u-boot-2011.03在mini2440/micro2440上的移植（七）——支持Nand Flash启动

7.1 创建nand_read.c

【注意】
本程序只能用于读取2K/页的Nand。本人的Micro2440上的Nand Flash为256M，型号为K9F2G08
 

[408@WZC u-boot-2011.06]$ touch board/samsung/micro2440/nand_read.c
[408@WZC u-boot-2011.06]$ cat> board/samsung/micro2440/nand_read.c

 

#define rNFCONF  (*(volatile unsigned *)0x4E000000)
#define rNFCONT  (*(volatile unsigned *)0x4E000004)
#define rNFCMD  (*(volatile unsigned *)0x4E000008)
#define rNFADDR  (*(volatile unsigned *)0x4E00000C)
#define rNFDATA8 (*(volatile unsigned char*)0x4E000010)
#define rNFSTAT  (*(volatile unsigned *)0x4E000020)

#define CMD_READ1   0x00            /* 页读命令周期1 */
#define CMD_READ2   0x30            /* 页读命令周期2 */
#define CMD_RESET   0xFF          /* 复位    */

#define NF_CMD(cmd)   {rNFCMD=(cmd);}     /* 写命令   */
#define NF_ADDR(addr)  {rNFADDR=(addr);}    /* 写地址   */
#define NF_RDDATA8()  (rNFDATA8)         /* 读8位数据  */
#define NF_nFCE_L()   {rNFCONT&=~(1<<1);}    /* 片选使能   */
#define NF_nFCE_H()   {rNFCONT|=(1<<1);}    /* 片选禁用   */
#define NF_WAITRB()      {while(!(rNFSTAT&(1<<1)));}  /* 等待就绪   */
#define NF_CLEAR_RB()     {rNFSTAT |= (1<<2);}   /* 清除就绪/忙位 */
#define NF_DETECT_RB()     {while(!(rNFSTAT&(1<<2)));}  /* 等待就绪   */

#define TACLS  1
#define TWRPH0  2
#define TWRPH1  1

void delay(int i)
{
 while(i-->0);
}

void Nand_Init(void)
{
 rNFCONF = (TACLS<<12)|(TWRPH0<<8)|(TWRPH1<<4)|(0<<0); 
 rNFCONT = (1<<4)|(1<<1)|(1<<0);
}

static void Nand_Reset(void)
{
 NF_nFCE_L();      /* 片选使能   */
 NF_CLEAR_RB();      /* 清除就绪/忙位  */
 NF_CMD(CMD_RESET);     /* 写复位命令  */
 NF_DETECT_RB();      /* 等待就绪   */
 NF_nFCE_H();      /* 片选禁用   */
}

unsigned char Nand_ReadPage(const int page, unsigned char * const buffer)
{
 int i;
 
 Nand_Reset();
 
 NF_nFCE_L();
 NF_CLEAR_RB();

 NF_CMD(CMD_READ1); 
 NF_ADDR(0x0);
 NF_ADDR(0x0);
 NF_ADDR(page&0xff);
 NF_ADDR((page>>8)&0xff);
 NF_ADDR((page>>16)&0xff);
 NF_CMD(CMD_READ2); 
   
 NF_DETECT_RB();

 for (i = 0; i < 2048; i++) 
 {
  buffer[i] =  NF_RDDATA8();
 }
 
 NF_nFCE_H();
}

int nand_read(int start_page, int read_pages, unsigned char *buffer)
{
 int i;

 Nand_Init();
 for(i=0; i<read_pages; i++)
 {
  Nand_ReadPage(start_page, buffer + 2048*i);
  start_page++;
 }
 return 0;
}

 

7.2 board/samsung/micro2440/Makefile

COBJS := micro2440.o flash.o nand_read.o

 

7.3 arch/arm/cpu/arm920t/u-boot.lds

 .text :
 {
  arch/arm/cpu/arm920t/start.o (.text)
  board/samsung/micro2440/libmicro2440.o    (.text)
  *(.text)
 }

 

【说明】

如果是在RAM中运行，一定要删去board/samsung/micro2440/libmicro2440.o    (.text)，否则在RAM中也不能运行。原因尚不理解，需要阅读代码。

 

7.4 arch/arm/cpu/arm920t/start.S

下面红色部分是添加的部分，黑色的代码用于定位。

#ifndef CONFIG_SKIP_LOWLEVEL_INIT
    bl cpu_init_crit
#endif

 

#ifdef CONFIG_S3C2440_NAND_BOOT 
    ldr sp, =0x30008000 
    ldr r0, =0x0; 
    ldr r1, _end_ofs 
    mov r1, r1, LSR #11 
    add r1, r1, #1 
    ldr r2, =(CONFIG_SYS_TEXT_BASE) 
    bl nand_read 
    ldr pc, =relocations 
#endif
......
......
copy_loop: 
ldmia r0!, {r9-r10} /* copy from source address [r0] */ 
stmia r1!, {r9-r10} /* copy to target address [r1] */ 
cmp r0, r2 /* until source end address [r2] */ 
blo copy_loop 

#ifdef CONFIG_S3C2440_NAND_BOOT 
relocations: 
    ldr r6, =CONFIG_SYS_TEXT_BASE 
#endif 

#ifndef CONFIG_PRELOADER 
/* 
* fix .rel.dyn relocations 
*/
......
......
clbss_l:str r2, [r0] /* clear loop... */ 
add r0, r0, #4 
cmp r0, r1 
bne clbss_l 

bl coloured_LED_init 
bl red_LED_on 
#endif 

#ifdef CONFIG_S3C2440_NAND_BOOT 
    ldr sp, =(CONFIG_SYS_INIT_SP_ADDR) 
    bic sp, sp, #7 /* 8-byte alignment for ABI compliance */ 
    ldr r0,=0x00000000 
   ldr pc, =board_init_f 
#endif 

/* 
* We are done. Do not return, instead branch to second part of board 
* initialization, now running from RAM. 
*/ 
#ifdef CONFIG_NAND_SPL

 

7.5 include/configs/micro2440.h

#define CONFIG_S3C2440_NAND_BOOT/* #define CONFIG_SKIP_LOWLEVEL_INIT */

【说明】
由于要在Nand Flash中运行，所以需要注释掉#define CONFIG_SKIP_LOWLEVEL_INIT

7.6 arch/arm/lib/board.c

void board_init_f (ulong bootflag) 
{ 
    ...... 

    gd->mon_len = _bss_end_ofs + 0x100000; /* why */ 

    ...... 

这里的修改参考了bscbem的日志：http://my.chinaunix.net/space.php?uid=24319701&do=blog&id=136249如果有读者想了解原理请参考这个日志。
 
    /* relocate_code (addr_sp, id, addr); */#ifdef CONFIG_S3C2440_NAND_BOOT /*add by wzc*/     __asm__ __volatile__("mov sp,%0"::"r"(addr_sp):"sp");/*add by wzc*/     board_init_r(id, addr); #else     relocate_code (addr_sp, id, addr);     /* NOTREACHED - relocate_code() does not return */ #endif}
【说明】
至于gd->mon_len = _bss_end_ofs + 0x100000;我也不理解，需要阅读源代码才能解释。

7.7 下载到Nand Flash

 到这里应该就可以从Nand Flash启动了。