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author | Yang Zhang <yang.z.zhang@intel.com> | 2015-08-28 09:58:54 +0800 |
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committer | Yang Zhang <yang.z.zhang@intel.com> | 2015-09-01 12:44:00 +0800 |
commit | e44e3482bdb4d0ebde2d8b41830ac2cdb07948fb (patch) | |
tree | 66b09f592c55df2878107a468a91d21506104d3f /qemu/roms/u-boot/doc/README.SPL | |
parent | 9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (diff) |
Add qemu 2.4.0
Change-Id: Ic99cbad4b61f8b127b7dc74d04576c0bcbaaf4f5
Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
Diffstat (limited to 'qemu/roms/u-boot/doc/README.SPL')
-rw-r--r-- | qemu/roms/u-boot/doc/README.SPL | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/qemu/roms/u-boot/doc/README.SPL b/qemu/roms/u-boot/doc/README.SPL new file mode 100644 index 000000000..57a39a489 --- /dev/null +++ b/qemu/roms/u-boot/doc/README.SPL @@ -0,0 +1,112 @@ +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 $(srctree)/spl which contains only a Makefile. +The object files are built separately for SPL and placed in this directory. +The final binaries which are generated are u-boot-spl, u-boot-spl.bin and +u-boot-spl.map. + +During the SPL build a variable named CONFIG_SPL_BUILD is exported +in the make environment and also appended to CPPFLAGS with -DCONFIG_SPL_BUILD. +Source files can therefore be compiled for SPL with different settings. +ARM-based boards have previously used the option CONFIG_PRELOADER for it. + +For example: + +ifeq ($(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 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) + +Normally CPU is assumed to be the same between the SPL and normal +u-boot build. However it is possible to specify a different CPU for +the SPL build for cases where the SPL is expected to run on a +different CPU model from the main u-boot. This is done by specifying +an SPL CPU in boards.cfg as follows: + + normal_cpu:spl_cpu + +This case CPU will be set to "normal_cpu" during the main u-boot +build and "spl_cpu" during the SPL build. + + +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. |