DTS修改- WRTNode（MT7620） 通过USB启动OpenWRT过程记录（上）

原文地址：http://blog.csdn.net/manfeel/article/details/30037001

接上篇文章，现在开始启动U盘中的kernel，又碰到了很多问题！

用 fatload usb 0 0x80000000 uImage.lzm ; bootm 0x80000000

总是碰到下面的错误：

MT7620 # bootm 0x80000000

## Booting image at 80000000 ...

   Image Name:   PandoraBox Linux-3.3.8

   Image Type:   MIPS Linux Kernel Image (lzma compressed)

   Data Size:    1058737 Bytes =  1 MB

   Load Address: 80000000

   Entry Point:  80000000

   Verifying Checksum ... OK

   Uncompressing Kernel Image ... LZMA ERROR 1 - must RESET board to recover

暂时没有找到问题所在，决定试试usbboot

usbboot usb 0

在U盘存在分区的情况下，输出如下：

MT7620 # usbboot usb 0

Loading from USB device 0, partition 1: Name: usbda1

  Type: U-Boot

First Block: 63, # of blocks: 2056257, Block Size: 512

** Bad Magic Number **

若没有分区，则输出如下：

MT7620 # usbboot usb 0

error reading partinfo...try to boot raw

Loading from USB device 0, partition 1: Name: Raw  Type: U-Boot

First Block: 0, # of blocks: 2880, Block Size: 512

** Bad Magic Number **

注意First Block！于是准备用RAW方式启动kernel

先把uImage写入U盘

sudo dd if=./uImage-mw305r.lzma of=/dev/sdc bs=512

然后再试图usbboot，但是，可悲的失败了！控制台输出：

MT7620 # usbboot usb 0

error reading partinfo...try to boot raw

Loading from USB device 0, partition 1: Name: Raw  Type: U-Boot

First Block: 0, # of blocks: 2880, Block Size: 512

   Image Name:   PandoraBox Linux-3.3.8

   Image Type:   MIPS Linux Kernel Image (lzma compressed)

   Data Size:    1058737 Bytes =  1 MB

   Load Address: 80000000

   Entry Point:  80000000

..............................................................................................................................................................................................................

MT7620 # 

识别出uImage，载入后，直接返回到UBoot控制台！Why？！

原来，在cmd_usb.c中的do_usbboot函数中，有如下判断：

/* Check if we should attempt an auto-start */

if (((ep = getenv("autostart")) != NULL) && (strcmp(ep,"yes") == 0)) {

    char *local_args[2];

    extern int do_bootm (cmd_tbl_t *, int, int, char *[]);

    local_args[0] = argv[0];

    local_args[1] = NULL;

    printf ("Automatic boot of image at addr 0x%08lX ...\n", addr);

    rcode=do_bootm (cmdtp, 0, 1, local_args);

    return rcode;

}

OK，环境变量中设置：

setenv autostart yes

然后再次尝试，可耻的再次失败！故障和fatload一样！

MT7620 # usbboot usb 0

error reading partinfo...try to boot raw

Loading from USB device 0, partition 1: Name: Raw  Type: U-Boot

First Block: 0, # of blocks: 2880, Block Size: 512

   Image Name:   PandoraBox Linux-3.3.8

   Image Type:   MIPS Linux Kernel Image (lzma compressed)

   Data Size:    1058737 Bytes =  1 MB

   Load Address: 80000000

   Entry Point:  80000000

..............................................................................................................................................................................................................

Automatic boot of image at addr 0x00000000 ...

## Booting image at 00000000 ...

   Image Name:   PandoraBox Linux-3.3.8

   Image Type:   MIPS Linux Kernel Image (lzma compressed)

   Data Size:    1058737 Bytes =  1 MB

   Load Address: 80000000

   Entry Point:  80000000

   Verifying Checksum ... OK

   Uncompressing Kernel Image ... LZMA ERROR 1 - must RESET board to recover

浏览代码之后，发现usbboot命令居然输入错了！

正确的格式是

usbboot loadaddress dev[:part]

故，应该这样输入：

usbboot 0x80000000 0

但结果还是一样的失败！再次失败！

在do_bootm的代码中，加入诊断代码，对比spi上的kernel和U盘上的kernel，观察控制台输出：

// manfeel , debug

printf("\nhdr->ih_load = 0x%08X\n",hdr->ih_load);

printf("data pointer = 0x%p\n",data);

printf("first 8 bytes data = %08X,%08X\n",((unsigned int*)data)[0],((unsigned int*)data)[1]);

printf("data length = %d\n", len);

i = lzmaBuffToBuffDecompress ((char*)ntohl(hdr->ih_load),

                &destLen, (char *)data, len);

if (i != LZMA_RESULT_OK) {

        printf ("LZMA ERROR %d - must RESET board to recover\n", i);

        SHOW_BOOT_PROGRESS (-6);

        udelay(100000);

        do_reset (cmdtp, flag, argc, argv);

}

# SPI上的kernel（正常启动）

hdr->ih_load = 00000080

data pointer = 80c00000

first 8 bytes data = 8000006D,313F4800

data length = 001027B1

# U盘上的kernel

hdr->ih_load = 0x00000080

data pointer = 0x80001040

first 8 bytes data = 8000006D,313F4800

data length = 1058737

LZMA ERROR 1 - must RESET board to recover

发现除了data的地址不一样以外，其他的都一模一样！试着修改了一下载入地址：

usbboot 0x80c00000 0

哈哈，kernel启动了！但最终会panic，正常，因为rootfs没有设定好。

在rt2880.h中似乎发现了一些load address的定义代码：

#if defined(RT6855A_FPGA_BOARD) || defined(RT6855A_ASIC_BOARD) || defined(MT7620_FPGA_BOARD) || defined(MT7620_ASIC_BOARD)

#define CFG_SPINAND_LOAD_ADDR    0x80c00000

接下来需要研究bootargs的问题了。