记录下启动log
Texas Instruments X-Loader 1.42 BSP-dm37x-2.4-2 for dm3730logic (2013-06-18 15:59:36) DRAM: 256MB (MT29C4G48MAZAPAKQ5) Starting U-boot on MMC Reading boot sector 454540 bytes read from MMC to 80400000 U-Boot 2011.06 BSP-dm37x-2.4-2 (Jun 18 2013 - 15:35:26) OMAP3630/3730-GP ES2.1, CPU-OPP2, L3-200MHz, Max CPU Clock 1 Ghz Logic DM37x/OMAP35x reference board + LPDDR/NAND I2C: ready DRAM: 256 MiB Board: DM37xx SOM LV NOR: no flash device detected NAND: 512 MiB NAND: Internal to NAND ECC selected *** Warning - bad CRC or ECC error, using default environment Found '28' display panel In: serial Out: serial Err: serial Product ID data cached to: 40200000 at88_send_packet:82 NACK idx 3 at88_send_packet:82 NACK idx 3 at88_send_packet:82 NACK idx 3 at88_send_packet:82 NACK idx 3 at88_send_packet:82 NACK idx 3 at88_send_packet:82 NACK idx 3 Die ID #74ae00229ff84000013c124c1700c017 OTG_SYSCONFIG: 00001008 - needs to be 00002001 ID data ROM : Gen 1 Part Number : L3-5000518 Model Name : SOMDM3730-PHI02-0301R-A Serial Number: 2520M01457 LAN ethaddr : 00:08:ee:10:92:ad Data (writethrough) Cache is ON Net: smc911x-0 =================================== NOTICE =================================== The U-Boot environment was not found. If the display is not set properly linux will not have video support. Valid display options are: 2 == LQ121S1DG31 TFT SVGA (12.1) Sharp 3 == LQ036Q1DA01 TFT QVGA (3.6) Sharp w/ASIC 5 == LQ064D343 TFT VGA (6.4) Sharp 7 == LQ10D368 TFT VGA (10.4) Sharp 15 == LQ043T1DG01 TFT WQVGA (4.3) Sharp 28 == LQ043T1DG28 TFT WQVGA (4.3) Sharp (DEFAULT) vga[-16 OR -24] LCD VGA 640x480 svga[-16 OR -24] LCD SVGA 800x600 xga[-16 OR -24] LCD XGA 1024x768 720p[-16 OR -24] LCD 720P 1280x720 sxga[-16 OR -24] LCD SXGA 1280x1024 uxga[-16 OR -24] LCD UXGA 1600x1200 Default `display` environment variable is now being set to: 28 At the U-Boot prompt type commands: `setenv display`, then type `saveenv` to save the environment to NAND flash. This will avoid seeing this notice on future boots =================================== NOTICE =================================== Hit any key to stop autoboot: 3 2 1 0 == Checking mmc1 for alternate boot script boot.scr == mmc1 is available reading boot.scr 129 bytes read == Found script on mmc 1, starting == ## Executing script at 80ff0000 ## Resetting to default environment kernel_location: mmc , rootfs_location: mmc , rootfs_type: ramdisk == Loading kernel file uImage to 0x81000000 == mmc1 is available reading uImage 3977032 bytes read == Loading rootfs file rootfs.ext2.gz.uboot to 0x82000000 == reading rootfs.ext2.gz.uboot 28842095 bytes read == Kernel bootargs == nand-ecc=chip console=ttyO0,115200n8 display=28 ignore_loglevel early_printk no_console_suspend mtdparts=omap2-nand.0:512k(x-loader),1664k(u-boot),384k(u-boot-env),5m(kernel),20m(ramdisk),-(fs) root=/dev/ram rw ramdisk_size=128000 bootm 0x81000000 0x82000000 ## Booting kernel from Legacy Image at 81000000 ... Image Name: Linux-3.0.0-BSP-dm37x-2.4-2 Image Type: ARM Linux Kernel Image (uncompressed) Data Size: 3976968 Bytes = 3.8 MiB Load Address: 80008000 Entry Point: 80008000 Verifying Checksum ... OK ## Loading init Ramdisk from Legacy Image at 82000000 ... Image Name: uboot ext2 ramdisk rootfs Image Type: ARM Linux RAMDisk Image (gzip compressed) Data Size: 28842031 Bytes = 27.5 MiB Load Address: 00000000 Entry Point: 00000000 Verifying Checksum ... OK Loading Kernel Image ... OK OK Starting kernel ...
代码过程
连接脚本 arch/arm/cpu/armv7/u-boot.lds
再看arch/arm/cpu/armv7/start.S 最后调用 arch/arm/lib/board.c的board_init_f().
该函数中，首先调用arch/arm/lib/board.c: init_sequence序列初始化,初始化gpmc/arch_cpu/timer/clk/env/serial/bandrate/console/display/print/board_info/i2c/dram等
init_fnc_t *init_sequence[] = {
#if defined(CONFIG_ARCH_CPU_INIT)
arch_cpu_init,
#endif
#if defined(CONFIG_BOARD_EARLY_INIT_F)
board_early_init_f,
#endif
timer_init,
#ifdef CONFIG_FSL_ESDHC
get_clocks,
#endif
env_init,
init_baudrate,
serial_init,
console_init_f,
display_banner,
#if defined(CONFIG_DISPLAY_CPUINFO)
print_cpuinfo,
#endif
#if defined(CONFIG_DISPLAY_BOARDINFO)
checkboard,
#endif
#if defined(CONFIG_HARD_I2C) || defined(CONFIG_SOFT_I2C)
init_func_i2c,
#endif
dram_init,
NULL,
};
然后保存ram_size 到gd，初始化gb->fb_base 等gb信息
最后调用relocate_code----》start.S里实现
为什么要relocate_code？
1.由x-loade可知，其将uboot前的部分代码（比如16k）拷贝到内部RAM的基地址，然后直接跳转到这个地址执行，但是一般的，uboot总是大于16K的，也就是说内部RAM不能完整执行uboot，需要把剩下的uboot搬移到外部RAM的高端地址执行。kernel是在DDR低地址执行的，为避免kernel与uboot地址重叠，需要把uboot搬移到DDR的高端地址执行。
2.某些uboot是从Nor等启动的，需要拷贝到DDR中才能完整执行。
参考[uboot] uboot relocation介绍_Andy_0755的博客-CSDN博客
uboot 跳转入ram执行代码分析(重映射分析)-erlei_2013-ChinaUnix博客
start.S中relocate_code段的如下代码，实现uboot的重定位，跳转到RAM中继续执行uboot
jump_2_ram:
ldr r0, _board_init_r_ofs
adr r1, _start
add lr, r0, r1
add lr, lr, r9
mov r0, r5
mov r1, r6
mov pc, lr
_start表示uboot.bin的绝对开始地址，_board_init_r_ofs是uboot.bin编译过程中生成的全部符号表board_init_r的地址，由此可以得出board_init_r与——start的偏移地址。
R9存储拷贝uboot到RAM中的地址，在根据函数的偏移地址，可以得出board_init_r函数在RAM中的地址，直接跳转到这个地址，即直接执行了board_init_r()函数。
该函数在arch/arm/lib/board.c中，
该函数继续初始化一些总线与外设，然后进入main_loop() ; 这里面执行bootm启动命令，从Nand等加载uImage执行内核启动。
