1、下载内核源代码，选定Linux 2.6.20.（）
2、打补丁。下载对应版本的补丁。网上好像失效，在PUDN上下载了补丁，放在这里。
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| 文件: |
2.6.20-at91.rar |
| 大小: |
53KB |
| 下载: |
下载 | |
3、移植好，之后，加载到开发板上，出现问题：
Error: unrecognized/unsupported machine ID
原因：
This kind of error message happens if the machine ID which is set in U-Boot doesn't match the kernel's ID(s). Unfortunately a standard U-Boot sets the machine ID on AT91RM9200DK boards not to MACH_TYPE_AT91RM9200DK but to the generic MACH_TYPE_AT91RM9200. You can either this in board/at91rm9200dk/at91rm9200dk.c; I would recommend to obtain a new machine ID and create your own U-Boot board type, using board/at91rm9200dk as a template. The list of machine IDs can be found in include/asm-arm/mach-types.h.
The Linux kernel has to be changed accordingly to the above machine ID. There you can find the information in arch/arm/tools/mach-types arch/arm/boot/compressed/head-at91rm9200.S arch/arm/mach-at91rm9200/board-dk.c
具体资料如下：
U-boot端include/asm-arm/mach-types.h支持的at91rm9200的machine类型有：
#define MACH_TYPE_AT91RM9200 251
#define MACH_TYPE_AT91RM9200DK 262
但是在board/at91rm9200dk/at91rm9200dk.c中，虽然注释中说明使用的是AT91RM9200DK-Board，但是实际使用的是MACH_TYPE_AT91RM9200。
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int board_init (void)
{
/* Enable Ctrlc */
console_init_f ();
/* Correct IRDA resistor problem */
/* Set PA23_TXD in Output */
((AT91PS_PIO) AT91C_BASE_PIOA)->PIO_OER = AT91C_PA23_TXD2;
/* memory and cpu-speed are setup before relocation */
/* so we do _nothing_ here */
/* arch number of AT91RM9200DK-Board */
gd->bd->bi_arch_number = MACH_TYPE_AT91RM9200;
/* adress of boot parameters */
gd->bd->bi_boot_params = PHYS_SDRAM + 0x100;
return 0;
}
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Linux内核端：
arch/arm/tools/mach-types支持的at91rm9200的machine的ID有：
at91rm9200 ARCH_AT91RM9200 AT91RM9200 251
at91rm9200dk ARCH_AT91RM9200DK AT91RM9200DK 262
at91rm9200tb ARCH_AT91RM9200TB AT91RM9200TB 380
at91rm9200kr MACH_AT91RM9200KR AT91RM9200KR 450
at91rm9200ek MACH_AT91RM9200EK AT91RM9200EK 705
at91rm9200utl MACH_AT91RM9200UTL AT91RM9200UTL 821
at91rm9200kg MACH_AT91RM9200KG AT91RM9200KG 975
at91rm9200rb MACH_AT91RM9200RB AT91RM9200RB 1060
at91rm9200df MACH_AT91RM9200DF AT91RM9200DF 1119
arch/arm/boot/compressed/head-at91rm9200.S支持的有：
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.section ".start", "ax"
@ Atmel AT91RM9200-DK : 262
mov r3, #(MACH_TYPE_AT91RM9200DK & 0xff)
orr r3, r3, #(MACH_TYPE_AT91RM9200DK & 0xff00)
cmp r7, r3
beq 99f
@ Cogent CSB337 : 399
mov r3, #(MACH_TYPE_CSB337 & 0xff)
orr r3, r3, #(MACH_TYPE_CSB337 & 0xff00)
cmp r7, r3
beq 99f
@ Cogent CSB637 : 648
mov r3, #(MACH_TYPE_CSB637 & 0xff)
orr r3, r3, #(MACH_TYPE_CSB637 & 0xff00)
cmp r7, r3
beq 99f
@ Atmel AT91RM9200-EK : 705
mov r3, #(MACH_TYPE_AT91RM9200EK & 0xff)
orr r3, r3, #(MACH_TYPE_AT91RM9200EK & 0xff00)
cmp r7, r3
beq 99f
@ Conitec Carmeva : 769
mov r3, #(MACH_TYPE_CARMEVA & 0xff)
orr r3, r3, #(MACH_TYPE_CARMEVA & 0xff00)
cmp r7, r3
beq 99f
@ KwikByte KB920x : 612
mov r3, #(MACH_TYPE_KB9200 & 0xff)
orr r3, r3, #(MACH_TYPE_KB9200 & 0xff00)
cmp r7, r3
beq 99f
@ Embest ATEB9200 : 923
mov r3, #(MACH_TYPE_ATEB9200 & 0xff)
orr r3, r3, #(MACH_TYPE_ATEB9200 & 0xff00)
cmp r7, r3
beq 99f
@ Sperry-Sun KAFA : 662
mov r3, #(MACH_TYPE_KAFA & 0xff)
orr r3, r3, #(MACH_TYPE_KAFA & 0xff00)
cmp r7, r3
beq 99f
@ Ajeco 1ARM : 1075
mov r3, #(MACH_TYPE_ONEARM & 0xff)
orr r3, r3, #(MACH_TYPE_ONEARM & 0xff00)
cmp r7, r3
beq 99f
@ Unknown board, use the AT91RM9200DK board
@ mov r7, #MACH_TYPE_AT91RM9200
mov r7, #(MACH_TYPE_AT91RM9200DK & 0xff)
orr r7, r7, #(MACH_TYPE_AT91RM9200DK & 0xff00)
99:
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真正的配置信息是在arch/arm/mach-at91rm9200/board-dk.c中。
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MACHINE_START(AT91RM9200DK, "Atmel AT91RM9200-DK")
/* Maintainer: SAN People/Atmel */
.phys_io = AT91_BASE_SYS,
.io_pg_offst = (AT91_VA_BASE_SYS >> 18) & 0xfffc,
.boot_params = AT91_SDRAM_BASE + 0x100,
.timer = &at91rm9200_timer,
.map_io = dk_map_io,
.init_irq = dk_init_irq,
.init_machine = dk_board_init,
MACHINE_END
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由此可以看出，Uboot使用的AT91RM9200的machine ID，而内核配置的是at91rm9200 dk的machine
ID，在这种情况下就出现了不一致。所以更改的方法：
方法一、把Uboot中board init中更改为MACH_TYPE_AT91RM9200DK
方法二、把MACHINE_START(AT91RM9200DK, "Atmel AT91RM9200-DK")更改为MACHINE_START(AT91RM9200, "Atmel AT91RM9200-DK")。
只要U-boot和Linux kernel一致即可。
