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通过bootloader下载uboot（uboot1.1.2）到sdram中运行，只需要将include/configs/smdk2410.h中的
#define CONFIG_INIT_CRITICAL /* undef for developing */
注释掉就可以了。
编译后下载到RAM中运行
出现如下显示：
U-Boot 1.1.2 (Jan 26 2007 - 15:13:20)
U-Boot code: 33F80000 -> 33F9834C BSS: -> 33F9C420
RAM Configuration:
Bank #0: 30000000 64 MB
Flash: 512 kB
*** Warning - bad CRC, using default environment
In: serial
Out: serial
Err: serial
SMDK2410 #
在学习uboot代码中有以下几点困惑了好久：
1、在start.s中有如下代码：
#ifndef CONFIG_SKIP_RELOCATE_UBOOT
relocate: /* relocate U-Boot to RAM */
adr r0, _start /* r0
ldr r1, _TEXT_BASE /* test if we run from flash or RAM */
cmp r0, r1 /* don't reloc during debug */
beq stack_setup
ldr r2, _armboot_start /*计算代码段的大小*/
ldr r3, _bss_start
sub r2, r3, r2 /* r2
add r2, r0, r2 /* r2
copy_loop:
ldmia r0!,{r3-r10} /* copy from source address [r0] */
stmia r1!,{r3-r10} /* copy to target address [r1] */
cmp r0, r2 /* until source end addreee [r2] */
ble copy_loop
#endif /* CONFIG_SKIP_RELOCATE_UBOOT */
照他的注释此代码的意思是将uboot的代码段copy到sdram，所以当用别的bootloader将此代码下载到
sdram中运行，这段程序应该是不运行的。但当注释掉这段的话 便会出现错误。
错误原因：没有注意到加载域和运行时域的区别，通过已有的bootloader下在到sdram中的uboot是加载域，而正常运行的uboot应该处于运行时域，所以需要上面的程序将uboot变成运行时域。并且开始地址也在以_TEXT_BASE开始的地址
_TEXT_BASE个人认为应该是/board/config.mk文件中的TEXT_BASE = 0x33F80000。
2、下面代码的作用是给bss段清0
clear_bss:
ldr r0, _bss_start /* find start of bss segment */
ldr r1, _bss_end /* stop here */
mov r2, #0x00000000 /* clear */
clbss_l:
str r2,[r0] /* clear loop... */
add r0,r0, #4
cmp r0,r1
ble clbss_l
自己经过分析认为__bss_start和_bss_end应该是在flash中bss段的开始和结束地址，此处清零应该是在sdram中的数据清零呀，很奇怪！？？？？
错误原因：注意__bss_start和_bss_end所在的指令的意思。
3、今天下载了个uboot1.1.6，使用交叉编译器2.95.3编译出现如下错误：
[root@localhost uboot]# make smdk2410_config
Configuring for smdk2410 board...
[root@localhost uboot]# make
for dir in tools examples post post/cpu ; do make -C $dir _depend ; done
make[1]: Entering directory `/home/plant/uboot/tools'
ln -s ../common/environment.c environment.c
ln -s ../lib_generic/crc32.c crc32.c
make[1]: Leaving directory `/home/plant/uboot/tools'
make[1]: Entering directory `/home/plant/uboot/tools'
make[1]: Nothing to be done for `_depend'.
make[1]: Leaving directory `/home/plant/uboot/tools'
make[1]: Entering directory `/home/plant/uboot/examples'
arm-linux-gcc: hello_world.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: stubs.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
make[1]: *** [.depend] Error 1
make[1]: Leaving directory `/home/plant/uboot/examples'
make[1]: Entering directory `/home/plant/uboot/post'
arm-linux-gcc: cache_8xx.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: cache.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: codec.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: cpu.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: dsp.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: ether.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: i2c.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: memory.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: post.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: rtc.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: spr.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: sysmon.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: tests.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: uart.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: usb.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: watchdog.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
make[1]: *** [.depend] Error 1
make[1]: Leaving directory `/home/plant/uboot/post'
make[1]: Entering directory `/home/plant/uboot/post/cpu'
arm-linux-gcc: asm.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: cmp.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: cmpi.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: two.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: twox.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: three.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: threex.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: threei.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: andi.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: srawi.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: rlwnm.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: rlwinm.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: rlwimi.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: store.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: load.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: cr.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: b.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: multi.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: string.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
arm-linux-gcc: complex.o: ?????????
arm-linux-gcc: unrecognized option `-MQ'
make[1]: *** [.depend] Error 1
make[1]: Leaving directory `/home/plant/uboot/post/cpu'
make: *** [depend] Error 2
经过在google上查找发现，是交叉编译器的版本太低的缘故。
所以换了个低版本的uboot省的调起来麻烦呵呵。
最后使用的是uboot1.1.2。
呵呵虽然还没有实现uboot从nand flash启动，但是起码有显示了，增强了点信心。
本文来自ChinaUnix博客，如果查看原文请点：http://blog.chinaunix.net/u/29387/showart_242790.html |
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发表于 2007-02-04 22:43