u-boot配置过程分析（ARM）

1.u-boot源码结构

源码目录下一般包含以下目录：

(1) 平台相关的或者开发板相关的，比如cpu/、baord/

(2) 通用的函数，比如common/

(3)通用的设备驱动，比如drivers/

(4)u-boot工具、示例程序、文档，比如/tools/、/examples、/doc

2.u-boot生成配置文件过程

根据顶层readme，如果使用board/板名，必须先执行 make 板名_config，然后执行make all

在Makefile里面有下面

smdk2410_config	:	unconfig
@$(MKCONFIG) $(@:_config=) arm arm920t smdk2410 NULL s3c24x0

而MKCONFIG如下

OBJTREE		:= $(if $(BUILD_DIR),$(BUILD_DIR),$(CURDIR))
SRCTREE		:= $(CURDIR)
TOPDIR		:= $(SRCTREE)
LNDIR		:= $(OBJTREE)
export	TOPDIR SRCTREE OBJTREE

MKCONFIG	:= $(SRCTREE)/mkconfig
export MKCONFIG

转换后就是./mkconfig smdk2410 arm arm920t smdk2410 NULL s3c24x0

下面着重分析这个mkconfig

(1)确定开发板名称

APPEND=no	# Default: Create new config file
BOARD_NAME=""	# Name to print in make output

while [ $# -gt 0 ] ; do
case "$1" in
--) shift ; break ;;
-a) shift ; APPEND=yes ;;
-n) shift ; BOARD_NAME="${1%%_config}" ; shift ;;
*)  break ;;
esac
done

[ "${BOARD_NAME}" ] || BOARD_NAME="$1"

主要判定有没有后缀符-a、--、-n等，默认没有使用，所以结果为BOARD_NAME = smdk2410

(2)创建平台/开发板相关的头文件的链接，(包括asm_arm，asm_arm/arch，asm_arm/proc) 如下代码所示

#
# Create link to architecture specific headers
#
if [ "$SRCTREE" != "$OBJTREE" ] ; then
mkdir -p ${OBJTREE}/include
mkdir -p ${OBJTREE}/include2
cd ${OBJTREE}/include2
rm -f asm
ln -s ${SRCTREE}/include/asm-$2 asm
LNPREFIX="../../include2/asm/"
cd ../include
rm -rf asm-$2
rm -f asm
mkdir asm-$2
ln -s asm-$2 asm
else
cd ./include
rm -f asm
ln -s asm-$2 asm
fi

rm -f asm-$2/arch

if [ -z "$6" -o "$6" = "NULL" ] ; then
ln -s ${LNPREFIX}arch-$3 asm-$2/arch
else
ln -s ${LNPREFIX}arch-$6 asm-$2/arch
fi

if [ "$2" = "arm" ] ; then
rm -f asm-$2/proc
ln -s ${LNPREFIX}proc-armv asm-$2/proc
fi

这里主要是删除之前的链接，然后进行重新链接，主要考虑不同平台下配置不一样

(3)创建include/config.mk

#
# Create include file for Make
#
echo "ARCH   = $2" >  config.mk
echo "CPU    = $3" >> config.mk
echo "BOARD  = $4" >> config.mk

[ "$5" ] && [ "$5" != "NULL" ] && echo "VENDOR = $5" >> config.mk

[ "$6" ] && [ "$6" != "NULL" ] && echo "SOC    = $6" >> config.mk

将ARCH、CPU、BOARD、VENDER、SOC，这里$5=NULL，所以只输出了四项

如下配置mini2440生成的结果

ARCH   = arm
CPU    = arm920t
BOARD  = mini2440
SOC    = s3c24x0

(4)创建开发板相关的头文件 include/config.h

#
# 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
echo "/* Automatically generated - do not edit */" >>config.h
echo "#include <configs/$1.h>" >>config.h

这里APPEND=no，请看（1）处

比如mini2440生成的文件为

/* Automatically generated - do not edit */
#include <configs/mini2440.h>

从以上可以知道，移植时候可以在board目录新建一个开发板的目录，如board/mini2440/

然后会自动生成头文件，上面的include/config.h

另外还需要做一些配置，主要在include/configs/板名.h，比如smdk2410.h

包括两类宏的开启可以启用有关的配置

（1）选项 前缀为CONFIG_ 他们用于选择CPU、SOC、开发板类型、设置系统时钟、选择设备驱动、......

/*
* High Level Configuration Options
* (easy to change)
*/
#define CONFIG_ARM920T		1	/* This is an ARM920T Core	*/
#define	CONFIG_S3C2410		1	/* in a SAMSUNG S3C2410 SoC     */
#define CONFIG_SMDK2410		1	/* on a SAMSUNG SMDK2410 Board  */

/* input clock of PLL */
#define CONFIG_SYS_CLK_FREQ	12000000/* the SMDK2410 has 12MHz input clock */

#define USE_920T_MMU		1
#undef CONFIG_USE_IRQ			/* we don't need IRQ/FIQ stuff */

设置命令、波特率、......

/*
* Command line configuration.
*/
#include <config_cmd_default.h>

#define CONFIG_CMD_CACHE
#define CONFIG_CMD_DATE
#define CONFIG_CMD_ELF

#define CONFIG_BOOTDELAY	3
/*#define CONFIG_BOOTARGS	"root=ramfs devfs=mount console=ttySA0,9600" */
/*#define CONFIG_ETHADDR	08:00:3e:26:0a:5b */
#define CONFIG_NETMASK          255.255.255.0
#define CONFIG_IPADDR		10.0.0.110
#define CONFIG_SERVERIP		10.0.0.1
/*#define CONFIG_BOOTFILE	"elinos-lart" */
/*#define CONFIG_BOOTCOMMAND	"tftp; bootm" */

#if defined(CONFIG_CMD_KGDB)
#define CONFIG_KGDB_BAUDRATE	115200		/* speed to run kgdb serial port */
/* what's this ? it's not used anywhere */
#define CONFIG_KGDB_SER_INDEX	1		/* which serial port to use */
#endif

注意命令中有个config_cmd_default.h 里面包含了默认的uboot命令，可以在里面增加或者删除，也可以在其下面定义有关命令

下面主要是配置启动，网络参数

(2)参数 前缀为CFG_，用于设置malloc缓冲池的大小、uboot提示符、uboot下载默认加载地址、flash起始地址、......

/*
* Size of malloc() pool
*/
#define CFG_MALLOC_LEN		(CONFIG_ENV_SIZE + 128*1024)
#define CFG_GBL_DATA_SIZE	128	/* size in bytes reserved for initial data */

/*
* Hardware drivers
*/
#define CONFIG_DRIVER_CS8900	1	/* we have a CS8900 on-board */
#define CS8900_BASE		0x19000300
#define CS8900_BUS16		1 /* the Linux driver does accesses as shorts */

命令提示符、字符缓冲区的大小、默认下载地址、.......

/*
* Miscellaneous configurable options
*/
#define	CFG_LONGHELP				/* undef to save memory		*/
#define	CFG_PROMPT		"SMDK2410 # "	/* Monitor Command Prompt	*/
#define	CFG_CBSIZE		256		/* Console I/O Buffer Size	*/
#define	CFG_PBSIZE (CFG_CBSIZE+sizeof(CFG_PROMPT)+16) /* Print Buffer Size */
#define	CFG_MAXARGS		16		/* max number of command args	*/
#define CFG_BARGSIZE		CFG_CBSIZE	/* Boot Argument Buffer Size	*/

#define CFG_MEMTEST_START	0x30000000	/* memtest works on	*/
#define CFG_MEMTEST_END		0x33F00000	/* 63 MB in DRAM	*/

#undef  CFG_CLKS_IN_HZ		/* everything, incl board info, in Hz */

#define	CFG_LOAD_ADDR		0x33000000	/* default load address	*/

里面还有stack、物理内存映射、Nor Flash设置、BOOTP设置、.......

3.总结开发板配置过程：

开发板名称->头文件链接->include/config.mk->include/config.h

文档：

#!/bin/sh -e

# Script to create header files and links to configure
# U-Boot for a specific board.
#
# Parameters:  Target  Architecture  CPU  Board [VENDOR] [SOC]
#
# (C) 2002-2006 DENX Software Engineering, Wolfgang Denk <wd@denx.de>
#
#./mkconfig smdk2410 arm arm920t smdk2410 NULL s3c24x0
$0         $1     $2   $3       $4      $5    $6
APPEND=no	      # Default: Create new config file
BOARD_NAME=""	  # Name to print in make output

[ "${BOARD_NAME}" ] || BOARD_NAME="$1"
#BOARD_NAME= smdk2410

[ $# -lt 4 ] && exit 1
[ $# -gt 6 ] && exit 1

echo "Configuring for ${BOARD_NAME} board..."

#
# Create link to architecture specific headers
#

cd ./include
rm -f asm
ln -s asm-$2 asm  # 建立链接文件 ln -s asm-arm asm

rm -f asm-$2/arch   # asm-arm/arch

ln -s ${LNPREFIX}arch-$6 asm-$2/arch  # ln -s arch-s3c24x0 asm-arm/arch

if [ "$2" = "arm" ] ; then
rm -f asm-$2/proc
ln -s ${LNPREFIX}proc-armv asm-$2/proc # ln -s proc-armv asm-arm/proc
fi

#
# Create include file for Make
#
echo "ARCH   = $2" >  config.mk
echo "CPU    = $3" >> config.mk
echo "BOARD  = $4" >> config.mk

#ARCH  = arm
#CPU   = arm920t
#BOARD = smdk2410

[ "$5" ] && [ "$5" != "NULL" ] && echo "VENDOR = $5" >> config.mk

[ "$6" ] && [ "$6" != "NULL" ] && echo "SOC    = $6" >> config.mk
#SOC   = s3c24x0

#
# Create board specific header file
#

> config.h		# Create new config file

echo "/* Automatically generated - do not edit */" >>config.h
echo "#include <configs/$1.h>" >>config.h

#/* Automatically generated - do not edit */
##include <configs/smdk2410.h>

exit 0