projects / people / ms / u-boot.git / blame
| Commit | Line | Data |
|---|---|---|
| 6a11cf48 DS |
1 | Generic SPL framework |
| 2 | ===================== | |
| 3 | ||
| 4 | Overview | |
| 5 | -------- | |
| 6 | ||
| 7 | To unify all existing implementations for a secondary program loader (SPL) | |
| 8 | and to allow simply adding of new implementations this generic SPL framework | |
| 9 | has been created. With this framework almost all source files for a board | |
| 10 | can be reused. No code duplication or symlinking is necessary anymore. | |
| 11 | ||
| 12 | ||
| 13 | How it works | |
| 14 | ------------ | |
| 15 | ||
| 16 | There is a new directory TOPDIR/spl which contains only a Makefile. | |
| 17 | The object files are built separately for SPL and placed in this directory. | |
| 18 | The final binaries which are generated are u-boot-spl, u-boot-spl.bin and | |
| 19 | u-boot-spl.map. | |
| 20 | ||
| 21 | During the SPL build a variable named CONFIG_SPL_BUILD is exported | |
| 22 | in the make environment and also appended to CPPFLAGS with -DCONFIG_SPL_BUILD. | |
| 23 | Source files can therefore be compiled for SPL with different settings. | |
| 24 | ARM-based boards have previously used the option CONFIG_PRELOADER for it. | |
| 25 | ||
| 26 | For example: | |
| 27 | ||
| 28 | ifeq ($(CONFIG_SPL_BUILD),y) | |
| 29 | COBJS-y += board_spl.o | |
| 30 | else | |
| 31 | COBJS-y += board.o | |
| 32 | endif | |
| 33 | ||
| 34 | COBJS-$(CONFIG_SPL_BUILD) += foo.o | |
| 35 | ||
| 36 | #ifdef CONFIG_SPL_BUILD | |
| 04e5ae79 | 37 | foo(); |
| 6a11cf48 DS |
38 | #endif |
| 39 | ||
| 40 | ||
| 41 | The building of SPL images can be with: | |
| 42 | ||
| 43 | #define CONFIG_SPL | |
| 44 | ||
| 45 | Because SPL images normally have a different text base, one have to be | |
| 46 | configured by defining CONFIG_SPL_TEXT_BASE. The linker script have to be | |
| 47 | defined with CONFIG_SPL_LDSCRIPT. | |
| 48 | ||
| 49 | To support generic U-Boot libraries and drivers in the SPL binary one can | |
| 50 | optionally define CONFIG_SPL_XXX_SUPPORT. Currently following options | |
| 51 | are supported: | |
| 52 | ||
| 53 | CONFIG_SPL_LIBCOMMON_SUPPORT (common/libcommon.o) | |
| 54 | CONFIG_SPL_LIBDISK_SUPPORT (disk/libdisk.o) | |
| 55 | CONFIG_SPL_I2C_SUPPORT (drivers/i2c/libi2c.o) | |
| 56 | CONFIG_SPL_GPIO_SUPPORT (drivers/gpio/libgpio.o) | |
| 57 | CONFIG_SPL_MMC_SUPPORT (drivers/mmc/libmmc.o) | |
| 58 | CONFIG_SPL_SERIAL_SUPPORT (drivers/serial/libserial.o) | |
| 59 | CONFIG_SPL_SPI_FLASH_SUPPORT (drivers/mtd/spi/libspi_flash.o) | |
| 60 | CONFIG_SPL_SPI_SUPPORT (drivers/spi/libspi.o) | |
| 61 | CONFIG_SPL_FAT_SUPPORT (fs/fat/libfat.o) | |
| 62 | CONFIG_SPL_LIBGENERIC_SUPPORT (lib/libgeneric.o) |