3.2Bootloader拷贝

配置为从NAND FLASH启动，需要将NAND FLASH中的vivi代码copy到RAM中：

#ifdef CONFIG_S3C2410_NAND_BOOT

bl copy_myself

@ jump to ram

ldr r1, =on_the_ram

add pc, r1, #0

nop

nop

1: b 1b @ infinite loop

#ifdef CONFIG_S3C2410_NAND_BOOT

@

@ copy_myself: copy vivi to ram

@

copy_myself:

mov r10, lr

@ reset NAND

mov r1, #NAND_CTL_BASE

ldr r2, =0xf830 @ initial value

str r2, [r1, #oNFCONF]

ldr r2, [r1, #oNFCONF]

bic r2, r2, #0x800 @ enable chip

str r2, [r1, #oNFCONF]

mov r2, #0xff @ RESET command

strb r2, [r1, #oNFCMD]

mov r3, #0 @ wait

1: add r3, r3, #0x1

cmp r3, #0xa

blt 1b

2: ldr r2, [r1, #oNFSTAT] @ wait ready

tst r2, #0x1

beq 2b

ldr r2, [r1, #oNFCONF]

orr r2, r2, #0x800 @ disable chip

str r2, [r1, #oNFCONF]

@ get read to call C functions (for nand_read())

ldr sp, DW_STACK_START @ setup stack pointer

mov fp, #0 @ no previous frame, so fp=0

@ copy vivi to RAM

ldr r0, =VIVI_RAM_BASE

mov r1, #0x0

mov r2, #0x20000

bl nand_read_ll

tst r0, #0x0

beq ok_nand_read

#ifdef CONFIG_DEBUG_LL

bad_nand_read:

ldr r0, STR_FAIL

ldr r1, SerBase

bl PrintWord

1: b 1b @ infinite loop

#endif

ok_nand_read:

#ifdef CONFIG_DEBUG_LL

ldr r0, STR_OK

ldr r1, SerBase

bl PrintWord

#endif

@ verify

mov r0, #0

ldr r1, =0x33f00000

mov r2, #0x400 @ 4 bytes * 1024 = 4K-bytes

go_next:

ldr r3, [r0], #4

ldr r4, [r1], #4

teq r3, r4

bne notmatch

subs r2, r2, #4

beq done_nand_read

bne go_next

notmatch:

#ifdef CONFIG_DEBUG_LL

sub r0, r0, #4

ldr r1, SerBase

bl PrintHexWord

ldr r0, STR_FAIL

ldr r1, SerBase

bl PrintWord

#endif

1: b 1b

done_nand_read:

#ifdef CONFIG_DEBUG_LL

ldr r0, STR_OK

ldr r1, SerBase

bl PrintWord

#endif

mov pc, r10

@ clear memory

@ r0: start address

@ r1: length

mem_clear:

mov r2, #0

mov r3, r2

mov r4, r2

mov r5, r2

mov r6, r2

mov r7, r2

mov r8, r2

mov r9, r2

clear_loop:

stmia r0!, {r2-r9}

subs r1, r1, #(8 * 4)

bne clear_loop

mov pc, lr

#endif @ CONFIG_S3C2410_NAND_BOOT

　3.3进入C代码

首先要设置堆栈指针sp，堆栈指针的设置是为了执行C语言代码作好准备。设置好堆栈后，调用C语言的main函数：

@ get read to call C functions

ldr sp, DW_STACK_START @ setup stack pointer

mov fp, #0 @ no previous frame, so fp=0

mov a2, #0 @ set argv to NULL

bl main @ call main

mov pc, #FLASH_BASE @ otherwise, reboot