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diff --git a/doc/README.nios b/doc/README.nios new file mode 100644 index 0000000..2cee723 --- /dev/null +++ b/doc/README.nios @@ -0,0 +1,196 @@ + + U-Boot for Nios-32 + + Last Update: October 4, 2003 +==================================================================== + +This file contains information regarding U-Boot and the Altera +Nios CPU. For information regarding U-Boot and the Nios Development +Kit, Cyclone Edition (DK-1C20), see doc/README.dk1c20. + +For those interested in contributing ... see HELP WANTED below. + + +1. OVERVIEW +------------ + +U-Boot has been successfully tested on the Nios Cyclone development +board using both the 'safe' and 'standard 32' configurations with +Nios CPU revision 3.08 (CPU_ID = 0x3008). U-Boot can be used with +or without the GERMS monitor. The initial version of U-Boot for the +Cyclone development kit is about 60 Kbyte and will fit in a single +sector of on-board FLASH. Only the Nios 32-bit CPU is supported. + +1.1 GERMS Monitor +------------------ +If GERMS is just not enough, then U-Boot is a great antibiotic. +You will be very pleased with its high degree of configurability +and its rich feature set. + +A few of the most obvious limitations of GERMS are overcome by +using U-Boot (See 'Brain Damage'). Most notably, you can use +minicom or Hyperterminal (duh). + +1.2 Altera Source Code +----------------------- +The Nios port does NOT include ANY sources that Altera has the +copyright. This was a conscious decision ... not an accident. +The Altera license is not clear in terms of distributing Altera +sources (when altera silicon is not involved). This isn't really +a problem as little, if any, of the Altera source contains +features that are not already available in U-Boot. + +The Nios port also does not use the long-winded peripheral +structure definitions from the Nios SDK. + + + +2. CONFIGURATION OPTIONS/SETTINGS +---------------------------------- + +2.1 Nios-specific Options/Settings +----------------------------------- +All configuration options/settings that are specific to Nios begin +with "CONFIG_NIOS_" or "CFG_NIOS_". The following is a list of +currently defined Nios-specific options/parameters. If any options +are related to Standard-32 Nios SDK excalibur.h definitions, the +related definition follows the description). + + +CONFIG_NIOS -- defined for all Nios-32 boards. + +CFG_NIOS_CONSOLE -- the base address of the console UART. + (standard-32: na_uart1_base). + +CFG_NIOS_FIXEDBAUD -- defined if the console UART PTF fixed_baud + parameter is set to '1'. + +CFG_NIOS_MULT_HW -- use full hardware multiply (not yet implemented). + +CFG_NIOS_MULT_MSTEP -- use hardware assisted multiply using the + MSTEP instruction (not yet implemented). + +CFG_NIOS_TMRBASE -- the base address of the timer used to support + xxx_timer routines (e.g. set_timer(), get_timer(), etc.). + (standard-32: na_lo_priority_timer2_base). + +CFG_NIOS_TMRIRQ -- the interrupt request (vector number) assigned to + the timer. (standard-32: na_low_priority_timer2_irq). + +CFG_NIOS_TMRMS -- the period of the timer in milliseconds. + +2.2 Differences in U-Boot Options/Settings +------------------------------------------- +Some 'standard' U-Boot options/settings are treated differently in +the Nios port. These are described below. + +CFG_GBL_DATA_OFFSET -- in the Nios port, this is the offset of the + global data structure in the Nios memory space. More simply, + the address of global data. + + +3. ASSEMBLY CODING +------------------- + +In browsing the assembly source files, you may notice the absence +of the 'magic macros' (e.g. MOVIA, MOVIP, ADDIP etc.). This is +deliberate. The documentation for the magic macros is scant and +it is hard to find ... it does not appear in the Nios programmer's +manual, nor does it appear in the assembler manual. Regardless, +the macros actually do very little to improve readability anyway. + +With this in mind, all assembler modules use only instructions that +appear in the Nios programmer's manual OR are directly supported +by the nios-elf toolchain. For example, the 'dec %rB' instruction +is an alias for 'subi %rB,1' that is supported by the assembler +but does not appear in the programmer's manual. + + +4. BRAIN DAMAGE +---------------- + +This section describes some of the unfortunate and avoidable aspects +of working with the Nios CPU ... and some things you can do to +reduce your pain. + +4.1 GERMS doesn't work with Hyperterminal +------------------------------------------ +GERMS doesn't do CR/LF mapping that is compatible with Hyperterminal +(or minicom) -- geez. Regardless of you opion of Hyperterminal, this +sad design decision is remedied by using U-Boot. + +4.2 cygwin Incompatibility +--------------------------- +The version of cygwin distributed with the nios GNUPro toolchain is +out-of-date and incompatible with the latest cygwin distributions. +In addition, many of the standard utilities are very dated as well. +If you try to download and build the lastest version of grep for +example, you'll quickly realize that a native gcc is not available +(the next topic) which leads to U-Boot build problems (following +topic). + +The solution ... well, you can wait for Altera ... or build as +set of tools for linux. + +4.3 No native gcc +------------------ +I'm not sure how this one slipped through the cracks ... but it is +a real pain. Basically, if you want to build anything for the native +environment -- forget it! A native (cygwin) gcc is not distributed, +and the old version of cygwin makes locating one challenging. + +The solution ... same as above. Just download the gcc source from +Altera and build up a set of cross tools for your favorite linux +distro. + +4.4 Can't build default U-Boot +------------------------------- +By default, when you build U-Boot you will be building some native +tools along with the target elf, bin, and srec files. Without a +native gcc, this (obviously) causes problems. + +For developers using the Altera cygwin tools you can remove the +'tools' directory from SUBDIRS in the top-level Makefile. You will +also have to edit common/Makefile: + +Replace: +environment.o: environment.c ../tools/envcrc + $(CC) $(AFLAGS) -Wa,--no-warn \ + -DENV_CRC=$(shell ../tools/envcrc) \ + -c -o $@ environment.c + +With: +environment.o: environment.c ../tools/envcrc + $(CC) $(AFLAGS) -Wa,--no-warn \ + -DENV_CRC=0 \ + -c -o $@ environment.c + +BTW, thats a 'zero' ... not the letter 'O'. + + +5. HELP WANTED +--------------- + +There are plenty of areas where help is needed. Here's are some ideas +for those interested in contributing: + +-SMC 91C111 support. E.g. add in tftpboot, etc. + +-CompactFlash. Port & test CF/FAT. + +-ASMI support. Use ASMI for environment, etc. + +-Bedbug. Develop bedbug for Nios ... or at least provide a disassemble + command. + +-Add boot support for ucLinux (niosnommu). + +-Implement (don't copy Altera code) the __mulxx routines using the + MSTEP and MUL instructions (e.g. CFG_NIOS_MULT_HW and CFG_NIOS_MULT_MSTEP). + + + +Regards, + +--Scott +<smcnutt@psyent.com> |