| 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 |
| ------------ |
| |
| The object files for SPL are built separately and placed in the "spl" directory. |
| The final binaries which are generated are u-boot-spl, u-boot-spl.bin and |
| u-boot-spl.map. |
| |
| A config option named CONFIG_SPL_BUILD is enabled by Kconfig for SPL. |
| Source files can therefore be compiled for SPL with different settings. |
| |
| For example: |
| |
| ifeq ($(CONFIG_SPL_BUILD),y) |
| obj-y += board_spl.o |
| else |
| obj-y += board.o |
| endif |
| |
| obj-$(CONFIG_SPL_BUILD) += foo.o |
| |
| #ifdef CONFIG_SPL_BUILD |
| foo(); |
| #endif |
| |
| |
| The building of SPL images can be enabled by CONFIG_SPL option in Kconfig. |
| |
| 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_DRIVERS_MISC_SUPPORT (drivers/misc) |
| 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) |
| CONFIG_SPL_RAM_DEVICE (common/spl/spl.c) |
| CONFIG_SPL_WATCHDOG_SUPPORT (drivers/watchdog/libwatchdog.o) |
| |
| |
| Debugging |
| --------- |
| |
| When building SPL with DEBUG set you may also need to set CONFIG_PANIC_HANG |
| as in most cases do_reset is not defined within SPL. |
| |
| |
| Estimating stack usage |
| ---------------------- |
| |
| With gcc 4.6 (and later) and the use of GNU cflow it is possible to estimate |
| stack usage at various points in run sequence of SPL. The -fstack-usage option |
| to gcc will produce '.su' files (such as arch/arm/cpu/armv7/syslib.su) that |
| will give stack usage information and cflow can construct program flow. |
| |
| Must have gcc 4.6 or later, which supports -fstack-usage |
| |
| 1) Build normally |
| 2) Perform the following shell command to generate a list of C files used in |
| SPL: |
| $ find spl -name '*.su' | sed -e 's:^spl/::' -e 's:[.]su$:.c:' > used-spl.list |
| 3) Execute cflow: |
| $ cflow --main=board_init_r `cat used-spl.list` 2>&1 | $PAGER |
| |
| cflow will spit out a number of warnings as it does not parse |
| the config files and picks functions based on #ifdef. Parsing the '.i' |
| files instead introduces another set of headaches. These warnings are |
| not usually important to understanding the flow, however. |