be cdc_acm should suffice. The following
might be defined in YourBoardName.h

CONFIG_USB_DEVICE
Define this to build a UDC device

CONFIG_USB_TTY
Define this to have a tty type of device available to
talk to the UDC device

CFG_CONSOLE_IS_IN_ENV
Define this if you want stdin, stdout &/or stderr to
be set to usbtty.

mpc8xx:
CFG_USB_EXTC_CLK 0xBLAH
Derive USB clock from external clock "blah"
- CFG_USB_EXTC_CLK 0x02

CFG_USB_BRG_CLK 0xBLAH
Derive USB clock from brgclk
- CFG_USB_BRG_CLK 0x04

If you have a USB-IF assigned VendorID then you may wish to
define your own vendor specific values either in BoardName.h
or directly in usbd_vendor_info.h. If you don't define
CONFIG_USBD_MANUFACTURER, CONFIG_USBD_PRODUCT_NAME,
CONFIG_USBD_VENDORID and CONFIG_USBD_PRODUCTID, then U-Boot
should pretend to be a Linux device to it's target host.

CONFIG_USBD_MANUFACTURER
Define this string as the name of your company for
- CONFIG_USBD_MANUFACTURER "my company"

CONFIG_USBD_PRODUCT_NAME
Define this string as the name of your product
- CONFIG_USBD_PRODUCT_NAME "acme usb device"

CONFIG_USBD_VENDORID
Define this as your assigned Vendor ID from the USB
Implementors Forum. This *must* be a genuine Vendor ID
to avoid polluting the USB namespace.
- CONFIG_USBD_VENDORID 0xFFFF

CONFIG_USBD_PRODUCTID
Define this as the unique Product ID
for your device
- CONFIG_USBD_PRODUCTID 0xFFFF


- MMC Support:
The MMC controller on the Intel PXA is supported. To
enable this define CONFIG_MMC. The MMC can be
accessed from the boot prompt by mapping the device
to physical memory similar to flash. Command line is
enabled with CONFIG_CMD_MMC. The MMC driver also works with
the FAT fs. This is enabled with CONFIG_CMD_FAT.

- Journaling Flash filesystem support:
CONFIG_JFFS2_NAND, CONFIG_JFFS2_NAND_OFF, CONFIG_JFFS2_NAND_SIZE,
CONFIG_JFFS2_NAND_DEV
Define these for a default partition on a NAND device

CFG_JFFS2_FIRST_SECTOR,
CFG_JFFS2_FIRST_BANK, CFG_JFFS2_NUM_BANKS
Define these for a default partition on a NOR device

CFG_JFFS_CUSTOM_PART
Define this to create an own partition. You have to provide a
function struct part_info* jffs2_part_info(int part_num)

If you define only one JFFS2 partition you may also want to
#define CFG_JFFS_SINGLE_PART 1
to disable the command chpart. This is the default when you
have not defined a custom partition

- Keyboard Support:
CONFIG_ISA_KEYBOARD

Define this to enable standard (PC-Style) keyboard
support

CONFIG_I8042_KBD
Standard PC keyboard driver with US (is default) and
GERMAN key layout (switch via environment 'keymap=de') support.
Export function i8042_kbd_init, i8042_tstc and i8042_getc
for cfb_console. Supports cursor blinking.

- Video support:
CONFIG_VIDEO

Define this to enable video support (for output to
video).

CONFIG_VIDEO_CT69000

Enable Chips & Technologies 69000 Video chip

CONFIG_VIDEO_SMI_LYNXEM
Enable Silicon Motion SMI 712/710/810 Video chip. The
video output is selected via environment 'videoout'
(1 = LCD and 2 = CRT). If videoout is undefined, CRT is
assumed.

For the CT69000 and SMI_LYNXEM drivers, videomode is
selected via environment 'videomode'. Two diferent ways
are possible:
- "videomode=num" 'num' is a standard LiLo mode numbers.
Following standard modes are supported (* is default):

Colors 640x480 800x600 1024x768 1152x864 1280x1024
-------------+---------------------------------------------
8 bits | 0x301* 0x303 0x305 0x161 0x307
15 bits | 0x310 0x313 0x316 0x162 0x319
16 bits | 0x311 0x314 0x317 0x163 0x31A
24 bits | 0x312 0x315 0x318 ? 0x31B
-------------+---------------------------------------------
(i.e. setenv videomode 317; saveenv; reset;)

- "videomode=bootargs" all the video parameters are parsed
from the bootargs. (See drivers/video/videomodes.c)


CONFIG_VIDEO_SED13806
Enable Epson SED13806 driver. This driver supports 8bpp
and 16bpp modes defined by CONFIG_VIDEO_SED13806_8BPP
or CONFIG_VIDEO_SED13806_16BPP

- Keyboard Support:
CONFIG_KEYBOARD

Define this to enable a custom keyboard support.
This simply calls drv_keyboard_init() which must be
defined in your board-specific files.
The only board using this so far is RBC823.

- LCD Support: CONFIG_LCD

Define this to enable LCD support (for output to LCD
display); also select one of the supported displays
by defining one of these:

CONFIG_NEC_NL6448AC33:

NEC NL6448AC33-18. Active, color, single scan.

CONFIG_NEC_NL6448BC20

NEC NL6448BC20-08. 6.5", 640x480.
Active, color, single scan.

CONFIG_NEC_NL6448BC33_54

NEC NL6448BC33-54. 10.4", 640x480.
Active, color, single scan.

CONFIG_SHARP_16x9

Sharp 320x240. Active, color, single scan.
It isn't 16x9, and I am not sure what it is.

CONFIG_SHARP_LQ64D341

Sharp LQ64D341 display, 640x480.
Active, color, single scan.

CONFIG_HLD1045

HLD1045 display, 640x480.
Active, color, single scan.

CONFIG_OPTREX_BW

Optrex CBL50840-2 NF-FW 99 22 M5
or
Hitachi LMG6912RPFC-00T
or
Hitachi SP14Q002

320x240. Black & white.

Normally display is black on white background; define
CFG_WHITE_ON_BLACK to get it inverted.

- Splash Screen Support: CONFIG_SPLASH_SCREEN

If this option is set, the environment is checked for
a variable "splashimage". If found, the usual display
of logo, copyright and system information on the LCD
is suppressed and the BMP image at the address
specified in "splashimage" is loaded instead. The
console is redirected to the "nulldev", too. This
allows for a "silent" boot where a splash screen is
loaded very quickly after power-on.

- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP

If this option is set, additionally to standard BMP
images, gzipped BMP images can be displayed via the
splashscreen support or the bmp command.

- Compression support:
CONFIG_BZIP2

If this option is set, support for bzip2 compressed
images is included. If not, only uncompressed and gzip
compressed images are supported.

NOTE: the bzip2 algorithm requires a lot of RAM, so
the malloc area (as defined by CFG_MALLOC_LEN) should
be at least 4MB.

- MII/PHY support:
CONFIG_PHY_ADDR

The address of PHY on MII bus.

CONFIG_PHY_CLOCK_FREQ (ppc4xx)

The clock frequency of the MII bus

CONFIG_PHY_GIGE

If this option is set, support for speed/duplex
detection of Gigabit PHY is included.

CONFIG_PHY_RESET_DELAY

Some PHY like Intel LXT971A need extra delay after
reset before any MII register access is possible.
For such PHY, set this option to the usec delay
required. (minimum 300usec for LXT971A)

CONFIG_PHY_CMD_DELAY (ppc4xx)

Some PHY like Intel LXT971A need extra delay after
command issued before MII status register can be read

- Ethernet address:
CONFIG_ETHADDR
CONFIG_ETH2ADDR
CONFIG_ETH3ADDR

Define a default value for ethernet address to use
for the respective ethernet interface, in case this
is not determined automatically.

- IP address:
CONFIG_IPADDR

Define a default value for the IP address to use for
the default ethernet interface, in case this is not
determined through e.g. bootp.

- Server IP address:
CONFIG_SERVERIP

Defines a default value for theIP address of a TFTP
server to contact when using the "tftboot" command.

- Multicast TFTP Mode:
CONFIG_MCAST_TFTP

Defines whether you want to support multicast TFTP as per
rfc-2090; for example to work with atftp. Lets lots of targets
tftp down the same boot image concurrently. Note: the ethernet
driver in use must provide a function: mcast() to join/leave a
multicast group.

CONFIG_BOOTP_RANDOM_DELAY
- BOOTP Recovery Mode:
CONFIG_BOOTP_RANDOM_DELAY

If you have many targets in a network that try to
boot using BOOTP, you may want to avoid that all
systems send out BOOTP requests at precisely the same
moment (which would happen for instance at recovery
from a power failure, when all systems will try to
boot, thus flooding the BOOTP server. Defining
CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
inserted before sending out BOOTP requests. The
following delays are inserted then:

1st BOOTP request: delay 0 ... 1 sec
2nd BOOTP request: delay 0 ... 2 sec
3rd BOOTP request: delay 0 ... 4 sec
4th and following
BOOTP requests: delay 0 ... 8 sec

- DHCP Advanced Options:
You can fine tune the DHCP functionality by defining
CONFIG_BOOTP_* symbols:

CONFIG_BOOTP_SUBNETMASK
CONFIG_BOOTP_GATEWAY
CONFIG_BOOTP_HOSTNAME
CONFIG_BOOTP_NISDOMAIN
CONFIG_BOOTP_BOOTPATH
CONFIG_BOOTP_BOOTFILESIZE
CONFIG_BOOTP_DNS
CONFIG_BOOTP_DNS2
CONFIG_BOOTP_SEND_HOSTNAME
CONFIG_BOOTP_NTPSERVER
CONFIG_BOOTP_TIMEOFFSET
CONFIG_BOOTP_VENDOREX

CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
environment variable, not the BOOTP server.

CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
serverip from a DHCP server, it is possible that more
than one DNS serverip is offered to the client.
If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
serverip will be stored in the additional environment
variable "dnsip2". The first DNS serverip is always
stored in the variable "dnsip", when CONFIG_BOOTP_DNS
is defined.

CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
to do a dynamic update of a DNS server. To do this, they
need the hostname of the DHCP requester.
If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
of the "hostname" environment variable is passed as
option 12 to the DHCP server.

- CDP Options:
CONFIG_CDP_DEVICE_ID

The device id used in CDP trigger frames.

CONFIG_CDP_DEVICE_ID_PREFIX

A two character string which is prefixed to the MAC address
of the device.

CONFIG_CDP_PORT_ID

A printf format string which contains the ascii name of
the port. Normally is set to "eth%d" which sets
eth0 for the first ethernet, eth1 for the second etc.

CONFIG_CDP_CAPABILITIES

A 32bit integer which indicates the device capabilities;
0x00000010 for a normal host which does not forwards.

CONFIG_CDP_VERSION

An ascii string containing the version of the software.

CONFIG_CDP_PLATFORM

An ascii string containing the name of the platform.

CONFIG_CDP_TRIGGER

A 32bit integer sent on the trigger.

CONFIG_CDP_POWER_CONSUMPTION

A 16bit integer containing the power consumption of the
device in .1 of milliwatts.

CONFIG_CDP_APPLIANCE_VLAN_TYPE

A byte containing the id of the VLAN.

- Status LED: CONFIG_STATUS_LED

Several configurations allow to display the current
status using a LED. For instance, the LED will blink
fast while running U-Boot code, stop blinking as
soon as a reply to a BOOTP request was received, and
start blinking slow once the Linux kernel is running
(supported by a status LED driver in the Linux
kernel). Defining CONFIG_STATUS_LED enables this
feature in U-Boot.

- CAN Support: CONFIG_CAN_DRIVER

Defining CONFIG_CAN_DRIVER enables CAN driver support
on those systems that support this (optional)
feature, like the TQM8xxL modules.

- I2C Support: CONFIG_HARD_I2C | CONFIG_SOFT_I2C

These enable I2C serial bus commands. Defining either of
(but not both of) CONFIG_HARD_I2C or CONFIG_SOFT_I2C will
include the appropriate I2C driver for the selected cpu.

This will allow you to use i2c commands at the u-boot
command line (as long as you set CONFIG_CMD_I2C in
CONFIG_COMMANDS) and communicate with i2c based realtime
clock chips. See common/cmd_i2c.c for a description of the
command line interface.

CONFIG_I2C_CMD_TREE is a recommended option that places
all I2C commands under a single 'i2c' root command. The
older 'imm', 'imd', 'iprobe' etc. commands are considered
deprecated and may disappear in the future.

CONFIG_HARD_I2C selects a hardware I2C controller.

CONFIG_SOFT_I2C configures u-boot to use a software (aka
bit-banging) driver instead of CPM or similar hardware
support for I2C.

There are several other quantities that must also be
defined when you define CONFIG_HARD_I2C or CONFIG_SOFT_I2C.

In both cases you will need to define CFG_I2C_SPEED
to be the frequency (in Hz) at which you wish your i2c bus
to run and CFG_I2C_SLAVE to be the address of this node (ie
the cpu's i2c node address).

Now, the u-boot i2c code for the mpc8xx (cpu/mpc8xx/i2c.c)
sets the cpu up as a master node and so its address should
therefore be cleared to 0 (See, eg, MPC823e User's Manual
p.16-473). So, set CFG_I2C_SLAVE to 0.

That's all that's required for CONFIG_HARD_I2C.

If you use the software i2c interface (CONFIG_SOFT_I2C)
then the following macros need to be defined (examples are
from include/configs/lwmon.h):

I2C_INIT

(Optional). Any commands necessary to enable the I2C
controller or configure ports.

eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL)

I2C_PORT

(Only for MPC8260 CPU). The I/O port to use (the code
assumes both bits are on the same port). Valid values
are 0..3 for ports A..D.

I2C_ACTIVE

The code necessary to make the I2C data line active
(driven). If the data line is open collector, this
define can be null.

eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA)

I2C_TRISTATE

The code necessary to make the I2C data line tri-stated
(inactive). If the data line is open collector, this
define can be null.

eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)

I2C_READ

Code that returns TRUE if the I2C data line is high,
FALSE if it is low.

eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)

I2C_SDA(bit)

If <bit> is TRUE, sets the I2C data line high. If it
is FALSE, it clears it (low).

eg: #define I2C_SDA(bit) \
if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \
else immr->im_cpm.cp_pbdat &= ~PB_SDA

I2C_SCL(bit)

If <bit> is TRUE, sets the I2C clock line high. If it
is FALSE, it clears it (low).

eg: #define I2C_SCL(bit) \
if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \
else immr->im_cpm.cp_pbdat &= ~PB_SCL

I2C_DELAY

This delay is invoked four times per clock cycle so this
controls the rate of data transfer. The data rate thus
is 1 / (I2C_DELAY * 4). Often defined to be something
like:

#define I2C_DELAY udelay(2)

CFG_I2C_INIT_BOARD

When a board is reset during an i2c bus transfer
chips might think that the current transfer is still
in progress. On some boards it is possible to access
the i2c SCLK line directly, either by using the
processor pin as a GPIO or by having a second pin
connected to the bus. If this option is defined a
custom i2c_init_board() routine in boards/xxx/board.c
is run early in the boot sequence.

CONFIG_I2CFAST (PPC405GP|PPC405EP only)

This option enables configuration of bi_iic_fast[] flags
in u-boot bd_info structure based on u-boot environment
variable "i2cfast". (see also i2cfast)

CONFIG_I2C_MULTI_BUS

This option allows the use of multiple I2C buses, each of which
must have a controller. At any point in time, only one bus is
active. To switch to a different bus, use the 'i2c dev' command.
Note that bus numbering is zero-based.

CFG_I2C_NOPROBES

This option specifies a list of I2C devices that will be skipped
when the 'i2c probe' command is issued (or 'iprobe' using the legacy
command). If CONFIG_I2C_MULTI_BUS is set, specify a list of bus-device
pairs. Otherwise, specify a 1D array of device addresses

e.g.
#undef CONFIG_I2C_MULTI_BUS
#define CFG_I2C_NOPROBES {0x50,0x68}

will skip addresses 0x50 and 0x68 on a board with one I2C bus

#define CONFIG_I2C_MULTI_BUS
#define CFG_I2C_MULTI_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}

will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1

CFG_SPD_BUS_NUM

If defined, then this indicates the I2C bus number for DDR SPD.
If not defined, then U-Boot assumes that SPD is on I2C bus 0.

CFG_RTC_BUS_NUM

If defined, then this indicates the I2C bus number for the RTC.
If not defined, then U-Boot assumes that RTC is on I2C bus 0.

CFG_DTT_BUS_NUM

If defined, then this indicates the I2C bus number for the DTT.
If not defined, then U-Boot assumes that DTT is on I2C bus 0.

CONFIG_FSL_I2C

Define this option if you want to use Freescale's I2C driver in
drivers/i2c/fsl_i2c.c.


- SPI Support: CONFIG_SPI

Enables SPI driver (so far only tested with
SPI EEPROM, also an instance works with Crystal A/D and
D/As on the SACSng board)

CONFIG_SPI_X

Enables extended (16-bit) SPI EEPROM addressing.
(symmetrical to CONFIG_I2C_X)

CONFIG_SOFT_SPI

Enables a software (bit-bang) SPI driver rather than
using hardware support. This is a general purpose
driver that only requires three general I/O port pins
(two outputs, one input) to function. If this is
defined, the board configuration must define several
SPI configuration items (port pins to use, etc). For
an example, see include/configs/sacsng.h.

CONFIG_HARD_SPI

Enables a hardware SPI driver for general-purpose reads
and writes. As with CONFIG_SOFT_SPI, the board configuration
must define a list of chip-select function pointers.
Currently supported on some MPC8xxx processors. For an
example, see include/configs/mpc8349emds.h.

- FPGA Support: CONFIG_FPGA

Enables FPGA subsystem.

CONFIG_FPGA_<vendor>

Enables support for specific chip vendors.
(ALTERA, XILINX)

CONFIG_FPGA_<family>

Enables support for FPGA family.
(SPARTAN2, SPARTAN3, VIRTEX2, CYCLONE2, ACEX1K, ACEX)

CONFIG_FPGA_COUNT

Specify the number of FPGA devices to support.

CFG_FPGA_PROG_FEEDBACK

Enable printing of hash marks during FPGA configuration.

CFG_FPGA_CHECK_BUSY

Enable checks on FPGA configuration interface busy
status by the configuration function. This option
will require a board or device specific function to
be written.

CONFIG_FPGA_DELAY

If defined, a function that provides delays in the FPGA
configuration driver.

CFG_FPGA_CHECK_CTRLC
Allow Control-C to interrupt FPGA configuration

CFG_FPGA_CHECK_ERROR

Check for configuration errors during FPGA bitfile
loading. For example, abort during Virtex II
configuration if the INIT_B line goes low (which
indicated a CRC error).

CFG_FPGA_WAIT_INIT

Maximum time to wait for the INIT_B line to deassert
after PROB_B has been deasserted during a Virtex II
FPGA configuration sequence. The default time is 500
mS.

CFG_FPGA_WAIT_BUSY

Maximum time to wait for BUSY to deassert during
Virtex II FPGA configuration. The default is 5 mS.

CFG_FPGA_WAIT_CONFIG

Time to wait after FPGA configuration. The default is
200 mS.

- Configuration Management:
CONFIG_IDENT_STRING

If defined, this string will be added to the U-Boot
version information (U_BOOT_VERSION)

- Vendor Parameter Protection:

U-Boot considers the values of the environment
variables "serial#" (Board Serial Number) and
"ethaddr" (Ethernet Address) to be parameters that
are set once by the board vendor / manufacturer, and
protects these variables from casual modification by
the user. Once set, these variables are read-only,
and write or delete attempts are rejected. You can
change this behviour:

If CONFIG_ENV_OVERWRITE is #defined in your config
file, the write protection for vendor parameters is
completely disabled. Anybody can change or delete
these parameters.

Alternatively, if you #define _both_ CONFIG_ETHADDR
_and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
ethernet address is installed in the environment,
which can be changed exactly ONCE by the user. [The
serial# is unaffected by this, i. e. it remains
read-only.]

- Protected RAM:
CONFIG_PRAM

Define this variable to enable the reservation of
"protected RAM", i. e. RAM which is not overwritten
by U-Boot. Define CONFIG_PRAM to hold the number of
kB you want to reserve for pRAM. You can overwrite
this default value by defining an environment
variable "pram" to the number of kB you want to
reserve. Note that the board info structure will
still show the full amount of RAM. If pRAM is
reserved, a new environment variable "mem" will
automatically be defined to hold the amount of
remaining RAM in a form that can be passed as boot
argument to Linux, for instance like that:

setenv bootargs ... mem=\${mem}
saveenv

This way you can tell Linux not to use this memory,
either, which results in a memory region that will
not be affected by reboots.

*WARNING* If your board configuration uses automatic
detection of the RAM size, you must make sure that
this memory test is non-destructive. So far, the
following board configurations are known to be
"pRAM-clean":

ETX094, IVMS8, IVML24, SPD8xx, TQM8xxL,
HERMES, IP860, RPXlite, LWMON, LANTEC,
PCU_E, FLAGADM, TQM8260

- Error Recovery:
CONFIG_PANIC_HANG

Define this variable to stop the system in case of a
fatal error, so that you have to reset it manually.
This is probably NOT a good idea for an embedded
system where you want to system to reboot
automatically as fast as possible, but it may be
useful during development since you can try to debug
the conditions that lead to the situation.

CONFIG_NET_RETRY_COUNT

This variable defines the number of retries for
network operations like ARP, RARP, TFTP, or BOOTP
before giving up the operation. If not defined, a
default value of 5 is used.

- Command Interpreter:
CONFIG_AUTO_COMPLETE

Enable auto completion of commands using TAB.

Note that this feature has NOT been implemented yet
for the "hush" shell.


CFG_HUSH_PARSER

Define this variable to enable the "hush" shell (from
Busybox) as command line interpreter, thus enabling
powerful command line syntax like
if...then...else...fi conditionals or `&&' and '||'
constructs ("shell scripts").

If undefined, you get the old, much simpler behaviour
with a somewhat smaller memory footprint.


CFG_PROMPT_HUSH_PS2

This defines the secondary prompt string, which is
printed when the command interpreter needs more input
to complete a command. Usually "> ".

Note:

In the current implementation, the local variables
space and global environment variables space are
separated. Local variables are those you define by
simply typing `name=value'. To access a local
variable later on, you have write `$name' or
`${name}'; to execute the contents of a variable
directly type `$name' at the command prompt.

Global environment variables are those you use
setenv/printenv to work with. To run a command stored
in such a variable, you need to use the run command,
and you must not use the '$' sign to access them.

To store commands and special characters in a
variable, please use double quotation marks
surrounding the whole text of the variable, instead
of the backslashes before semicolons and special
symbols.

- Commandline Editing and History:
CONFIG_CMDLINE_EDITING

Enable editiong and History functions for interactive
commandline input operations

- Default Environment:
CONFIG_EXTRA_ENV_SETTINGS

Define this to contain any number of null terminated
strings (variable = value pairs) that will be part of
the default environment compiled into the boot image.

For example, place something like this in your
board's config file:

#define CONFIG_EXTRA_ENV_SETTINGS \
"myvar1=value1\0" \
"myvar2=value2\0"

Warning: This method is based on knowledge about the
internal format how the environment is stored by the
U-Boot code. This is NOT an official, exported
interface! Although it is unlikely that this format
will change soon, there is no guarantee either.
You better know what you are doing here.

Note: overly (ab)use of the default environment is
discouraged. Make sure to check other ways to preset
the environment like the autoscript function or the
boot command first.

- DataFlash Support:
CONFIG_HAS_DATAFLASH

Defining this option enables DataFlash features and
allows to read/write in Dataflash via the standard
commands cp, md...

- SystemACE Support:
CONFIG_SYSTEMACE

Adding this option adds support for Xilinx SystemACE
chips attached via some sort of local bus. The address
of the chip must alsh be defined in the
CFG_SYSTEMACE_BASE macro. For example:

#define CONFIG_SYSTEMACE
#define CFG_SYSTEMACE_BASE 0xf0000000

When SystemACE support is added, the "ace" device type
becomes available to the fat commands, i.e. fatls.

- TFTP Fixed UDP Port:
CONFIG_TFTP_PORT

If this is defined, the environment variable tftpsrcp
is used to supply the TFTP UDP source port value.
If tftpsrcp isn't defined, the normal pseudo-random port
number generator is used.

Also, the environment variable tftpdstp is used to supply
the TFTP UDP destination port value. If tftpdstp isn't
defined, the normal port 69 is used.

The purpose for tftpsrcp is to allow a TFTP server to
blindly start the TFTP transfer using the pre-configured
target IP address and UDP port. This has the effect of
"punching through" the (Windows XP) firewall, allowing
the remainder of the TFTP transfer to proceed normally.
A better solution is to properly configure the firewall,
but sometimes that is not allowed.

- Show boot progress:
CONFIG_SHOW_BOOT_PROGRESS

Defining this option allows to add some board-
specific code (calling a user-provided function
"show_boot_progress(int)") that enables you to show
the system's boot progress on some display (for
example, some LED's) on your board. At the moment,
the following checkpoints are implemented:

Arg Where When
1 common/cmd_bootm.c before attempting to boot an image
-1 common/cmd_bootm.c Image header has bad magic number
2 common/cmd_bootm.c Image header has correct magic number
-2 common/cmd_bootm.c Image header has bad checksum
3 common/cmd_bootm.c Image header has correct checksum
-3 common/cmd_bootm.c Image data has bad checksum
4 common/cmd_bootm.c Image data has correct checksum
-4 common/cmd_bootm.c Image is for unsupported architecture
5 common/cmd_bootm.c Architecture check OK
-5 common/cmd_bootm.c Wrong Image Type (not kernel, multi, standalone)
6 common/cmd_bootm.c Image Type check OK
-6 common/cmd_bootm.c gunzip uncompression error
-7 common/cmd_bootm.c Unimplemented compression type
7 common/cmd_bootm.c Uncompression OK
-8 common/cmd_bootm.c Wrong Image Type (not kernel, multi, standalone)
8 common/cmd_bootm.c Image Type check OK
-9 common/cmd_bootm.c Unsupported OS (not Linux, BSD, VxWorks, QNX)
9 common/cmd_bootm.c Start initial ramdisk verification
-10 common/cmd_bootm.c Ramdisk header has bad magic number
-11 common/cmd_bootm.c Ramdisk header has bad checksum
10 common/cmd_bootm.c Ramdisk header is OK
-12 common/cmd_bootm.c Ramdisk data has bad checksum
11 common/cmd_bootm.c Ramdisk data has correct checksum
12 common/cmd_bootm.c Ramdisk verification complete, start loading
-13 common/cmd_bootm.c Wrong Image Type (not PPC Linux Ramdisk)
13 common/cmd_bootm.c Start multifile image verification
14 common/cmd_bootm.c No initial ramdisk, no multifile, continue.
15 common/cmd_bootm.c All preparation done, transferring control to OS

-30 lib_ppc/board.c Fatal error, hang the system
-31 post/post.c POST test failed, detected by post_output_backlog()
-32 post/post.c POST test failed, detected by post_run_single()

34 common/cmd_doc.c before loading a Image from a DOC device
-35 common/cmd_doc.c Bad usage of "doc" command
35 common/cmd_doc.c correct usage of "doc" command
-36 common/cmd_doc.c No boot device
36 common/cmd_doc.c correct boot device
-37 common/cmd_doc.c Unknown Chip ID on boot device
37 common/cmd_doc.c correct chip ID found, device available
-38 common/cmd_doc.c Read Error on boot device
38 common/cmd_doc.c reading Image header from DOC device OK
-39 common/cmd_doc.c Image header has bad magic number
39 common/cmd_doc.c Image header has correct magic number
-40 common/cmd_doc.c Error reading Image from DOC device
40 common/cmd_doc.c Image header has correct magic number
41 common/cmd_ide.c before loading a Image from a IDE device
-42 common/cmd_ide.c Bad usage of "ide" command
42 common/cmd_ide.c correct usage of "ide" command
-43 common/cmd_ide.c No boot device
43 common/cmd_ide.c boot device found
-44 common/cmd_ide.c Device not available
44 common/cmd_ide.c Device available
-45 common/cmd_ide.c wrong partition selected
45 common/cmd_ide.c partition selected
-46 common/cmd_ide.c Unknown partition table
46 common/cmd_ide.c valid partition table found
-47 common/cmd_ide.c Invalid partition type
47 common/cmd_ide.c correct partition type
-48 common/cmd_ide.c Error reading Image Header on boot device
48 common/cmd_ide.c reading Image Header from IDE device OK
-49 common/cmd_ide.c Image header has bad magic number
49 common/cmd_ide.c Image header has correct magic number
-50 common/cmd_ide.c Image header has bad checksum
50 common/cmd_ide.c Image header has correct checksum
-51 common/cmd_ide.c Error reading Image from IDE device
51 common/cmd_ide.c reading Image from IDE device OK
52 common/cmd_nand.c before loading a Image from a NAND device
-53 common/cmd_nand.c Bad usage of "nand" command
53 common/cmd_nand.c correct usage of "nand" command
-54 common/cmd_nand.c No boot device
54 common/cmd_nand.c boot device found
-55 common/cmd_nand.c Unknown Chip ID on boot device
55 common/cmd_nand.c correct chip ID found, device available
-56 common/cmd_nand.c Error reading Image Header on boot device
56 common/cmd_nand.c reading Image Header from NAND device OK
-57 common/cmd_nand.c Image header has bad magic number
57 common/cmd_nand.c Image header has correct magic number
-58 common/cmd_nand.c Error reading Image from NAND device
58 common/cmd_nand.c reading Image from NAND device OK

-60 common/env_common.c Environment has a bad CRC, using default

64 net/eth.c starting with Ethernetconfiguration.
-64 net/eth.c no Ethernet found.
65 net/eth.c Ethernet found.

-80 common/cmd_net.c usage wrong
80 common/cmd_net.c before calling NetLoop()
-81 common/cmd_net.c some error in NetLoop() occured
81 common/cmd_net.c NetLoop() back without error
-82 common/cmd_net.c size == 0 (File with size 0 loaded)
82 common/cmd_net.c trying automatic boot
83 common/cmd_net.c running autoscript
-83 common/cmd_net.c some error in automatic boot or autoscript
84 common/cmd_net.c end without errors

Modem Support:
--------------

[so far only for SMDK2400 and TRAB boards]

- Modem support endable:
CONFIG_MODEM_SUPPORT

- RTS/CTS Flow control enable:
CONFIG_HWFLOW

- Modem debug support:
CONFIG_MODEM_SUPPORT_DEBUG

Enables debugging stuff (char screen[1024], dbg())
for modem support. Useful only with BDI2000.

- Interrupt support (PPC):

There are common interrupt_init() and timer_interrupt()
for all PPC archs. interrupt_init() calls interrupt_init_cpu()
for cpu specific initialization. interrupt_init_cpu()
should set decrementer_count to appropriate value. If
cpu resets decrementer automatically after interrupt
(ppc4xx) it should set decrementer_count to zero.
timer_interrupt() calls timer_interrupt_cpu() for cpu
specific handling. If board has watchdog / status_led
/ other_activity_monitor it works automatically from
general timer_interrupt().

- General:

In the target system modem support is enabled when a
specific key (key combination) is pressed during
power-on. Otherwise U-Boot will boot normally
(autoboot). The key_pressed() fuction is called from
board_init(). Currently key_pressed() is a dummy
function, returning 1 and thus enabling modem
initialization.

If there are no modem init strings in the
environment, U-Boot proceed to autoboot; the
previous output (banner, info printfs) will be
supressed, though.

See also: doc/README.Modem


Configuration Settings:
-----------------------

- CFG_LONGHELP: Defined when you want long help messages included;
undefine this when you're short of memory.

- CFG_PROMPT: This is what U-Boot prints on the console to
prompt for user input.

- CFG_CBSIZE: Buffer size for input from the Console

- CFG_PBSIZE: Buffer size for Console output

- CFG_MAXARGS: max. Number of arguments accepted for monitor commands

- CFG_BARGSIZE: Buffer size for Boot Arguments which are passed to
the application (usually a Linux kernel) when it is
booted

- CFG_BAUDRATE_TABLE:
List of legal baudrate settings for this board.

- CFG_CONSOLE_INFO_QUIET
Suppress display of console information at boot.

- CFG_CONSOLE_IS_IN_ENV
If the board specific function
extern int overwrite_console (void);
returns 1, the stdin, stderr and stdout are switched to the
serial port, else the settings in the environment are used.

- CFG_CONSOLE_OVERWRITE_ROUTINE
Enable the call to overwrite_console().

- CFG_CONSOLE_ENV_OVERWRITE
Enable overwrite of previous console environment settings.

- CFG_MEMTEST_START, CFG_MEMTEST_END:
Begin and End addresses of the area used by the
simple memory test.

- CFG_ALT_MEMTEST:
Enable an alternate, more extensive memory test.

- CFG_MEMTEST_SCRATCH:
Scratch address used by the alternate memory test
You only need to set this if address zero isn't writeable

- CFG_TFTP_LOADADDR:
Default load address for network file downloads

- CFG_LOADS_BAUD_CHANGE:
Enable temporary baudrate change while serial download

- CFG_SDRAM_BASE:
Physical start address of SDRAM. _Must_ be 0 here.

- CFG_MBIO_BASE:
Physical start address of Motherboard I/O (if using a
Cogent motherboard)

- CFG_FLASH_BASE:
Physical start address of Flash memory.

- CFG_MONITOR_BASE:
Physical start address of boot monitor code (set by
make config files to be same as the text base address
(TEXT_BASE) used when linking) - same as
CFG_FLASH_BASE when booting from flash.

- CFG_MONITOR_LEN:
Size of memory reserved for monitor code, used to
determine _at_compile_time_ (!) if the environment is
embedded within the U-Boot image, or in a separate
flash sector.

- CFG_MALLOC_LEN:
Size of DRAM reserved for malloc() use.

- CFG_BOOTM_LEN:
Normally compressed uImages are limited to an
uncompressed size of 8 MBytes. If this is not enough,
you can define CFG_BOOTM_LEN in your board config file
to adjust this setting to your needs.

- CFG_BOOTMAPSZ:
Maximum size of memory mapped by the startup code of
the Linux kernel; all data that must be processed by
the Linux kernel (bd_info, boot arguments, eventually
initrd image) must be put below this limit.

- CFG_MAX_FLASH_BANKS:
Max number of Flash memory banks

- CFG_MAX_FLASH_SECT:
Max number of sectors on a Flash chip

- CFG_FLASH_ERASE_TOUT:
Timeout for Flash erase operations (in ms)

- CFG_FLASH_WRITE_TOUT:
Timeout for Flash write operations (in ms)

- CFG_FLASH_LOCK_TOUT
Timeout for Flash set sector lock bit operation (in ms)

- CFG_FLASH_UNLOCK_TOUT
Timeout for Flash clear lock bits operation (in ms)

- CFG_FLASH_PROTECTION
If defined, hardware flash sectors protection is used
instead of U-Boot software protection.

- CFG_DIRECT_FLASH_TFTP:

Enable TFTP transfers directly to flash memory;
without this option such a download has to be
performed in two steps: (1) download to RAM, and (2)
copy from RAM to flash.

The two-step approach is usually more reliable, since
you can check if the download worked before you erase
the flash, but in some situations (when sytem RAM is
too limited to allow for a tempory copy of the
downloaded image) this option may be very useful.

- CFG_FLASH_CFI:
Define if the flash driver uses extra elements in the
common flash structure for storing flash geometry.

- CFG_FLASH_CFI_DRIVER
This option also enables the building of the cfi_flash driver
in the drivers directory

- CFG_FLASH_QUIET_TEST
If this option is defined, the common CFI flash doesn't
print it's warning upon not recognized FLASH banks. This
is useful, if some of the configured banks are only
optionally available.

- CFG_RX_ETH_BUFFER:
Defines the number of ethernet receive buffers. On some
ethernet controllers it is recommended to set this value
to 8 or even higher (EEPRO100 or 405 EMAC), since all
buffers can be full shortly after enabling the interface
on high ethernet traffic.
Defaults to 4 if not defined.

The following definitions that deal with the placement and management
of environment data (variable area); in general, we support the
following configurations:

- CFG_ENV_IS_IN_FLASH:

Define this if the environment is in flash memory.

a) The environment occupies one whole flash sector, which is
"embedded" in the text segment with the U-Boot code. This
happens usually with "bottom boot sector" or "top boot
sector" type flash chips, which have several smaller
sectors at the start or the end. For instance, such a
layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
such a case you would place the environment in one of the
4 kB sectors - with U-Boot code before and after it. With
"top boot sector" type flash chips, you would put the
environment in one of the last sectors, leaving a gap
between U-Boot and the environment.

- CFG_ENV_OFFSET:

Offset of environment data (variable area) to the
beginning of flash memory; for instance, with bottom boot
type flash chips the second sector can be used: the offset
for this sector is given here.

CFG_ENV_OFFSET is used relative to CFG_FLASH_BASE.

- CFG_ENV_ADDR:

This is just another way to specify the start address of
the flash sector containing the environment (instead of
CFG_ENV_OFFSET).

- CFG_ENV_SECT_SIZE:

Size of the sector containing the environment.


b) Sometimes flash chips have few, equal sized, BIG sectors.
In such a case you don't want to spend a whole sector for
the environment.

- CFG_ENV_SIZE:

If you use this in combination with CFG_ENV_IS_IN_FLASH
and CFG_ENV_SECT_SIZE, you can specify to use only a part
of this flash sector for the environment. This saves
memory for the RAM copy of the environment.

It may also save flash memory if you decide to use this
when your environment is "embedded" within U-Boot code,
since then the remainder of the flash sector could be used
for U-Boot code. It should be pointed out that this is
STRONGLY DISCOURAGED from a robustness point of view:
updating the environment in flash makes it always
necessary to erase the WHOLE sector. If something goes
wrong before the contents has been restored from a copy in
RAM, your target system will be dead.

- CFG_ENV_ADDR_REDUND
CFG_ENV_SIZE_REDUND

These settings describe a second storage area used to hold
a redundand copy of the environment data, so that there is
a valid backup copy in case there is a power failure during
a "saveenv" operation.

BE CAREFUL! Any changes to the flash layout, and some changes to the
source code will make it necessary to adapt <board>/u-boot.lds*
accordingly!


- CFG_ENV_IS_IN_NVRAM:

Define this if you have some non-volatile memory device
(NVRAM, battery buffered SRAM) which you want to use for the
environment.

- CFG_ENV_ADDR:
- CFG_ENV_SIZE:

These two #defines are used to determin the memory area you
want to use for environment. It is assumed that this memory
can just be read and written to, without any special
provision.

BE CAREFUL! The first access to the environment happens quite early
in U-Boot initalization (when we try to get the setting of for the
console baudrate). You *MUST* have mappend your NVRAM area then, or
U-Boot will hang.

Please note that even with NVRAM we still use a copy of the
environment in RAM: we could work on NVRAM directly, but we want to
keep settings there always unmodified except somebody uses "saveenv"
to save the current settings.


- CFG_ENV_IS_IN_EEPROM:

Use this if you have an EEPROM or similar serial access
device and a driver for it.

- CFG_ENV_OFFSET:
- CFG_ENV_SIZE:

These two #defines specify the offset and size of the
environment area within the total memory of your EEPROM.

- CFG_I2C_EEPROM_ADDR:
If defined, specified the chip address of the EEPROM device.
The default address is zero.

- CFG_EEPROM_PAGE_WRITE_BITS:
If defined, the number of bits used to address bytes in a
single page in the EEPROM device. A 64 byte page, for example
would require six bits.

- CFG_EEPROM_PAGE_WRITE_DELAY_MS:
If defined, the number of milliseconds to delay between
page writes. The default is zero milliseconds.

- CFG_I2C_EEPROM_ADDR_LEN:
The length in bytes of the EEPROM memory array address. Note
that this is NOT the chip address length!

- CFG_I2C_EEPROM_ADDR_OVERFLOW:
EEPROM chips that implement "address overflow" are ones
like Catalyst 24WC04/08/16 which has 9/10/11 bits of
address and the extra bits end up in the "chip address" bit
slots. This makes a 24WC08 (1Kbyte) chip look like four 256
byte chips.

Note that we consider the length of the address field to
still be one byte because the extra address bits are hidden
in the chip address.

- CFG_EEPROM_SIZE:
The size in bytes of the EEPROM device.


- CFG_ENV_IS_IN_DATAFLASH:

Define this if you have a DataFlash memory device which you
want to use for the environment.

- CFG_ENV_OFFSET:
- CFG_ENV_ADDR:
- CFG_ENV_SIZE:

These three #defines specify the offset and size of the
environment area within the total memory of your DataFlash placed
at the specified address.

- CFG_ENV_IS_IN_NAND:

Define this if you have a NAND device which you want to use
for the environment.

- CFG_ENV_OFFSET:
- CFG_ENV_SIZE:

These two #defines specify the offset and size of the environment
area within the first NAND device.

- CFG_ENV_OFFSET_REDUND

This setting describes a second storage area of CFG_ENV_SIZE
size used to hold a redundant copy of the environment data,
so that there is a valid backup copy in case there is a
power failure during a "saveenv" operation.

Note: CFG_ENV_OFFSET and CFG_ENV_OFFSET_REDUND must be aligned
to a block boundary, and CFG_ENV_SIZE must be a multiple of
the NAND devices block size.

- CFG_SPI_INIT_OFFSET

Defines offset to the initial SPI buffer area in DPRAM. The
area is used at an early stage (ROM part) if the environment
is configured to reside in the SPI EEPROM: We need a 520 byte
scratch DPRAM area. It is used between the two initialization
calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
to be a good choice since it makes it far enough from the
start of the data area as well as from the stack pointer.

Please note that the environment is read-only until the monitor
has been relocated to RAM and a RAM copy of the environment has been
created; also, when using EEPROM you will have to use getenv_r()
until then to read environment variables.

The environment is protected by a CRC32 checksum. Before the monitor
is relocated into RAM, as a result of a bad CRC you will be working
with the compiled-in default environment - *silently*!!! [This is
necessary, because the first environment variable we need is the
"baudrate" setting for the console - if we have a bad CRC, we don't
have any device yet where we could complain.]

Note: once the monitor has been relocated, then it will complain if
the default environment is used; a new CRC is computed as soon as you
use the "saveenv" command to store a valid environment.

- CFG_FAULT_ECHO_LINK_DOWN:
Echo the inverted Ethernet link state to the fault LED.

Note: If this option is active, then CFG_FAULT_MII_ADDR
also needs to be defined.

- CFG_FAULT_MII_ADDR:
MII address of the PHY to check for the Ethernet link state.

- CFG_64BIT_VSPRINTF:
Makes vsprintf (and all *printf functions) support printing
of 64bit values by using the L quantifier

- CFG_64BIT_STRTOUL:
Adds simple_strtoull that returns a 64bit value

Low Level (hardware related) configuration options:
---------------------------------------------------

- CFG_CACHELINE_SIZE:
Cache Line Size of the CPU.

- CFG_DEFAULT_IMMR:
Default address of the IMMR after system reset.

Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
and RPXsuper) to be able to adjust the position of
the IMMR register after a reset.

- Floppy Disk Support:
CFG_FDC_DRIVE_NUMBER

the default drive number (default value 0)

CFG_ISA_IO_STRIDE

defines the spacing between fdc chipset registers
(default value 1)

CFG_ISA_IO_OFFSET

defines the offset of register from address. It
depends on which part of the data bus is connected to
the fdc chipset. (default value 0)

If CFG_ISA_IO_STRIDE CFG_ISA_IO_OFFSET and
CFG_FDC_DRIVE_NUMBER are undefined, they take their
default value.

if CFG_FDC_HW_INIT is defined, then the function
fdc_hw_init() is called at the beginning of the FDC
setup. fdc_hw_init() must be provided by the board
source code. It is used to make hardware dependant
initializations.

- CFG_IMMR: Physical address of the Internal Memory.
DO NOT CHANGE unless you know exactly what you're
doing! (11-4) [MPC8xx/82xx systems only]

- CFG_INIT_RAM_ADDR:

Start address of memory area that can be used for
initial data and stack; please note that this must be
writable memory that is working WITHOUT special
initialization, i. e. you CANNOT use normal RAM which
will become available only after programming the
memory controller and running certain initialization
sequences.

U-Boot uses the following memory types:
- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
- MPC824X: data cache
- PPC4xx: data cache

- CFG_GBL_DATA_OFFSET:

Offset of the initial data structure in the memory
area defined by CFG_INIT_RAM_ADDR. Usually
CFG_GBL_DATA_OFFSET is chosen such that the initial
data is located at the end of the available space
(sometimes written as (CFG_INIT_RAM_END -
CFG_INIT_DATA_SIZE), and the initial stack is just
below that area (growing from (CFG_INIT_RAM_ADDR +
CFG_GBL_DATA_OFFSET) downward.

Note:
On the MPC824X (or other systems that use the data
cache for initial memory) the address chosen for
CFG_INIT_RAM_ADDR is basically arbitrary - it must
point to an otherwise UNUSED address space between
the top of RAM and the start of the PCI space.

- CFG_SIUMCR: SIU Module Configuration (11-6)

- CFG_SYPCR: System Protection Control (11-9)

- CFG_TBSCR: Time Base Status and Control (11-26)

- CFG_PISCR: Periodic Interrupt Status and Control (11-31)

- CFG_PLPRCR: PLL, Low-Power, and Reset Control Register (15-30)

- CFG_SCCR: System Clock and reset Control Register (15-27)

- CFG_OR_TIMING_SDRAM:
SDRAM timing

- CFG_MAMR_PTA:
periodic timer for refresh

- CFG_DER: Debug Event Register (37-47)

- FLASH_BASE0_PRELIM, FLASH_BASE1_PRELIM, CFG_REMAP_OR_AM,
CFG_PRELIM_OR_AM, CFG_OR_TIMING_FLASH, CFG_OR0_REMAP,
CFG_OR0_PRELIM, CFG_BR0_PRELIM, CFG_OR1_REMAP, CFG_OR1_PRELIM,
CFG_BR1_PRELIM:
Memory Controller Definitions: BR0/1 and OR0/1 (FLASH)

- SDRAM_BASE2_PRELIM, SDRAM_BASE3_PRELIM, SDRAM_MAX_SIZE,
CFG_OR_TIMING_SDRAM, CFG_OR2_PRELIM, CFG_BR2_PRELIM,
CFG_OR3_PRELIM, CFG_BR3_PRELIM:
Memory Controller Definitions: BR2/3 and OR2/3 (SDRAM)

- CFG_MAMR_PTA, CFG_MPTPR_2BK_4K, CFG_MPTPR_1BK_4K, CFG_MPTPR_2BK_8K,
CFG_MPTPR_1BK_8K, CFG_MAMR_8COL, CFG_MAMR_9COL:
Machine Mode Register and Memory Periodic Timer
Prescaler definitions (SDRAM timing)

- CFG_I2C_UCODE_PATCH, CFG_I2C_DPMEM_OFFSET [0x1FC0]:
enable I2C microcode relocation patch (MPC8xx);
define relocation offset in DPRAM [DSP2]

- CFG_SMC_UCODE_PATCH, CFG_SMC_DPMEM_OFFSET [0x1FC0]:
enable SMC microcode relocation patch (MPC8xx);
define relocation offset in DPRAM [SMC1]

- CFG_SPI_UCODE_PATCH, CFG_SPI_DPMEM_OFFSET [0x1FC0]:
enable SPI microcode relocation patch (MPC8xx);
define relocation offset in DPRAM [SCC4]

- CFG_USE_OSCCLK:
Use OSCM clock mode on MBX8xx board. Be careful,
wrong setting might damage your board. Read
doc/README.MBX before setting this variable!

- CFG_CPM_POST_WORD_ADDR: (MPC8xx, MPC8260 only)
Offset of the bootmode word in DPRAM used by post
(Power On Self Tests). This definition overrides
#define'd default value in commproc.h resp.
cpm_8260.h.

- CFG_PCI_SLV_MEM_LOCAL, CFG_PCI_SLV_MEM_BUS, CFG_PICMR0_MASK_ATTRIB,
CFG_PCI_MSTR0_LOCAL, CFG_PCIMSK0_MASK, CFG_PCI_MSTR1_LOCAL,
CFG_PCIMSK1_MASK, CFG_PCI_MSTR_MEM_LOCAL, CFG_PCI_MSTR_MEM_BUS,
CFG_CPU_PCI_MEM_START, CFG_PCI_MSTR_MEM_SIZE, CFG_POCMR0_MASK_ATTRIB,
CFG_PCI_MSTR_MEMIO_LOCAL, CFG_PCI_MSTR_MEMIO_BUS, CPU_PCI_MEMIO_START,
CFG_PCI_MSTR_MEMIO_SIZE, CFG_POCMR1_MASK_ATTRIB, CFG_PCI_MSTR_IO_LOCAL,
CFG_PCI_MSTR_IO_BUS, CFG_CPU_PCI_IO_START, CFG_PCI_MSTR_IO_SIZE,
CFG_POCMR2_MASK_ATTRIB: (MPC826x only)
Overrides the default PCI memory map in cpu/mpc8260/pci.c if set.

- CONFIG_SPD_EEPROM
Get DDR timing information from an I2C EEPROM. Common with pluggable
memory modules such as SODIMMs
SPD_EEPROM_ADDRESS
I2C address of the SPD EEPROM

- CFG_SPD_BUS_NUM
If SPD EEPROM is on an I2C bus other than the first one, specify here.
Note that the value must resolve to something your driver can deal with.

- CFG_83XX_DDR_USES_CS0
Only for 83xx systems. If specified, then DDR should be configured
using CS0 and CS1 instead of CS2 and CS3.

- CFG_83XX_DDR_USES_CS0
Only for 83xx systems. If specified, then DDR should be configured
using CS0 and CS1 instead of CS2 and CS3.

- CONFIG_ETHER_ON_FEC[12]
Define to enable FEC[12] on a 8xx series processor.

- CONFIG_FEC[12]_PHY
Define to the hardcoded PHY address which corresponds
to the given FEC; i. e.
#define CONFIG_FEC1_PHY 4
means that the PHY with address 4 is connected to FEC1

When set to -1, means to probe for first available.

- CONFIG_FEC[12]_PHY_NORXERR
The PHY does not have a RXERR line (RMII only).
(so program the FEC to ignore it).

- CONFIG_RMII
Enable RMII mode for all FECs.
Note that this is a global option, we can't
have one FEC in standard MII mode and another in RMII mode.

- CONFIG_CRC32_VERIFY
Add a verify option to the crc32 command.
The syntax is:

=> crc32 -v <address> <count> <crc32>

Where address/count indicate a memory area
and crc32 is the correct crc32 which the
area should have.

- CONFIG_LOOPW
Add the "loopw" memory command. This only takes effect if
the memory commands are activated globally (CONFIG_CMD_MEM).

- CONFIG_MX_CYCLIC
Add the "mdc" and "mwc" memory commands. These are cyclic
"md/mw" commands.
Examples:

=> mdc.b 10 4 500
This command will print 4 bytes (10,11,12,13) each 500 ms.

=> mwc.l 100 12345678 10
This command will write 12345678 to address 100 all 10 ms.

This only takes effect if the memory commands are activated
globally (CONFIG_CMD_MEM).

- CONFIG_SKIP_LOWLEVEL_INIT
- CONFIG_SKIP_RELOCATE_UBOOT

[ARM only] If these variables are defined, then
certain low level initializations (like setting up
the memory controller) are omitted and/or U-Boot does
not relocate itself into RAM.
Normally these variables MUST NOT be defined. The
only exception is when U-Boot is loaded (to RAM) by
some other boot loader or by a debugger which
performs these intializations itself.


Building the Software:
======================

Building U-Boot has been tested in native PPC environments (on a
PowerBook G3 running LinuxPPC 2000) and in cross environments
(running RedHat 6.x and 7.x Linux on x86, Solaris 2.6 on a SPARC, and
NetBSD 1.5 on x86).

If you are not using a native PPC environment, it is assumed that you
have the GNU cross compiling tools available in your path and named
with a prefix of "powerpc-linux-". If this is not the case, (e.g. if
you are using Monta Vista's Hard Hat Linux CDK 1.2) you must change
the definition of CROSS_COMPILE in Makefile. For HHL on a 4xx CPU,
change it to:

CROSS_COMPILE = ppc_4xx-


U-Boot is intended to be simple to build. After installing the
sources you must configure U-Boot for one specific board type. This
is done by typing:

make NAME_config

where "NAME_config" is the name of one of the existing
configurations; see the main Makefile for supported names.

Note: for some board special configuration names may exist; check if
additional information is available from the board vendor; for
instance, the TQM823L systems are available without (standard)
or with LCD support. You can select such additional "features"
when chosing the configuration, i. e.

make TQM823L_config
- will configure for a plain TQM823L, i. e. no LCD support

make TQM823L_LCD_config
- will configure for a TQM823L with U-Boot console on LCD

etc.


Finally, type "make all", and you should get some working U-Boot
images ready for download to / installation on your system:

- "u-boot.bin" is a raw binary image
- "u-boot" is an image in ELF binary format
- "u-boot.srec" is in Motorola S-Record format

By default the build is performed locally and the objects are saved
in the source directory. One of the two methods can be used to change
this behavior and build U-Boot to some external directory:

1. Add O= to the make command line invocations:

make O=/tmp/build distclean
make O=/tmp/build NAME_config
make O=/tmp/build all

2. Set environment variable BUILD_DIR to point to the desired location:

export BUILD_DIR=/tmp/build
make distclean
make NAME_config
make all

Note that the command line "O=" setting overrides the BUILD_DIR environment
variable.


Please be aware that the Makefiles assume you are using GNU make, so
for instance on NetBSD you might need to use "gmake" instead of
native "make".


If the system board that you have is not listed, then you will need
to port U-Boot to your hardware platform. To do this, follow these
steps:

1. Add a new configuration option for your board to the toplevel
"Makefile" and to the "MAKEALL" script, using the existing
entries as examples. Note that here and at many other places
boards and other names are listed in alphabetical sort order. Please
keep this order.
2. Create a new directory to hold your board specific code. Add any
files you need. In your board directory, you will need at least
the "Makefile", a "<board>.c", "flash.c" and "u-boot.lds".
3. Create a new configuration file "include/configs/<board>.h" for
your board
3. If you're porting U-Boot to a new CPU, then also create a new
directory to hold your CPU specific code. Add any files you need.
4. Run "make <board>_config" with your new name.
5. Type "make", and you should get a working "u-boot.srec" file
to be installed on your target system.
6. Debug and solve any problems that might arise.
[Of course, this last step is much harder than it sounds.]


Testing of U-Boot Modifications, Ports to New Hardware, etc.:
==============================================================

If you have modified U-Boot sources (for instance added a new board
or support for new devices, a new CPU, etc.) you are expected to
provide feedback to the other developers. The feedback normally takes
the form of a "patch", i. e. a context diff against a certain (latest
official or latest in CVS) version of U-Boot sources.

But before you submit such a patch, please verify that your modifi-
cation did not break existing code. At least make sure that *ALL* of
the supported boards compile WITHOUT ANY compiler warnings. To do so,
just run the "MAKEALL" script, which will configure and build U-Boot
for ALL supported system. Be warned, this will take a while. You can
select which (cross) compiler to use by passing a `CROSS_COMPILE'
environment variable to the script, i. e. to use the cross tools from
MontaVista's Hard Hat Linux you can type

CROSS_COMPILE=ppc_8xx- MAKEALL

or to build on a native PowerPC system you can type

CROSS_COMPILE=' ' MAKEALL

When using the MAKEALL script, the default behaviour is to build U-Boot
in the source directory. This location can be changed by setting the
BUILD_DIR environment variable. Also, for each target built, the MAKEALL
script saves two log files (<target>.ERR and <target>.MAKEALL) in the
<source dir>/LOG directory. This default location can be changed by
setting the MAKEALL_LOGDIR environment variable. For example:

export BUILD_DIR=/tmp/build
export MAKEALL_LOGDIR=/tmp/log
CROSS_COMPILE=ppc_8xx- MAKEALL

With the above settings build objects are saved in the /tmp/build, log
files are saved in the /tmp/log and the source tree remains clean during
the whole build process.


See also "U-Boot Porting Guide" below.


Monitor Commands - Overview:
============================

go - start application at address 'addr'
run - run commands in an environment variable
bootm - boot application image from memory
bootp - boot image via network using BootP/TFTP protocol
tftpboot- boot image via network using TFTP protocol
and env variables "ipaddr" and "serverip"
(and eventually "gatewayip")
rarpboot- boot image via network using RARP/TFTP protocol
diskboot- boot from IDE devicebootd - boot default, i.e., run 'bootcmd'
loads - load S-Record file over serial line
loadb - load binary file over serial line (kermit mode)
md - memory display
mm - memory modify (auto-incrementing)
nm - memory modify (constant address)
mw - memory write (fill)
cp - memory copy
cmp - memory compare
crc32 - checksum calculation
imd - i2c memory display
imm - i2c memory modify (auto-incrementing)
inm - i2c memory modify (constant address)
imw - i2c memory write (fill)
icrc32 - i2c checksum calculation
iprobe - probe to discover valid I2C chip addresses
iloop - infinite loop on address range
isdram - print SDRAM configuration information
sspi - SPI utility commands
base - print or set address offset
printenv- print environment variables
setenv - set environment variables
saveenv - save environment variables to persistent storage
protect - enable or disable FLASH write protection
erase - erase FLASH memory
flinfo - print FLASH memory information
bdinfo - print Board Info structure
iminfo - print header information for application image
coninfo - print console devices and informations
ide - IDE sub-system
loop - infinite loop on address range
loopw - infinite write loop on address range
mtest - simple RAM test
icache - enable or disable instruction cache
dcache - enable or disable data cache
reset - Perform RESET of the CPU
echo - echo args to console
version - print monitor version
help - print online help
? - alias for 'help'


Monitor Commands - Detailed Description:
========================================

TODO.

For now: just type "help <command>".


Environment Variables:
======================

U-Boot supports user configuration using Environment Variables which
can be made persistent by saving to Flash memory.

Environment Variables are set using "setenv", printed using
"printenv", and saved to Flash using "saveenv". Using "setenv"
without a value can be used to delete a variable from the
environment. As long as you don't save the environment you are
working with an in-memory copy. In case the Flash area containing the
environment is erased by accident, a default environment is provided.

Some configuration options can be set using Environment Variables:

baudrate - see CONFIG_BAUDRATE

bootdelay - see CONFIG_BOOTDELAY

bootcmd - see CONFIG_BOOTCOMMAND

bootargs - Boot arguments when booting an RTOS image

bootfile - Name of the image to load with TFTP

autoload - if set to "no" (any string beginning with 'n'),
"bootp" will just load perform a lookup of the
configuration from the BOOTP server, but not try to
load any image using TFTP

autostart - if set to "yes", an image loaded using the "bootp",
"rarpboot", "tftpboot" or "diskboot" commands will
be automatically started (by internally calling
"bootm")

If set to "no", a standalone image passed to the
"bootm" command will be copied to the load address
(and eventually uncompressed), but NOT be started.
This can be used to load and uncompress arbitrary
data.

i2cfast - (PPC405GP|PPC405EP only)
if set to 'y' configures Linux I2C driver for fast
mode (400kHZ). This environment variable is used in
initialization code. So, for changes to be effective
it must be saved and board must be reset.

initrd_high - restrict positioning of initrd images:
If this variable is not set, initrd images will be
copied to the highest possible address in RAM; this
is usually what you want since it allows for
maximum initrd size. If for some reason you want to
make sure that the initrd image is loaded below the
CFG_BOOTMAPSZ limit, you can set this environment
variable to a value of "no" or "off" or "0".
Alternatively, you can set it to a maximum upper
address to use (U-Boot will still check that it
does not overwrite the U-Boot stack and data).

For instance, when you have a system with 16 MB
RAM, and want to reserve 4 MB from use by Linux,
you can do this by adding "mem=12M" to the value of
the "bootargs" variable. However, now you must make
sure that the initrd image is placed in the first
12 MB as well - this can be done with

setenv initrd_high 00c00000

If you set initrd_high to 0xFFFFFFFF, this is an
indication to U-Boot that all addresses are legal
for the Linux kernel, including addresses in flash
memory. In this case U-Boot will NOT COPY the
ramdisk at all. This may be useful to reduce the
boot time on your system, but requires that this
feature is supported by your Linux kernel.

ipaddr - IP address; needed for tftpboot command

loadaddr - Default load address for commands like "bootp",
"rarpboot", "tftpboot", "loadb" or "diskboot"

loads_echo - see CONFIG_LOADS_ECHO

serverip - TFTP server IP address; needed for tftpboot command

bootretry - see CONFIG_BOOT_RETRY_TIME

bootdelaykey - see CONFIG_AUTOBOOT_DELAY_STR

bootstopkey - see CONFIG_AUTOBOOT_STOP_STR

ethprime - When CONFIG_NET_MULTI is enabled controls which
interface is used first.

ethact - When CONFIG_NET_MULTI is enabled controls which
interface is currently active. For example you
can do the following

=> setenv ethact FEC ETHERNET
=> ping 192.168.0.1 # traffic sent on FEC ETHERNET
=> setenv ethact SCC ETHERNET
=> ping 10.0.0.1 # traffic sent on SCC ETHERNET

ethrotate - When set to "no" U-Boot does not go through all
available network interfaces.
It just stays at the currently selected interface.

netretry - When set to "no" each network operation will
either succeed or fail without retrying.
When set to "once" the network operation will
fail when all the available network interfaces
are tried once without success.
Useful on scripts which control the retry operation
themselves.

npe_ucode - see CONFIG_IXP4XX_NPE_EXT_UCOD
if set load address for the npe microcode

tftpsrcport - If this is set, the value is used for TFTP's
UDP source port.

tftpdstport - If this is set, the value is used for TFTP's UDP
destination port instead of the Well Know Port 69.

vlan - When set to a value < 4095 the traffic over
ethernet is encapsulated/received over 802.1q
VLAN tagged frames.

The following environment variables may be used and automatically
updated by the network boot commands ("bootp" and "rarpboot"),
depending the information provided by your boot server:

bootfile - see above
dnsip - IP address of your Domain Name Server
dnsip2 - IP address of your secondary Domain Name Server
gatewayip - IP address of the Gateway (Router) to use
hostname - Target hostname
ipaddr - see above
netmask - Subnet Mask
rootpath - Pathname of the root filesystem on the NFS server
serverip - see above


There are two special Environment Variables:

serial# - contains hardware identification information such
as type string and/or serial number
ethaddr - Ethernet address

These variables can be set only once (usually during manufacturing of
the board). U-Boot refuses to delete or overwrite these variables
once they have been set once.


Further special Environment Variables:

ver - Contains the U-Boot version string as printed
with the "version" command. This variable is
readonly (see CONFIG_VERSION_VARIABLE).


Please note that changes to some configuration parameters may take
only effect after the next boot (yes, that's just like Windoze :-).


Command Line Parsing:
=====================

There are two different command line parsers available with U-Boot:
the old "simple" one, and the much more powerful "hush" shell:

Old, simple command line parser:
--------------------------------

- supports environment variables (through setenv / saveenv commands)
- several commands on one line, separated by ';'
- variable substitution using "... ${name} ..." syntax
- special characters ('$', ';') can be escaped by prefixing with '\',
for example:
setenv bootcmd bootm \${address}
- You can also escape text by enclosing in single apostrophes, for example:
setenv addip 'setenv bootargs $bootargs ip=$ipaddr:$serverip:$gatewayip:$netmask:$hostname::off'

Hush shell:
-----------

- similar to Bourne shell, with control structures like
if...then...else...fi, for...do...done; while...do...done,
until...do...done, ...
- supports environment ("global") variables (through setenv / saveenv
commands) and local shell variables (through standard shell syntax
"name=value"); only environment variables can be used with "run"
command

General rules:
--------------

(1) If a command line (or an environment variable executed by a "run"
command) contains several commands separated by semicolon, and
one of these commands fails, then the remaining commands will be
executed anyway.

(2) If you execute several variables with one call to run (i. e.
calling run with a list af variables as arguments), any failing
command will cause "run" to terminate, i. e. the remaining
variables are not executed.

Note for Redundant Ethernet Interfaces:
=======================================

Some boards come with redundant ethernet interfaces; U-Boot supports
such configurations and is capable of automatic selection of a
"working" interface when needed. MAC assignment works as follows:

Network interfaces are numbered eth0, eth1, eth2, ... Corresponding
MAC addresses can be stored in the environment as "ethaddr" (=>eth0),
"eth1addr" (=>eth1), "eth2addr", ...

If the network interface stores some valid MAC address (for instance
in SROM), this is used as default address if there is NO correspon-
ding setting in the environment; if the corresponding environment
variable is set, this overrides the settings in the card; that means:

o If the SROM has a valid MAC address, and there is no address in the
environment, the SROM's address is used.

o If there is no valid address in the SROM, and a definition in the
environment exists, then the value from the environment variable is
used.

o If both the SROM and the environment contain a MAC address, and
both addresses are the same, this MAC address is used.

o If both the SROM and the environment contain a MAC address, and the
addresses differ, the value from the environment is used and a
warning is printed.

o If neither SROM nor the environment contain a MAC address, an error
is raised.


Image Formats:
==============

The "boot" commands of this monitor operate on "image" files which
can be basicly anything, preceeded by a special header; see the
definitions in include/image.h for details; basicly, the header
defines the following image properties:

* Target Operating System (Provisions for OpenBSD, NetBSD, FreeBSD,
4.4BSD, Linux, SVR4, Esix, Solaris, Irix, SCO, Dell, NCR, VxWorks,
LynxOS, pSOS, QNX, RTEMS, ARTOS;
Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, ARTOS, LynxOS).
* Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
IA64, MIPS, NIOS, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
Currently supported: ARM, AVR32, Intel x86, MIPS, NIOS, PowerPC).
* Compression Type (uncompressed, gzip, bzip2)
* Load Address
* Entry Point
* Image Name
* Image Timestamp

The header is marked by a special Magic Number, and both the header
and the data portions of the image are secured against corruption by
CRC32 checksums.


Linux Support:
==============

Although U-Boot should support any OS or standalone application
easily, the main focus has always been on Linux during the design of
U-Boot.

U-Boot includes many features that so far have been part of some
special "boot loader" code within the Linux kernel. Also, any
"initrd" images to be used are no longer part of one big Linux image;
instead, kernel and "initrd" are separate images. This implementation
serves several purposes:

- the same features can be used for other OS or standalone
applications (for instance: using compressed images to reduce the
Flash memory footprint)

- it becomes much easier to port new Linux kernel versions because
lots of low-level, hardware dependent stuff are done by U-Boot

- the same Linux kernel image can now be used with different "initrd"
images; of course this also means that different kernel images can
be run with the same "initrd". This makes testing easier (you don't
have to build a new "zImage.initrd" Linux image when you just
change a file in your "initrd"). Also, a field-upgrade of the
software is easier now.


Linux HOWTO:
============

Porting Linux to U-Boot based systems:
---------------------------------------

U-Boot cannot save you from doing all the necessary modifications to
configure the Linux device drivers for use with your target hardware
(no, we don't intend to provide a full virtual machine interface to
Linux :-).

But now you can ignore ALL boot loader code (in arch/ppc/mbxboot).

Just make sure your machine specific header file (for instance
include/asm-ppc/tqm8xx.h) includes the same definition of the Board
Information structure as we define in include/u-boot.h, and make
sure that your definition of IMAP_ADDR uses the same value as your
U-Boot configuration in CFG_IMMR.


Configuring the Linux kernel:
-----------------------------

No specific requirements for U-Boot. Make sure you have some root
device (initial ramdisk, NFS) for your target system.


Building a Linux Image:
-----------------------

With U-Boot, "normal" build targets like "zImage" or "bzImage" are
not used. If you use recent kernel source, a new build target
"uImage" will exist which automatically builds an image usable by
U-Boot. Most older kernels also have support for a "pImage" target,
which was introduced for our predecessor project PPCBoot and uses a
100% compatible format.

Example:

make TQM850L_config
make oldconfig
make dep
make uImage

The "uImage" build target uses a special tool (in 'tools/mkimage') to
encapsulate a compressed Linux kernel image with header information,
CRC32 checksum etc. for use with U-Boot. This is what we are doing:

* build a standard "vmlinux" kernel image (in ELF binary format):

* convert the kernel into a raw binary image:

${CROSS_COMPILE}-objcopy -O binary \
-R .note -R .comment \
-S vmlinux linux.bin

* compress the binary image:

gzip -9 linux.bin

* package compressed binary image for U-Boot:

mkimage -A ppc -O linux -T kernel -C gzip \
-a 0 -e 0 -n "Linux Kernel Image" \
-d linux.bin.gz uImage


The "mkimage" tool can also be used to create ramdisk images for use
with U-Boot, either separated from the Linux kernel image, or
combined into one file. "mkimage" encapsulates the images with a 64
byte header containing information about target architecture,
operating system, image type, compression method, entry points, time
stamp, CRC32 checksums, etc.

"mkimage" can be called in two ways: to verify existing images and
print the header information, or to build new images.

In the first form (with "-l" option) mkimage lists the information
contained in the header of an existing U-Boot image; this includes
checksum verification:

tools/mkimage -l image
-l ==> list image header information

The second form (with "-d" option) is used to build a U-Boot image
from a "data file" which is used as image payload:

tools/mkimage -A arch -O os -T type -C comp -a addr -e ep \
-n name -d data_file image
-A ==> set architecture to 'arch'
-O ==> set operating system to 'os'
-T ==> set image type to 'type'
-C ==> set compression type 'comp'
-a ==> set load address to 'addr' (hex)
-e ==> set entry point to 'ep' (hex)
-n ==> set image name to 'name'
-d ==> use image data from 'datafile'

Right now, all Linux kernels for PowerPC systems use the same load
address (0x00000000), but the entry point address depends on the
kernel version:

- 2.2.x kernels have the entry point at 0x0000000C,
- 2.3.x and later kernels have the entry point at 0x00000000.

So a typical call to build a U-Boot image would read:

-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
> -A ppc -O linux -T kernel -C gzip -a 0 -e 0 \
> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux.gz \
> examples/uImage.TQM850L
Image Name: 2.4.4 kernel for TQM850L
Created: Wed Jul 19 02:34:59 2000
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
Load Address: 0x00000000
Entry Point: 0x00000000

To verify the contents of the image (or check for corruption):

-> tools/mkimage -l examples/uImage.TQM850L
Image Name: 2.4.4 kernel for TQM850L
Created: Wed Jul 19 02:34:59 2000
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 335725 Bytes = 327.86 kB = 0.32 MB
Load Address: 0x00000000
Entry Point: 0x00000000

NOTE: for embedded systems where boot time is critical you can trade
speed for memory and install an UNCOMPRESSED image instead: this
needs more space in Flash, but boots much faster since it does not
need to be uncompressed:

-> gunzip /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux.gz
-> tools/mkimage -n '2.4.4 kernel for TQM850L' \
> -A ppc -O linux -T kernel -C none -a 0 -e 0 \
> -d /opt/elsk/ppc_8xx/usr/src/linux-2.4.4/arch/ppc/coffboot/vmlinux \
> examples/uImage.TQM850L-uncompressed
Image Name: 2.4.4 kernel for TQM850L
Created: Wed Jul 19 02:34:59 2000
Image Type: PowerPC Linux Kernel Image (uncompressed)
Data Size: 792160 Bytes = 773.59 kB = 0.76 MB
Load Address: 0x00000000
Entry Point: 0x00000000


Similar you can build U-Boot images from a 'ramdisk.image.gz' file
when your kernel is intended to use an initial ramdisk:

-> tools/mkimage -n 'Simple Ramdisk Image' \
> -A ppc -O linux -T ramdisk -C gzip \
> -d /LinuxPPC/images/SIMPLE-ramdisk.image.gz examples/simple-initrd
Image Name: Simple Ramdisk Image
Created: Wed Jan 12 14:01:50 2000
Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
Data Size: 566530 Bytes = 553.25 kB = 0.54 MB
Load Address: 0x00000000
Entry Point: 0x00000000


Installing a Linux Image:
-------------------------

To downloading a U-Boot image over the serial (console) interface,
you must convert the image to S-Record format:

objcopy -I binary -O srec examples/image examples/image.srec

The 'objcopy' does not understand the information in the U-Boot
image header, so the resulting S-Record file will be relative to
address 0x00000000. To load it to a given address, you need to
specify the target address as 'offset' parameter with the 'loads'
command.

Example: install the image to address 0x40100000 (which on the
TQM8xxL is in the first Flash bank):

=> erase 40100000 401FFFFF

.......... done
Erased 8 sectors

=> loads 40100000
## Ready for S-Record download ...
~>examples/image.srec
1 2 3 4 5 6 7 8 9 10 11 12 13 ...
...
15989 15990 15991 15992
[file transfer complete]
[connected]
## Start Addr = 0x00000000


You can check the success of the download using the 'iminfo' command;
this includes a checksum verification so you can be sure no data
corruption happened:

=> imi 40100000

## Checking Image at 40100000 ...
Image Name: 2.2.13 for initrd on TQM850L
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 335725 Bytes = 327 kB = 0 MB
Load Address: 00000000
Entry Point: 0000000c
Verifying Checksum ... OK


Boot Linux:
-----------

The "bootm" command is used to boot an application that is stored in
memory (RAM or Flash). In case of a Linux kernel image, the contents
of the "bootargs" environment variable is passed to the kernel as
parameters. You can check and modify this variable using the
"printenv" and "setenv" commands:


=> printenv bootargs
bootargs=root=/dev/ram

=> setenv bootargs root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2

=> printenv bootargs
bootargs=root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2

=> bootm 40020000
## Booting Linux kernel at 40020000 ...
Image Name: 2.2.13 for NFS on TQM850L
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 381681 Bytes = 372 kB = 0 MB
Load Address: 00000000
Entry Point: 0000000c
Verifying Checksum ... OK
Uncompressing Kernel Image ... OK
Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:35:17 MEST 2000
Boot arguments: root=/dev/nfs rw nfsroot=10.0.0.2:/LinuxPPC nfsaddrs=10.0.0.99:10.0.0.2
time_init: decrementer frequency = 187500000/60
Calibrating delay loop... 49.77 BogoMIPS
Memory: 15208k available (700k kernel code, 444k data, 32k init) [c0000000,c1000000]
...

If you want to boot a Linux kernel with initial ram disk, you pass
the memory addresses of both the kernel and the initrd image (PPBCOOT
format!) to the "bootm" command:

=> imi 40100000 40200000

## Checking Image at 40100000 ...
Image Name: 2.2.13 for initrd on TQM850L
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 335725 Bytes = 327 kB = 0 MB
Load Address: 00000000
Entry Point: 0000000c
Verifying Checksum ... OK

## Checking Image at 40200000 ...
Image Name: Simple Ramdisk Image
Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
Data Size: 566530 Bytes = 553 kB = 0 MB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK

=> bootm 40100000 40200000
## Booting Linux kernel at 40100000 ...
Image Name: 2.2.13 for initrd on TQM850L
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 335725 Bytes = 327 kB = 0 MB
Load Address: 00000000
Entry Point: 0000000c
Verifying Checksum ... OK
Uncompressing Kernel Image ... OK
## Loading RAMDisk Image at 40200000 ...
Image Name: Simple Ramdisk Image
Image Type: PowerPC Linux RAMDisk Image (gzip compressed)
Data Size: 566530 Bytes = 553 kB = 0 MB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
Loading Ramdisk ... OK
Linux version 2.2.13 (wd@denx.local.net) (gcc version 2.95.2 19991024 (release)) #1 Wed Jul 19 02:32:08 MEST 2000
Boot arguments: root=/dev/ram
time_init: decrementer frequency = 187500000/60
Calibrating delay loop... 49.77 BogoMIPS
...
RAMDISK: Compressed image found at block 0
VFS: Mounted root (ext2 filesystem).

bash#

Boot Linux and pass a flat device tree:
-----------

First, U-Boot must be compiled with the appropriate defines. See the section
titled "Linux Kernel Interface" above for a more in depth explanation. The
following is an example of how to start a kernel and pass an updated
flat device tree:

=> print oftaddr
oftaddr=0x300000
=> print oft
oft=oftrees/mpc8540ads.dtb
=> tftp $oftaddr $oft
Speed: 1000, full duplex
Using TSEC0 device
TFTP from server 192.168.1.1; our IP address is 192.168.1.101
Filename 'oftrees/mpc8540ads.dtb'.
Load address: 0x300000
Loading: #
done
Bytes transferred = 4106 (100a hex)
=> tftp $loadaddr $bootfile
Speed: 1000, full duplex
Using TSEC0 device
TFTP from server 192.168.1.1; our IP address is 192.168.1.2
Filename 'uImage'.
Load address: 0x200000
Loading:############
done
Bytes transferred = 1029407 (fb51f hex)
=> print loadaddr
loadaddr=200000
=> print oftaddr
oftaddr=0x300000
=> bootm $loadaddr - $oftaddr
## Booting image at 00200000 ...
Image Name: Linux-2.6.17-dirty
Image Type: PowerPC Linux Kernel Image (gzip compressed)
Data Size: 1029343 Bytes = 1005.2 kB
Load Address: 00000000
Entry Point: 00000000
Verifying Checksum ... OK
Uncompressing Kernel Image ... OK
Booting using flat device tree at 0x300000
Using MPC85xx ADS machine description
Memory CAM mapping: CAM0=256Mb, CAM1=256Mb, CAM2=0Mb residual: 0Mb
[snip]


More About U-Boot Image Types:
------------------------------

U-Boot supports the following image types:

"Standalone Programs" are directly runnable in the environment
provided by U-Boot; it is expected that (if they behave
well) you can continue to work in U-Boot after return from
the Standalone Program.
"OS Kernel Images" are usually images of some Embedded OS which
will take over control completely. Usually these programs
will install their own set of exception handlers, device
drivers, set up the MMU, etc. - this means, that you cannot
expect to re-enter U-Boot except by resetting the CPU.
"RAMDisk Images" are more or less just data blocks, and their
parameters (address, size) are passed to an OS kernel that is
being started.
"Multi-File Images" contain several images, typically an OS
(Linux) kernel image and one or more data images like
RAMDisks. This construct is useful for instance when you want
to boot over the network using BOOTP etc., where the boot
server provides just a single image file, but you want to get
for instance an OS kernel and a RAMDisk image.

"Multi-File Images" start with a list of image sizes, each
image size (in bytes) specified by an "uint32_t" in network
byte order. This list is terminated by an "(uint32_t)0".
Immediately after the terminating 0 follow the images, one by
one, all aligned on "uint32_t" boundaries (size rounded up to
a multiple of 4 bytes).

"Firmware Images" are binary images containing firmware (like
U-Boot or FPGA images) which usually will be programmed to
flash memory.

"Script files" are command sequences that will be executed by
U-Boot's command interpreter; this feature is especially
useful when you configure U-Boot to use a real shell (hush)
as command interpreter.


Standalone HOWTO:
=================

One of the features of U-Boot is that you can dynamically load and
run "standalone" applications, which can use some resources of
U-Boot like console I/O functions or interrupt services.

Two simple examples are included with the sources:

"Hello World" Demo:
-------------------

'examples/hello_world.c' contains a small "Hello World" Demo
application; it is automatically compiled when you build U-Boot.
It's configured to run at address 0x00040004, so you can play with it
like that:

=> loads
## Ready for S-Record download ...
~>examples/hello_world.srec
1 2 3 4 5 6 7 8 9 10 11 ...
[file transfer complete]
[connected]
## Start Addr = 0x00040004

=> go 40004 Hello World! This is a test.
## Starting application at 0x00040004 ...
Hello World
argc = 7
argv[0] = "40004"
argv[1] = "Hello"
argv[2] = "World!"
argv[3] = "This"
argv[4] = "is"
argv[5] = "a"
argv[6] = "test."
argv[7] = "<NULL>"
Hit any key to exit ...

## Application terminated, rc = 0x0

Another example, which demonstrates how to register a CPM interrupt
handler with the U-Boot code, can be found in 'examples/timer.c'.
Here, a CPM timer is set up to generate an interrupt every second.
The interrupt service routine is trivial, just printing a '.'
character, but this is just a demo program. The application can be
controlled by the following keys:

? - print current values og the CPM Timer registers
b - enable interrupts and start timer
e - stop timer and disable interrupts
q - quit application

=> loads
## Ready for S-Record download ...
~>examples/timer.srec
1 2 3 4 5 6 7 8 9 10 11 ...
[file transfer complete]
[connected]
## Start Addr = 0x00040004

=> go 40004
## Starting application at 0x00040004 ...
TIMERS=0xfff00980
Using timer 1
tgcr @ 0xfff00980, tmr @ 0xfff00990, trr @ 0xfff00994, tcr @ 0xfff00998, tcn @ 0xfff0099c, ter @ 0xfff009b0

Hit 'b':
[q, b, e, ?] Set interval 1000000 us
Enabling timer
Hit '?':
[q, b, e, ?] ........
tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0xef6, ter=0x0
Hit '?':
[q, b, e, ?] .
tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x2ad4, ter=0x0
Hit '?':
[q, b, e, ?] .
tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x1efc, ter=0x0
Hit '?':
[q, b, e, ?] .
tgcr=0x1, tmr=0xff1c, trr=0x3d09, tcr=0x0, tcn=0x169d, ter=0x0
Hit 'e':
[q, b, e, ?] ...Stopping timer
Hit 'q':
[q, b, e, ?] ## Application terminated, rc = 0x0


Minicom warning:
================

Over time, many people have reported problems when trying to use the
"minicom" terminal emulation program for serial download. I (wd)
consider minicom to be broken, and recommend not to use it. Under
Unix, I recommend to use C-Kermit for general purpose use (and
especially for kermit binary protocol download ("loadb" command), and
use "cu" for S-Record download ("loads" command).

Nevertheless, if you absolutely want to use it try adding this
configuration to your "File transfer protocols" section:

Name Program Name U/D FullScr IO-Red. Multi
X kermit /usr/bin/kermit -i -l %l -s Y U Y N N
Y kermit /usr/bin/kermit -i -l %l -r N D Y N N


NetBSD Notes:
=============

Starting at version 0.9.2, U-Boot supports NetBSD both as host
(build U-Boot) and target system (boots NetBSD/mpc8xx).

Building requires a cross environment; it is known to work on
NetBSD/i386 with the cross-powerpc-netbsd-1.3 package (you will also
need gmake since the Makefiles are not compatible with BSD make).
Note that the cross-powerpc package does not install include files;
attempting to build U-Boot will fail because <machine/ansi.h> is
missing. This file has to be installed and patched manually:

# cd /usr/pkg/cross/powerpc-netbsd/include
# mkdir powerpc
# ln -s powerpc machine
# cp /usr/src/sys/arch/powerpc/include/ansi.h powerpc/ansi.h
# ${EDIT} powerpc/ansi.h ## must remove __va_list, _BSD_VA_LIST

Native builds *don't* work due to incompatibilities between native
and U-Boot include files.

Booting assumes that (the first part of) the image booted is a
stage-2 loader which in turn loads and then invokes the kernel
proper. Loader sources will eventually appear in the NetBSD source
tree (probably in sys/arc/mpc8xx/stand/u-boot_stage2/); in the
meantime, see ftp://ftp.denx.de/pub/u-boot/ppcboot_stage2.tar.gz


Implementation Internals:
=========================

The following is not intended to be a complete description of every
implementation detail. However, it should help to understand the
inner workings of U-Boot and make it easier to port it to custom
hardware.


Initial Stack, Global Data:
---------------------------

The implementation of U-Boot is complicated by the fact that U-Boot
starts running out of ROM (flash memory), usually without access to
system RAM (because the memory controller is not initialized yet).
This means that we don't have writable Data or BSS segments, and BSS
is not initialized as zero. To be able to get a C environment working
at all, we have to allocate at least a minimal stack. Implementation
options for this are defined and restricted by the CPU used: Some CPU
models provide on-chip memory (like the IMMR area on MPC8xx and
MPC826x processors), on others (parts of) the data cache can be
locked as (mis-) used as memory, etc.

Chris Hallinan posted a good summary of these issues to the
u-boot-users mailing list:

Subject: RE: [U-Boot-Users] RE: More On Memory Bank x (nothingness)?
From: "Chris Hallinan" <clh@net1plus.com>
Date: Mon, 10 Feb 2003 16:43:46 -0500 (22:43 MET)
...

Correct me if I'm wrong, folks, but the way I understand it
is this: Using DCACHE as initial RAM for Stack, etc, does not
require any physical RAM backing up the cache. The cleverness
is that the cache is being used as a temporary supply of
necessary storage before the SDRAM controller is setup. It's
beyond the scope of this list to expain the details, but you
can see how this works by studying the cache architecture and
operation in the architecture and processor-specific manuals.

OCM is On Chip Memory, which I believe the 405GP has 4K. It
is another option for the system designer to use as an
initial stack/ram area prior to SDRAM being available. Either
option should work for you. Using CS 4 should be fine if your
board designers haven't used it for something that would
cause you grief during the initial boot! It is frequently not
used.

CFG_INIT_RAM_ADDR should be somewhere that won't interfere
with your processor/board/system design. The default value
you will find in any recent u-boot distribution in
walnut.h should work for you. I'd set it to a value larger
than your SDRAM module. If you have a 64MB SDRAM module, set
it above 400_0000. Just make sure your board has no resources
that are supposed to respond to that address! That code in
start.S has been around a while and should work as is when
you get the config right.

-Chris Hallinan
DS4.COM, Inc.

It is essential to remember this, since it has some impact on the C
code for the initialization procedures:

* Initialized global data (data segment) is read-only. Do not attempt
to write it.

* Do not use any unitialized global data (or implicitely initialized
as zero data - BSS segment) at all - this is undefined, initiali-
zation is performed later (when relocating to RAM).

* Stack space is very limited. Avoid big data buffers or things like
that.

Having only the stack as writable memory limits means we cannot use
normal global data to share information beween the code. But it
turned out that the implementation of U-Boot can be greatly
simplified by making a global data structure (gd_t) available to all
functions. We could pass a pointer to this data as argument to _all_
functions, but this would bloat the code. Instead we use a feature of
the GCC compiler (Global Register Variables) to share the data: we
place a pointer (gd) to the global data into a register which we
reserve for this purpose.

When choosing a register for such a purpose we are restricted by the
relevant (E)ABI specifications for the current architecture, and by
GCC's implementation.

For PowerPC, the following registers have specific use:
R1: stack pointer
R2: reserved for system use
R3-R4: parameter passing and return values
R5-R10: parameter passing
R13: small data area pointer
R30: GOT pointer
R31: frame pointer

(U-Boot also uses R14 as internal GOT pointer.)

==> U-Boot will use R2 to hold a pointer to the global data

Note: on PPC, we could use a static initializer (since the
address of the global data structure is known at compile time),
but it turned out that reserving a register results in somewhat
smaller code - although the code savings are not that big (on
average for all boards 752 bytes for the whole U-Boot image,
624 text + 127 data).

On Blackfin, the normal C ABI (except for P5) is followed as documented here:
http://docs.blackfin.uclinux.org/doku.php?id=application_binary_interface

==> U-Boot will use P5 to hold a pointer to the global data

On ARM, the following registers are used:

R0: function argument word/integer result
R1-R3: function argument word
R9: GOT pointer
R10: stack limit (used only if stack checking if enabled)
R11: argument (frame) pointer
R12: temporary workspace
R13: stack pointer
R14: link register
R15: program counter

==> U-Boot will use R8 to hold a pointer to the global data

NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
or current versions of GCC may "optimize" the code too much.

Memory Management:
------------------

U-Boot runs in system state and uses physical addresses, i.e. the
MMU is not used either for address mapping nor for memory protection.

The available memory is mapped to fixed addresses using the memory
controller. In this process, a contiguous block is formed for each
memory type (Flash, SDRAM, SRAM), even when it consists of several
physical memory banks.

U-Boot is installed in the first 128 kB of the first Flash bank (on
TQM8xxL modules this is the range 0x40000000 ... 0x4001FFFF). After
booting and sizing and initializing DRAM, the code relocates itself
to the upper end of DRAM. Immediately below the U-Boot code some
memory is reserved for use by malloc() [see CFG_MALLOC_LEN
configuration setting]. Below that, a structure with global Board
Info data is placed, followed by the stack (growing downward).

Additionally, some exception handler code is copied to the low 8 kB
of DRAM (0x00000000 ... 0x00001FFF).

So a typical memory configuration with 16 MB of DRAM could look like
this:

0x0000 0000 Exception Vector code
:
0x0000 1FFF
0x0000 2000 Free for Application Use
:
:

:
:
0x00FB FF20 Monitor Stack (Growing downward)
0x00FB FFAC Board Info Data and permanent copy of global data
0x00FC 0000 Malloc Arena
:
0x00FD FFFF
0x00FE 0000 RAM Copy of Monitor Code
... eventually: LCD or video framebuffer
... eventually: pRAM (Protected RAM - unchanged by reset)
0x00FF FFFF [End of RAM]


System Initialization:
----------------------

In the reset configuration, U-Boot starts at the reset entry point
(on most PowerPC systens at address 0x00000100). Because of the reset
configuration for CS0# this is a mirror of the onboard Flash memory.
To be able to re-map memory U-Boot then jumps to its link address.
To be able to implement the initialization code in C, a (small!)
initial stack is set up in the internal Dual Ported RAM (in case CPUs
which provide such a feature like MPC8xx or MPC8260), or in a locked
part of the data cache. After that, U-Boot initializes the CPU core,
the caches and the SIU.

Next, all (potentially) available memory banks are mapped using a
preliminary mapping. For example, we put them on 512 MB boundaries
(multiples of 0x20000000: SDRAM on 0x00000000 and 0x20000000, Flash
on 0x40000000 and 0x60000000, SRAM on 0x80000000). Then UPM A is
programmed for SDRAM access. Using the temporary configuration, a
simple memory test is run that determines the size of the SDRAM
banks.

When there is more than one SDRAM bank, and the banks are of
different size, the largest is mapped first. For equal size, the first
bank (CS2#) is mapped first. The first mapping is always for address
0x00000000, with any additional banks following immediately to create
contiguous memory starting from 0.

Then, the monitor installs itself at the upper end of the SDRAM area
and allocates memory for use by malloc() and for the global Board
Info data; also, the exception vector code is copied to the low RAM
pages, and the final stack is set up.

Only after this relocation will you have a "normal" C environment;
until that you are restricted in several ways, mostly because you are
running from ROM, and because the code will have to be relocated to a
new address in RAM.


U-Boot Porting Guide:
----------------------

[Based on messages by Jerry Van Baren in the U-Boot-Users mailing
list, October 2002]


int main (int argc, char *argv[])
{
sighandler_t no_more_time;

signal (SIGALRM, no_more_time);
alarm (PROJECT_DEADLINE - toSec (3 * WEEK));

if (available_money > available_manpower) {
pay consultant to port U-Boot;
return 0;
}

Download latest U-Boot source;

Subscribe to u-boot-users mailing list;

if (clueless) {
email ("Hi, I am new to U-Boot, how do I get started?");
}

while (learning) {
Read the README file in the top level directory;
Read http://www.denx.de/twiki/bin/view/DULG/Manual ;
Read the source, Luke;
}

if (available_money > toLocalCurrency ($2500)) {
Buy a BDI2000;
} else {
Add a lot of aggravation and time;
}

Create your own board support subdirectory;

Create your own board config file;

while (!running) {
do {
Add / modify source code;
} until (compiles);
Debug;
if (clueless)
email ("Hi, I am having problems...");
}
Send patch file to Wolfgang;

return 0;
}

void no_more_time (int sig)
{
hire_a_guru();
}


Coding Standards:
-----------------

All contributions to U-Boot should conform to the Linux kernel
coding style; see the file "Documentation/CodingStyle" and the script
"scripts/Lindent" in your Linux kernel source directory. In sources
originating from U-Boot a style corresponding to "Lindent -pcs" (adding
spaces before parameters to function calls) is actually used.

Source files originating from a different project (for example the
MTD subsystem) are generally exempt from these guidelines and are not
reformated to ease subsequent migration to newer versions of those
sources.

Please note that U-Boot is implemented in C (and to some small parts in
Assembler); no C++ is used, so please do not use C++ style comments (//)
in your code.

Please also stick to the following formatting rules:
- remove any trailing white space
- use TAB characters for indentation, not spaces
- make sure NOT to use DOS '\r\n' line feeds
- do not add more than 2 empty lines to source files
- do not add trailing empty lines to source files

Submissions which do not conform to the standards may be returned
with a request to reformat the changes.


Submitting Patches:
-------------------

Since the number of patches for U-Boot is growing, we need to
establish some rules. Submissions which do not conform to these rules
may be rejected, even when they contain important and valuable stuff.

Patches shall be sent to the u-boot-users mailing list.

When you send a patch, please include the following information with
it:

* For bug fixes: a description of the bug and how your patch fixes
this bug. Please try to include a way of demonstrating that the
patch actually fixes something.

* For new features: a description of the feature and your
implementation.

* A CHANGELOG entry as plaintext (separate from the patch)

* For major contributions, your entry to the CREDITS file

* When you add support for a new board, don't forget to add this
board to the MAKEALL script, too.

* If your patch adds new configuration options, don't forget to
document these in the README file.

* The patch itself. If you are accessing the CVS repository use "cvs
update; cvs diff -puRN"; else, use "diff -purN OLD NEW". If your
version of diff does not support these options, then get the latest
version of GNU diff.

The current directory when running this command shall be the top
level directory of the U-Boot source tree, or it's parent directory
(i. e. please make sure that your patch includes sufficient
directory information for the affected files).

We accept patches as plain text, MIME attachments or as uuencoded
gzipped text.

* If one logical set of modifications affects or creates several
files, all these changes shall be submitted in a SINGLE patch file.

* Changesets that contain different, unrelated modifications shall be
submitted as SEPARATE patches, one patch per changeset.


Notes:

* Before sending the patch, run the MAKEALL script on your patched
source tree and make sure that no errors or warnings are reported
for any of the boards.

* Keep your modifications to the necessary minimum: A patch
containing several unrelated changes or arbitrary reformats will be
returned with a request to re-formatting / split it.

* If you modify existing code, make sure that your new code does not
add to the memory footprint of the code ;-) Small is beautiful!
When adding new features, these should compile conditionally only
(using #ifdef), and the resulting code with the new feature
disabled must not need more memory than the old code without your
modification.

* Remember that there is a size limit of 40 kB per message on the
u-boot-users mailing list. Compression may help.