| 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) |
| CONFIG_SPL_NAND_SUPPORT (drivers/mtd/nand/libnand.o) |