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 has to be configured by defining CONFIG_SPL_TEXT_BASE. The linker script has 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) CONFIG_SPL_POWER_SUPPORT (drivers/power/libpower.o) CONFIG_SPL_NAND_SUPPORT (drivers/mtd/nand/libnand.o) CONFIG_SPL_DMA_SUPPORT (drivers/dma/libdma.o) CONFIG_SPL_POST_MEM_SUPPORT (post/drivers/memory.o) CONFIG_SPL_NAND_LOAD (drivers/mtd/nand/nand_spl_load.o) CONFIG_SPL_SPI_LOAD (drivers/mtd/spi/spi_spl_load.o) Normally CPU is assumed to be the same between the SPL and normal u-boot build. However it is possible to specify a different CPU for the SPL build for cases where the SPL is expected to run on a different CPU model from the main u-boot. This is done by specifying an SPL CPU in boards.cfg as follows: normal_cpu:spl_cpu This this case CPU will be set to "normal_cpu" during the main u-boot build and "spl_cpu" during the SPL build.