| 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_EXT_SUPPORT | |
| 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. |