From 6a11cf48a569d747bcf374a8da88393dc209a347 Mon Sep 17 00:00:00 2001 From: Daniel Schwierzeck Date: Mon, 18 Jul 2011 07:48:07 +0000 Subject: spl: add initial support for a generic SPL framework Signed-off-by: Aneesh V Signed-off-by: Daniel Schwierzeck --- doc/README.SPL | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 62 insertions(+) create mode 100644 doc/README.SPL (limited to 'doc/README.SPL') diff --git a/doc/README.SPL b/doc/README.SPL new file mode 100644 index 0000000..ce8e19f --- /dev/null +++ b/doc/README.SPL @@ -0,0 +1,62 @@ +Generic SPL framework +===================== + +Overview +-------- + +To unify all existing implementations for a secondary program loader (SPL) +and to allow simply adding of new implementations this generic SPL framework +has been created. With this framework almost all source files for a board +can be reused. No code duplication or symlinking is necessary anymore. + + +How it works +------------ + +There is a new directory TOPDIR/spl which contains only a Makefile. +The object files are built separately for SPL and placed in this directory. +The final binaries which are generated are u-boot-spl, u-boot-spl.bin and +u-boot-spl.map. + +During the SPL build a variable named CONFIG_SPL_BUILD is exported +in the make environment and also appended to CPPFLAGS with -DCONFIG_SPL_BUILD. +Source files can therefore be compiled for SPL with different settings. +ARM-based boards have previously used the option CONFIG_PRELOADER for it. + +For example: + +ifeq ($(CONFIG_SPL_BUILD),y) +COBJS-y += board_spl.o +else +COBJS-y += board.o +endif + +COBJS-$(CONFIG_SPL_BUILD) += foo.o + +#ifdef CONFIG_SPL_BUILD + foo(); +#endif + + +The building of SPL images can be with: + +#define CONFIG_SPL + +Because SPL images normally have a different text base, one have to be +configured by defining CONFIG_SPL_TEXT_BASE. The linker script have to be +defined with CONFIG_SPL_LDSCRIPT. + +To support generic U-Boot libraries and drivers in the SPL binary one can +optionally define CONFIG_SPL_XXX_SUPPORT. Currently following options +are supported: + +CONFIG_SPL_LIBCOMMON_SUPPORT (common/libcommon.o) +CONFIG_SPL_LIBDISK_SUPPORT (disk/libdisk.o) +CONFIG_SPL_I2C_SUPPORT (drivers/i2c/libi2c.o) +CONFIG_SPL_GPIO_SUPPORT (drivers/gpio/libgpio.o) +CONFIG_SPL_MMC_SUPPORT (drivers/mmc/libmmc.o) +CONFIG_SPL_SERIAL_SUPPORT (drivers/serial/libserial.o) +CONFIG_SPL_SPI_FLASH_SUPPORT (drivers/mtd/spi/libspi_flash.o) +CONFIG_SPL_SPI_SUPPORT (drivers/spi/libspi.o) +CONFIG_SPL_FAT_SUPPORT (fs/fat/libfat.o) +CONFIG_SPL_LIBGENERIC_SUPPORT (lib/libgeneric.o) -- cgit v1.1