u-boot-2014.10移植第28天----nand flash启动（六）

硬件平台：tq2440

开发环境：Ubuntu-3.11

u-boot版本：2014.10

本文允许转载，请注明出处：http://blog.csdn.net/fulinus

我本来是想修改arch/arm/lib/relocate.S文件的，将nand flash中的镜像拷贝到SDRAM中运行，但是发现，前面4K空间中有board_init_f的C语言函数，函数里又有很多的库函数，这样一来牵扯的文件就很多了，很可能无法将他们全部包含在前4K空间内。我在arch/arm/lib/relocate.S文件中做的修改如下：

ENTRY(relocate_code)
    /* Check it's boot from SDRAM */
    ldr r1,=__image_copy_start
    ldr r2,=CONFIG_SYS_TEXT_BASE
    cmp r1,r2
    beq NORFLASH_BOOT

#ifdef CONFIG_S3C2440
    /* Check it's boot from Norflash or Nandflash:
     * If it's boot from Nandflash on S3C24X0 CPU,then the 4K internal SRAM(iSRAM) will 
     * mapped to both  address 0x4000003C and 0x0000003C. Read this start.S upside source 
     * code can see,the data in offset address 0x3C from the iSRAM should be 0xdeadbeef
     * (.balignl 16,0xdeadbeef). So if it's boot from Nandflash,if we modify the address 0x4000003C 
     * value to 0; then 0x0000003C value should be 0. For they are both in the iSRAM;
     * But if it's boot from Norflash,then the iSRAM is not mapped to 0x0000003C. So if modify address 
     * 0x4000003C(it's in iSRAM) value,the 0x0000003C(it's in Norflash) should be still 0xdeadbeef.
     */
judgment_norflash_nandflash_boot:
    ldr r1,=((4<<28)|(3<<4)|(3<<2)) /* address of Internal SRAM  0x4000003C*/
    mov r2,#0  /* r2 = 0 */
    str r2,[r1]

    mov r1,#0x3c   /* address of men  0x0000003C*/
    ldr r2,[r1]
    cmp r2,#0
    bne NORFLASH_BOOT

    /* recovery address 0x0000003C date*/
    ldr r2,=(0xdeadbeef)
    ldr r1,=( (4<<28)|(3<<4)|(3<<2) )
    str r2,[r1]

NANDFLASH_BOOT:
    /* Read u-boot from Nandflash to SDRAM address r0 */
    /* r0: nand_read_ll() 1st argument;
     * r1: nand_read_ll() 2nd argument;
     * r2: nand_read_ll() 3rd argument;
     */
    ldr r1,=__image_copy_start /* r1 <- SRC &__image_copy_start */
    subs    r4,r0,r1      /* r4 <- relocation offset */
    beq relocate_done       /* skip relocation */
    ldr r3,=__rel_dyn_end  /* r3 <- SRC &__rel_dyn_end */
    subs    r2,r3,r1      /* r2 = r3 - r1 <- u-boot length */

    bl  nand_read_ll

    tst r0,#0x0           /*Check nand_read_ll() return value*/
    bne infinite_loop     /*nand_read_ll() not return 0,then goto dead loop*/

nand_read_ok:
    /*Then verify the read data validation*/
    mov r0,#0             /* The first 4K data in internal SRAM*/
    ldr r1,=__image_copy_start
    add r1,r1,r4  /* The first 4K data read from Nandflash in SDRAM */
    mov r2,#0x400         /*The compare data length*/

compare_next_byte:
    ldr r3,[r0],#4
    ldr r5,[r1],#4
    teq r3,r5
    bne infinite_loop
    subs r2,r2,#4
? ? bne compare_next_byte


? ? /*
? ? ?* fix .rel.dyn relocations
? ? ?*/
? ? ldr r2,=__rel_dyn_start ? ?/* r2 <- SRC &__rel_dyn_start */
? ? add r2,r4 ?/* r2 = r2 + relocation offset */
? ? ldr r3,=__rel_dyn_end ?/* r3 <- SRC &__rel_dyn_end */
? ? add r3,r4 /* r3 = r3 + relocation offset */
? ? b fixloop


#define GPBDAT ?0x56000014
infinite_loop:
? ? ldr ? ? r2,=GPBDAT
? ? ldr ? ? r3,[r2]
? ? bic ? ? r3,#0x100 ? ? /*Set bit 5 as low level,Turn On LED*/
? ? str ? ? r3,[r2]
? ? b ? infinite_loop


#endif


NORFLASH_BOOT: ? ? ? ? ? ? ? ?/* relocate U-Boot from Flash to RAM */
? ? ldr r1,=__image_copy_start /* r1 <- SRC &__image_copy_start */
? ? subs ? ?r4,r1 ? ? ?/* r4 <- relocation offset */
? ? beq relocate_done ? ? ? /* skip relocation */
? ? ldr r2,=__image_copy_end ? /* r2 <- SRC &__image_copy_end */


copy_loop:
? ? ldmia ? r1!,{r10-r11} ? ? ?/* copy from source address [r1] ? ?*/
? ? stmia ? r0!,{r10-r11} ? ? ?/* copy to ? target address [r0] ? ?*/
? ? cmp r1,r2 ? ? ? ? ?/* until source end address [r2] ? ?*/
? ? blo copy_loop


? ? /*
? ? ?* fix .rel.dyn relocations
? ? ?*/
? ? ldr r2,=__rel_dyn_start ? ?/* r2 <- SRC &__rel_dyn_start */
? ? ldr r3,=__rel_dyn_end ?/* r3 <- SRC &__rel_dyn_end */


fixloop:
? ? ldmia ? r2!,{r0-r1} ? ? ? ?/* (r0,r1) <- (SRC location,fixup) */
? ? and r1,#0xff
? ? cmp r1,#23 ? ? ? ? /* relative fixup? */
? ? bne fixnext


? ? /* relative fix: increase location by offset */
? ? add r0,r4
? ? ldr r1,[r0]
? ? add r1,r4
? ? str r1,[r0]
fixnext:
? ? cmp r2,r3
? ? blo fixloop


relocate_done:

没有其他好的方法，只能好好的研究一下如何实现SPL启动。

明天继续。