UBoot200903移植笔记（从Nandflash启动一）

在U-Boot-2009-03移植笔记（点亮第一展灯）中，我们初始化好了sdram，点亮了第一盏灯。在本文中，我们将移植好nandflash启动的驱动代码。

对于S3C2440，有一个steppingston,在CPU上电的时候，由硬件将Nandflash的前4KB代码拷贝到片内的SRAM中，并且内部SRAM被映射到地址0x0，于是我们的代码才能被cpu执行。

但问题是我们的代码肯定不止4KB，所以我们必须自己写代码，把nandflash中的剩余代码拷贝到内存中，然后让CPU跳转到对应的内存地址执行。

设置堆栈指针，为C语言准备运行环境

        /*设置堆栈*/
    ldr sp, DW_STACK_START
    mov fp,#0    

注意第二行引用了DW_STACK_START标号，我们定义在标号_start_armboot后面

_start_armboot:    .word start_armboot
DW_STACK_START: .word STACK_BASE+STACK_SIZE-4

第二行的STACK_BASE和STACK_SIZE都定义在include/configs/xinna2440.h中

#define STACK_BASE  0x33f00000     //定义堆栈的地址
#define STACK_SIZE  0x8000         //堆栈的长度大小

 设置好了堆栈指针，下面我们只需要初始化好Nandflash之后，就可以读取数据，存到sdram中了。

初始化NandFlash

我们在board/xinna2440/文件夹下，增加nand_op.c文件，然后修改board/xinna2440/Makefile,添加对nand_op.c的编译

COBJS        := xinna2440.o flash.o nand_op.o

编辑board/xinna2440/nand_op.c，添加以下文件,我们的板子上用的是K9F2G08U0A，2KB一页，共64MB大小。  1 /*

 * board/samsung/reille2440/nand_read.c
 *
 * (C) Copyright 2011
 * reille <http://blog.csdn.net/reille/> <reille@qq.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 */
#include <config.h>
#define NF_BASE   0x4E000000  //Nand Flash配置寄存器基地址
#define __REGb(x) (*(volatile unsigned char *)(x))
#define __REGi(x) (*(volatile unsigned int  *)(x))
#if 0
#define NFCONF __REGi(NF_BASE + 0x0 )  //通过偏移量还是得到配置寄存器基地址
#define NFCONT __REGi(NF_BASE + 0x4 )  //通过偏移量得到控制寄存器基地址
#define NFCMD  __REGb(NF_BASE + 0x8 )  //通过偏移量得到指令寄存器基地址
#define NFADDR __REGb(NF_BASE + 0xC )  //通过偏移量得到地址寄存器基地址
#define NFDATA __REGb(NF_BASE + 0x10)  //通过偏移量得到数据寄存器基地址
#define NFSTAT __REGb(NF_BASE + 0x20)  //通过偏移量得到状态寄存器基地址
#endif

#define NFCONF (*(volatile unsigned int *)(NF_BASE + 0X0))
#define NFCONT (*(volatile unsigned short *)(NF_BASE + 0x4))
#define NFCMD  (*(volatile unsigned short *)(NF_BASE + 0X8))
#define NFADDR (*(volatile unsigned short *)(NF_BASE + 0xc))
#define NFDATA (*(volatile unsigned char *)(NF_BASE + 0x10))
#define NFSTAT (*(volatile unsigned char *)(NF_BASE + 0x20))


#define NAND_CHIP_ENABLE  (NFCONT &= ~(1<<1))  //Nand片选使能
#define NAND_CHIP_DISABLE (NFCONT |= (1<<1))   //取消Nand片选
#define NAND_CLEAR_RB     (NFSTAT |= (1<<2));
#define NAND_DETECT_RB    { while(! (NFSTAT&(1<<2)) );}
#define NAND_SECTOR_SIZE 2048
#define NAND_BLOCK_MASK (NAND_SECTOR_SIZE - 1)
#if 0
#define DEBUGN    printf
#else
#define DEBUGN(x, args ...) {}
#endif

/* low level nand read function */
#define GPBCON  (*(volatile unsigned long *)0x56000010)
#define GPBDAT  (*(volatile unsigned long *)0x56000014)

#define GPACON    (*(volatile unsigned long *)0x56000000)

void nand_wait_ll(void)
{
    int k;
    while(!(NFSTAT & 1))
        for(k = 0; k < 20; k++);
    return;
//    NAND_DETECT_RB
}

void nand_reset_ll(void)
{
    NAND_CHIP_ENABLE; //选中Nand片选
//    NAND_CLEAR_RB 
    NFCMD = 0xff;
    nand_wait_ll();
//    NAND_CLEAR_RB 
    NAND_CHIP_DISABLE; //取消片选信号
}


unsigned char nand_read_id(unsigned char*mc,unsigned char *dc,unsigned char *pc)
{
    int i=0;
    unsigned char res;
    NAND_CHIP_ENABLE; //选中Nand片选
    NFCMD = 0x90;
    for(i = 0;i < 100;i++);
    NFADDR = 0 & 0xFF;
    NFADDR = (0 >> 9) & 0xFF;
    NFADDR = (0 >> 17) & 0xFF;
    NFADDR = (0 >> 25) & 0xFF;
    for(i = 0;i < 100;i++);
    nand_wait_ll();
    *mc = NFDATA;
    *dc = NFDATA;
    res = NFDATA;
    *pc = NFDATA;
    NAND_CHIP_DISABLE; //取消片选信号
    return *mc;
}

void nand_init_ll(void)
{
    int TACLS = 3;
    int TWRPH0 = 7;
    int TWRPH1 = 7;
    int i = 0;
    //配置gpio
//    GPACON = (GPACON &~(0x3f << 17)) | ( 0x3f << 17);
    GPACON = GPACON | (0x3f << 17);
    NFCONF = (TACLS << 12) | (TWRPH0 << 8) | (TWRPH1 << 4) | (0 << 0);

    NFCONT = (0 << 13) | (0 << 12) | ( 0 << 10) | (0 << 9) | (0 << 8) | (1 << 6) | (1 << 5) | (1 << 4) | (1 << 1) | (1 << 0);

    nand_reset_ll();
}

#if 0
int nand_write_ll(void)
{
    int i = 0x90000;
    unsigned char j = 0;
    NAND_CHIP_ENABLE; //选中Nand片选
    NFCMD = 0x80;

    NFADDR = 0x00;
    NFADDR = 0x00;
    NFADDR = i & 0xFF;
    NFADDR = (i >> 8) & 0xFF;
    NFADDR = (i >> 16) & 0xFF;
    for(j = 0; j < 100;j++);


    NFCMD = 0x10;
    nand_wait_ll();

    for(j = 0 ; j < 100; j++)
    {
        NFDATA = j;
    }
    NFCMD = 0x10;
    nand_wait_ll();

    NAND_CHIP_DISABLE; //取消片选信号
    return 0;
}
#endif

static void write_addr(unsigned int addr)
{
    int col,page,i;
    col = addr & NAND_BLOCK_MASK;
    page = addr & NAND_SECTOR_SIZE;

    NFADDR = col & 0xff;
    for(i = 0; i < 10; i++);
    NFADDR = (col >> 8) & 0x0f;
    for(i = 0; i < 10; i++);


    NFADDR = page & 0xFF;
    for(i = 0; i < 10; i++);
    NFADDR = (page >> 8) & 0xFF;
    for(i = 0; i < 10; i++);

    NFADDR = (page >> 16) & 0x01;
    for(i = 0; i < 10; i++);
}

static nand_read_page_ll(unsigned char *buf,unsigned long pageaddr)
{
    int i = 0;
    NAND_CHIP_ENABLE; //选中Nand片选

    //发出READ0指令
    NFCMD = 0;

    //对Nand进行寻址
    NFADDR = 0x00;
    NFADDR = 0x00;
    NFADDR = pageaddr & 0xff;
    NFADDR = (pageaddr >> 8) & 0xff;
    NFADDR = (pageaddr >> 16) & 0xff;

    NFCMD = 0x30;
    nand_wait_ll();
        
    for(i=0; i < NAND_SECTOR_SIZE; i++)
        buf[i] = NFDATA;

    NAND_CHIP_DISABLE; //取消片选信号
}

int nand_read_ll(unsigned char *buf, unsigned long start_addr, int size)
{
    int pageaddr = 0;
    for(pageaddr = 0; pageaddr < 100;pageaddr++)
    {
        nand_read_page_ll(buf,pageaddr);
        buf += NAND_SECTOR_SIZE;
    }
    return 0;
}

 写好了nand_flash驱动之后，我们在start.S中调用，将u-boot自身，从nandflash读到sdram中。

    bl nand_init_ll     /*调用nandflash初始化函数*/

    ldr r0, =TEXT_BASE  /*指定uboot在内存中的地址，这个宏定义在board/xinna2440/config.mk中，默认是0x33f80000*/
    mov r1, #0x0  /*从nandflash的0地址读取*/
    mov r2, #0x30000  /*读取长度*/

    bl nand_read_ll    /*开始循环读取*/
    tst r0, #0x0  /*判断函数返回值*/
    beq ok_nand_read

bad_nand_read:
    loop2: b loop2  /*读取出错，死循环*/

ok_nand_read:
    mov r0,#0
    ldr r1,=TEXT_BASE
    mov r2,#0x400
        /*读取成功，以下代码用于校验内存数据和sram中的数据是否一样*/

go_next:
    ldr r3, [r0], #4
    ldr r4, [r1], #4
    teq r3, r4
    bne notmatch
    subs r2, r2, #4
    beq stack_setup
    bne go_next

notmatch:    /*数据不一致，死循环*/
    loop3: b loop3           /* infinite loop */

至此，我们添加了从nandflash启动u-boot的代码，我们在后面添加一个点灯代码，点亮led1和led2。

loo:
    ldr r4,=0x56000010
    ldr r5,=( 1 << 10) | (1 << 12)
    str r5,[r4]
 
    ldr r4,=0x56000014
    ldr r5,=~(( 1 << 5) | ( 1 << 6))
    str r5,[r4]
    b loo

 烧到板子跑，发现led1和led2并没有像我们所预期的被点亮，是什么原因呢？下回分解!