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uboot 自引导内核（小寿原创）

首先介绍如何将内核写进nand flash：
u-boot# nand erase 0x00030000 0x00100000
u-boot# tftp 0x31000000 zImage
u-boot# nand write 0x31000000 0x00030000 0x00100000

这里我们有几种方法来实现自引导：

1.采用go的方法：
u-boot# tftp 0x31000000 zImage
u-boot# go 0x31000000
这是直接从内存引导的内核，我们可以将内核写进nand flash 让他自引导：
u-boot# nand erase 0x00030000 0x100000
u-boot# nand write 0x31000000 0x00030000 0x00100000
u-boot# setenv bootcmd nand read 0x30008000 0x00030000 0x00100000/;go 0x30008000
u-boot# saveenv
u-boot# boot

2.采用bootm的方法：
首先我们需要用u-boot-1.2.0/tools/mkimage 工具来处理一下我们的内核文件zImage；

# mkimage -n 'linux-2.6.14' -A arm -O linux -T kernel -C none -a 0x30008000 -e 0x30008000 -d zImage zImage.img

Image Name:   linux-2.6.14
Created:      Fri Jan 12 17:14:50 2007
Image Type:   ARM Linux Kernel Image (uncompressed)
Data Size:    1262504 Bytes = 1232.91 kB = 1.20 MB
Load Address: 0x30008000
Entry Point: 0x30008000
这里解释一下参数的意义：
         -A ==> set architecture to 'arch'
        -O ==> set operating system to 'os'
        -T ==> set image type to 'type'
        -C ==> set compression type 'comp'
        -a ==> set load address to 'addr' (hex)
        -e ==> set entry point to 'ep' (hex)
        -n ==> set image name to 'name'
        -d ==> use image data from 'datafile'
        -x ==> set XIP (execute in place)

接着我们来通过u-boot来将内核zImage.img下载到内存中:
u-boot# tftp 0x31000000 zImage.img
u-boot# bootm 0x31000000

   Booting image at 31000000 ...
Image Name:   linun-2.6.14
Image Type:   ARM Linux Kernel Image (uncompressed)
Data Size:    1263260 Bytes = 1.2 MB
Load Address: 30008000
Entry Point: 30008000
Verifying Checksum ... OK
OK
Starting kernel ...
Uncompressing Linux.............................................................

下面是自引导的实现：
u-boot# nand erase 0x00030000 0x100000
u-boot# nand write 0x31000000 0x00030000 0x00100000
u-boot# setenv bootcmd nand read 0x31000000 0x30000 0x100000/;bootm 0x31000000
u-boot# saveenv
u-boot# boot