基于nuvoton970学习 uboo2013 之 配置过程
一、介绍
nuvoton 970, 使用的配置为include/configs/nuc970_evb.h。start.S在arch/arm/cpu/arm926ejs/start.S。因为配置文件中使用了CONFIG_NAND_U_BOOT选项，所以会编译出两个目标。
1：u-boot-spl.bin。2：u-boot.bin。
u-boot-spl.bin引导u-boot.bin。
u-boot.bin引导linux。
每一款芯片都会有一段内部固化的程序，叫做BootRom，这段程序是我们不可修改的。芯片一上电Power On，便会启动BootRom。有的芯片内部BootRom负责把第二阶段的Bootloader加载到SRAM中，有的会初始化外部RAM，直接把bootloader加载到外部RAM中运行。而nuc970内的BootRom则是把外部bootloader加载到片内SRAM中运行，一般片内SRAM都会比较小，不能够加载运行一个完整的u-boot，所以u-boot就有了spl机制，spl即 Secondary Program Loader, BootRom为第一阶段， spl就是第二阶段了。u-boot-spl负责初始化外部RAM,并把u-boot主体加载到外部RAM中运行，u-boot主体再去引导kernel。
二、编译和源码分析
我打算按 1、配置阶段为：配置命令–>配置的详细过程
2、u-boot-spl.bin的编译过程
3、u-boot.bin的编译过程
三个阶段开始分析解读：
1、配置命令和配置的详细过程分析
配置命令：
make nuc970_config
在Makefile中能看到：
nuc970_nand_config \
nuc970_config: unconfig
@mkdir -p $(obj)include $(obj)board/nuvoton/nuc970evb
@mkdir -p $(obj)nand_spl/board/nuvoton/nuc970evb
@echo "#define CONFIG_NAND_U_BOOT" > $(obj)include/config.h
@echo "CONFIG_NAND_U_BOOT = y" >> $(obj)include/config.mk
@echo "RAM_TEXT = 0xE00000" >> $(obj)board/nuvoton/nuc970evb/config.tmp
@$(MKCONFIG) nuc970_evb arm arm926ejs nuc970evb nuvoton nuc970首先从这里看出，nuvoton 的配置并没有按照 2013版本的配置去写，这个在后面mkconfig中也有体现，标准被配的写法文章添加。
mkdir -p 的含义：创建指定路径，如果路径存在也不会报错，如果路径的父路径不存在也会创建父路径。所以上面两个创建路径的目的就是保证指定的路径是存在的。接下来三个echo 语句，是往指定文件里面写入内容，重点是最后一句:
@$(MKCONFIG) nuc970_evb arm arm926ejs nuc970evb nuvoton nuc970
查找Makefile 可知$(MKCONFIG)的值为：
MKCONFIG := $(SRCTREE)/mkconfig即当前路径下的 mkconfig 文件，所以配置命令可写成:
mkconfig nuc970_evb arm arm926ejs nuc970evb nuvoton nuc970。
hp:~$ file mkconfig
mkconfig: POSIX shell script, ASCII text executable
查看文件属性，为shell脚本，贴出mkconfig内容：
#!/bin/sh -e
APPEND=no # Default: Create new config file
BOARD_NAME="" # Name to print in make output
TARGETS=""
arch=""
cpu=""
board=""
vendor=""
soc=""
options=""
# 上面定义一些变量赋值为空
##############################################################
##############################################################
# $# 是传入的参数的个数， $1 是传入的第一个参数
if [ \( $# -eq 2 \) -a \( "$1" = "-A" \) ] ; then
# Automatic mode
line=`egrep -i "^[[:space:]]*${2}[[:space:]]" boards.cfg` || {
echo "make: *** No rule to make target \`$2_config'. Stop." >&2
exit 1
}
set ${line}
# add default board name if needed
[ $# = 3 ] && set ${line} ${1}
elif [ "${MAKEFLAGS+set}${MAKELEVEL+set}" = "setset" ] ; then
# only warn when using a config target in the Makefile
cat <<-EOF
warning: Please migrate to boards.cfg. Failure to do so will
mean removal of your board in the next release.
EOF
sleep 5
fi
# 上面if的两种情况，对应配置的两种情况，一种是上面nvoton使用的，就是elif的情况，
# warnning提示下个版本的uboot的配置就不支持这种配置方式了
#######################################################
while [ $# -gt 0 ] ; do
case "$1" in
--) shift ; break ;;
-a) shift ; APPEND=yes ;;
-n) shift ; BOARD_NAME="${1%_config}" ; shift ;;
-t) shift ; TARGETS="`echo $1 | sed 's:_: :g'` ${TARGETS}" ; shift ;;
*) break ;;
esac
done
# 判断第一个参数，nuvoton传入的第一个参数 nuc970_evb
# 所以上面的while 走 *）出来。
#
#
# 检查参数的个数要 大于等于7 小于等于7
[ $# -lt 4 ] && exit 1
[ $# -gt 7 ] && exit 1
# Strip all options and/or _config suffixes
CONFIG_NAME=" ${1%_config}"
# $1 = nuc970_evb 所以 CONFIG_NAME="nuc970_evb_config"
# BOARD_NAME="nuc970_evb_config"
[ "${BOARD_NAME}" ] || BOARD_NAME="${1%_config}"
# $2=arm $3=arm926ejs $4=nuc970evb
# 所以 arch=arm , cpu=arm926ejs board=nuc970evb
arch="$2"
cpu=`echo $3 | awk 'BEGIN {FS = ":"} ; {print $1}'`
spl_cpu=`echo $3 | awk 'BEGIN {FS = ":"} ; {print $2}'`
if [ "$4" = "-" ] ; then
board=${BOARD_NAME}
else
board="$4"
fi
# $5=nuvoton $6=nuc970
# 所以 vendor=nuvoton soc=nuv970
#
[ $# -gt 4 ] && [ "$5" != "-" ] && vendor="$5"
[ $# -gt 5 ] && [ "$6" != "-" ] && soc="$6"
# 传入参数为6 所以下方{}语句不执行
[ $# -gt 6 ] && [ "$7" != "-" ] && {
# check if we have a board config name in the options field
# the options field mave have a board config name and a list
# of options, both separated by a colon (':'); the options are
# separated by commas (',').
#
# Check for board name
tmp="${7%:*}"
if [ "$tmp" ] ; then
CONFIG_NAME="$tmp"
fi
# Check if we only have a colon...
if [ "${tmp}" != "$7" ] ; then
options=${7#*:}
TARGETS="`echo ${options} | sed 's:,: :g'` ${TARGETS}"
fi
}
# -a 这里是条件与的意思 如果 $(ARCH)不为空 并且 $(ARCH) 不等于 $(arch)的话会执行报错语句
#
if [ "${ARCH}" -a "${ARCH}" != "${arch}" ]; then
echo "Failed: \$ARCH=${ARCH}, should be '${arch}' for ${BOARD_NAME}" 1>&2
exit 1
fi
# $options为空，所以走 else
if [ "$options" ] ; then
echo "Configuring for ${BOARD_NAME} - Board: ${CONFIG_NAME}, Options: ${options}"
else
echo "Configuring for ${BOARD_NAME} board..."
fi
#
# Create link to architecture specific headers
# 编译目标路径和源码路径不一致走第一分支，一样的话走 else
# 这里要 include 下创建一些路径和软连接
if [ "$SRCTREE" != "$OBJTREE" ] ; then
mkdir -p ${OBJTREE}/include
mkdir -p ${OBJTREE}/include2
cd ${OBJTREE}/include2
rm -f asm
ln -s ${SRCTREE}/arch/${arch}/include/asm asm
LNPREFIX=${SRCTREE}/arch/${arch}/include/asm/
cd ../include
mkdir -p asm
else
cd ./include
rm -f asm
ln -s ../arch/${arch}/include/asm asm
# 删除include 下的 asm， 建立一个软连接
# include/asm --> arch/arm/include/asm
fi
# 删除include 下的 asm/arch
rm -f asm/arch
# 根据soc的值，soc=nuv970,
# 把asm/arch链接到对应的路径， include/asm/arch ---> include/asm/arch-nuv970
if [ -z "${soc}" ] ; then
ln -s ${LNPREFIX}arch-${cpu} asm/arch
else
ln -s ${LNPREFIX}arch-${soc} asm/arch
fi
#
# 创建一个链接 include/asm/proc ----> include/asm/proc-armv
if [ "${arch}" = "arm" ] ; then
rm -f asm/proc
ln -s ${LNPREFIX}proc-armv asm/proc
fi
#
# Create include file for Make
#
( echo "ARCH = ${arch}"
if [ ! -z "$spl_cpu" ] ; then
echo 'ifeq ($(CONFIG_SPL_BUILD),y)'
echo "CPU = ${spl_cpu}"
echo "else"
echo "CPU = ${cpu}"
echo "endif"
else
echo "CPU = ${cpu}"
fi
echo "BOARD = ${board}"
[ "${vendor}" ] && echo "VENDOR = ${vendor}"
[ "${soc}" ] && echo "SOC = ${soc}"
exit 0 ) > config.mk
# 写入include/config.mk
#
# Assign board directory to BOARDIR variable
if [ -z "${vendor}" ] ; then
BOARDDIR=${board}
else
BOARDDIR=${vendor}/${board}
fi
#
# Create board specific header file
#
if [ "$APPEND" = "yes" ] # Append to existing config file
then
echo >> config.h
else
> config.h # Create new config file
fi
##############################################################################
#
# 创建 include/config.h 配置文件，并写入内容
echo "/* Automatically generated - do not edit */" >>config.h
for i in ${TARGETS} ; do
i="`echo ${i} | sed '/=/ {s/=/ /;q; } ; { s/$/ 1/; }'`"
echo "#define CONFIG_${i}" >>config.h ;
done
echo "#define CONFIG_SYS_ARCH \"${arch}\"" >> config.h
echo "#define CONFIG_SYS_CPU \"${cpu}\"" >> config.h
echo "#define CONFIG_SYS_BOARD \"${board}\"" >> config.h
[ "${vendor}" ] && echo "#define CONFIG_SYS_VENDOR \"${vendor}\"" >> config.h
[ "${soc}" ] && echo "#define CONFIG_SYS_SOC \"${soc}\"" >> config.h
cat << EOF >> config.h
#define CONFIG_BOARDDIR board/$BOARDDIR
#include <config_cmd_defaults.h>
#include <config_defaults.h>
#include <configs/${CONFIG_NAME}.h>
#include <asm/config.h>
#include <config_fallbacks.h>
#include <config_uncmd_spl.h>
EOF
exit 0总结配置过程就是，把对应的头文件路径通过建立软链接联系起来，创建include/config.h和include/config.mk文件给make使用。
tips:
Makefile中有一段配置命令如下：
unconfig:
@rm -f $(obj)include/config.h $(obj)include/config.mk \
$(obj)board/*/config.tmp $(obj)board/*/*/config.tmp \
$(obj)include/autoconf.mk $(obj)include/autoconf.mk.dep
%_config: unconfig
@$(MKCONFIG) -A $(@:_config=)
# $(@:_config=) 就是获取参数的前半部分，就是去掉_config
#配置命令呢，boards.cfg中查找。
例如：
socfpga_cyclone5 arm armv7 socfpga altera socfpga执行配置就是：make socfpga_cyclone5_config
if [ \( $# -eq 2 \) -a \( "$1" = "-A" \) ] ; then
# Automatic mode
line=`egrep -i "^[[:space:]]*${2}[[:space:]]" boards.cfg` || {
echo "make: *** No rule to make target \`$2_config'. Stop." >&2
exit 1
}
#
# 根据配置命令去 boards.cfg 文件中查找对应的配置，
# line= " socfpga_cyclone5 arm armv7 socfpga altera socfpga"
#
set ${line}
# 设置参数: $1 $2 $3 .......
#
#
# add default board name if needed
[ $# = 3 ] && set ${line} ${1}
else
....
fi个人感觉u-boot 2013版本更像是中间过渡版本，后面版本添加个人配置更灵活。
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