这里采用另外一种办法，原理详见tekkamannjnia的博客：
也是主要改start.s文件，代码也参考了tekkamannjnia的uboot移植的相关代码。
start.s文件：
- /******************************************************************
-
*定义各模式堆栈空间
-
*******************************************************************/
-
.equ FIQ_STACK, 0x36FFF000
-
.equ IRQ_STACK, 0x36FFE000
-
.equ ABORT_STACK, 0x36FFD000
-
.equ UNDEFINE_STACK, 0x36FFC000
-
.equ USER_STACK, 0x36FFB000
-
.equ SVC_STACK, 0x36FFA000
-
/******************************************************************
-
*中断向量表
-
*******************************************************************/
-
.text
-
.global _start
-
_start: b start_code @0x00,复位异常
-
ldr pc, _undefined_instruction @0x04，未定义指令异常
-
ldr pc, _software_interrupt @0x08，软中断
-
ldr pc, _prefetch_abort @0x0c，指令预取终止异常
-
ldr pc, _data_abort @0x10，数据访问终止异常
-
ldr pc, _not_used @0x14，保留
-
ldr pc, _irq @0x18，中断
-
ldr pc, _fiq @0x1c，快速中断
-
_undefined_instruction: .word undefined_instruction
-
_software_interrupt: .word software_interrupt
-
_prefetch_abort: .word prefetch_abort
-
_data_abort: .word data_abort
-
_not_used: .word not_used
-
_irq: .word irq
-
_fiq: .word fiq
-
-
.balignl 16, 0xdeadbeef
-
/******************************************************************
-
*代码开始
-
*******************************************************************/
-
start_code:
-
mrs r0, cpsr @设置为管理模式
-
bic r0, r0, #0x1F @ARM指令，禁止中断
-
orr r0, r0, #0xD3
-
msr cpsr, r0
-
-
ldr r0, =0x53000000 @关闭看门狗
-
mov r1, #0x0
-
str r1, [r0]
-
-
ldr r0, =0x4C000014 @设置时钟分频比
-
mov r1, #0x05 @FCLK:HCLK:PCLK = 1:4:8
-
str r1, [r0]
-
-
mrc p15, 0, r0, c1, c0, 0 @如果HDIVN不为0，使其从
-
orr r0, r0, #0xC0000000 @由快总线模式变为异步总线模式
-
mcr p15, 0, r0, c1, c0, 0
-
-
ldr r0, =0x4C000008 @设置UCLK=48MHz
-
ldr r1, =0x00038022 @(56<<12)|(2<<4)|(2)
-
str r1, [r0]
-
-
ldr r0, =0x4C000004 @设置FCLK=400MHz
-
ldr r1, =0x0005C011 @(92<<12)|(1<<4)|(1)
-
str r1, [r0]
-
-
mov r1, #0x48000000 @设置SDRAM
-
adrl r2, mem_cfg_val
-
add r3, r1, #52
-
1:
-
ldr r4, [r2], #4
-
str r4, [r1], #4
-
cmp r1, r3
-
bne 1b
-
/******************************************************************
-
*判断是从norflash还是从nandflash启动，然后复制代码到SDRAM，跳入第二阶段执行
-
*******************************************************************/
-
ldr r1, =((4<<28)|(3<<4)|(3<<2)) //SRAM地址0X4000003C写0
-
mov r0, #0
-
str r0,[r1]
-
-
mov r1, #0x3C //读取地址0X0000003C处的值是否为0，若不是，则从norflash启动
-
ldr r0,[r1]
-
cmp r0,#0
-
bne relocate
-
-
ldr r0, =(0xdeadbeef) //若为0，则从nandflash启动，并恢复地址0X4000003C处原来的值
-
ldr r1, =((4<<28)|(3<<4)|(3<<2))
-
str r0, [r1]
-
-
/*#define BWSCON 0x48000000
-
ldr r0, =BWSCON
-
ldr r0, [r0]
-
ands r0, r0, #6
-
cmp r0, #0
-
bne copy_loop*/
-
-
ldr sp, =4096 //从nandflash中复制代码到SDRAM中
-
bl s3c2440_nand_init
-
ldr r0, =0x30000000
-
mov r1, #4096
-
mov r2, #2048
-
bl s3c2440_nand_read
-
b laststep
-
-
not_match: //如果从norflash中验证0x0000003c处不是0xdeadbeef,则出错
-
error:
-
b error
-
-
relocate:
-
ldr r1, =(0xdeadbeef) //验证0x0000003c处是不是0xdeadbeef
-
cmp r0, r1
-
bne error
-
-
ldr r0, =4096 //从norflash中复制代码到SDRAM
-
ldr r1, =0x30000000
-
mov r2, #102400
-
-
copy_loop:
-
ldmia {r3-r10}
-
stmia {r3-r10}
-
cmp r0, r2
-
ble copy_loop
-
-
laststep:
-
ldr lr, =halt_loop
-
ldr pc, =main
-
-
halt_loop:
-
b halt_loop
-
-
/*******************************************************************
-
*存储控制器13个寄存器的设置值
-
********************************************************************/
-
.align 4
-
mem_cfg_val:
-
.long 0x22011110
-
.long 0x00000700
-
.long 0x00000700
-
.long 0x00000700
-
.long 0x00000700
-
.long 0x00000700
-
.long 0x00000700
-
.long 0x00018005
-
.long 0x00018005
-
.long 0x008C07A3
-
.long 0x000000B2
-
.long 0x00000030
-
.long 0x00000030
-
-
/******************************************************************
-
*设置各模式堆栈
-
*******************************************************************/
-
stack_setup:
-
mrs r0, cpsr
-
bic r0, r0, #0x1F
-
orr r0, r0, #0xDB
-
msr cpsr, r0
-
ldr sp, =UNDEFINE_STACK
-
-
mrs r0, cpsr
-
bic r0, r0, #0x1F
-
orr r0, r0, #0xD7
-
msr cpsr, r0
-
ldr sp, =ABORT_STACK
-
-
mrs r0, cpsr
-
bic r0, r0, #0x1F
-
orr r0, r0, #0xD2
-
msr cpsr, r0
-
ldr sp, =IRQ_STACK
-
-
mrs r0, cpsr
-
bic r0, r0, #0x1F
-
orr r0, r0, #0xD1
-
msr cpsr, r0
-
ldr sp, =FIQ_STACK
-
-
mrs r0, cpsr
-
bic r0, r0, #0x1F
-
orr r0, r0, #0xD0
-
msr cpsr, r0
-
ldr sp, =USER_STACK
-
-
mrs r0, cpsr
-
bic r0, r0, #0x1F
-
orr r0, r0, #0xD3
-
msr cpsr, r0
-
ldr sp, =SVC_STACK
-
/*******************************************************************
-
*中断处理
-
********************************************************************/
-
undefined_instruction:
-
b undefined_instruction
-
software_interrupt:
-
b software_interrupt
-
prefetch_abort:
-
b prefetch_abort
-
data_abort:
-
b data_abort
-
not_used:
-
b not_used
-
irq:
-
b irq
-
fiq:
-
b fiq
程序就是思想方法的一种具体体现。。。。。，所以有思想才是最重要的。
附源代码：
好，前面的几个目标都实现了，继续下一步，加油。
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