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。
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：
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。
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。
