dm: pmic: max77686: Correct two typos in a comment

[karo-tx-uboot.git] / doc / README.SPL

diff --git a/doc/README.SPL b/doc/README.SPL
index d53ef9c2c2a56fa787ed773f0b852258c5bac59c..3ba313caa8f73feec3fd0664447f99d3a55664af 100644 (file)
--- a/doc/README.SPL
+++ b/doc/README.SPL
@@ -13,37 +13,32 @@ 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 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.
 
-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.
+A config option named CONFIG_SPL_BUILD is enabled by Kconfig for SPL.
 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
+obj-y += board_spl.o
 else
-COBJS-y += board.o
+obj-y += board.o
 endif
 
-COBJS-$(CONFIG_SPL_BUILD) += foo.o
+obj-$(CONFIG_SPL_BUILD) += foo.o
 
 #ifdef CONFIG_SPL_BUILD
        foo();
 #endif
 
 
-The building of SPL images can be with:
+The building of SPL images can be enabled by CONFIG_SPL option in Kconfig.
 
-#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
+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
@@ -59,6 +54,44 @@ 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.