1Generic SPL framework 2===================== 3 4Overview 5-------- 6 7To unify all existing implementations for a secondary program loader (SPL) 8and to allow simply adding of new implementations this generic SPL framework 9has been created. With this framework almost all source files for a board 10can be reused. No code duplication or symlinking is necessary anymore. 11 12 13How it works 14------------ 15 16There is a new directory TOPDIR/spl which contains only a Makefile. 17The object files are built separately for SPL and placed in this directory. 18The final binaries which are generated are u-boot-spl, u-boot-spl.bin and 19u-boot-spl.map. 20 21During the SPL build a variable named CONFIG_SPL_BUILD is exported 22in the make environment and also appended to CPPFLAGS with -DCONFIG_SPL_BUILD. 23Source files can therefore be compiled for SPL with different settings. 24ARM-based boards have previously used the option CONFIG_PRELOADER for it. 25 26For example: 27 28ifeq ($(CONFIG_SPL_BUILD),y) 29COBJS-y += board_spl.o 30else 31COBJS-y += board.o 32endif 33 34COBJS-$(CONFIG_SPL_BUILD) += foo.o 35 36#ifdef CONFIG_SPL_BUILD 37 foo(); 38#endif 39 40 41The building of SPL images can be with: 42 43#define CONFIG_SPL 44 45Because SPL images normally have a different text base, one have to be 46configured by defining CONFIG_SPL_TEXT_BASE. The linker script have to be 47defined with CONFIG_SPL_LDSCRIPT. 48 49To support generic U-Boot libraries and drivers in the SPL binary one can 50optionally define CONFIG_SPL_XXX_SUPPORT. Currently following options 51are supported: 52 53CONFIG_SPL_LIBCOMMON_SUPPORT (common/libcommon.o) 54CONFIG_SPL_LIBDISK_SUPPORT (disk/libdisk.o) 55CONFIG_SPL_I2C_SUPPORT (drivers/i2c/libi2c.o) 56CONFIG_SPL_GPIO_SUPPORT (drivers/gpio/libgpio.o) 57CONFIG_SPL_MMC_SUPPORT (drivers/mmc/libmmc.o) 58CONFIG_SPL_SERIAL_SUPPORT (drivers/serial/libserial.o) 59CONFIG_SPL_SPI_FLASH_SUPPORT (drivers/mtd/spi/libspi_flash.o) 60CONFIG_SPL_SPI_SUPPORT (drivers/spi/libspi.o) 61CONFIG_SPL_FAT_SUPPORT (fs/fat/libfat.o) 62CONFIG_SPL_LIBGENERIC_SUPPORT (lib/libgeneric.o) 63