从零开始uboot—实现(6)

操作系统：ubuntu10.04


前言：
    在上一章节中，分析了实现的思路。下面就是实现的源码，在源码中有详细的注释。
1,start.S

/* watch dog registers */
#define    WTCON                        0x53000000


/* clock register */
#define CLKDIVN                        0x4C000014
#define MPLLCON                        0x4C000004
#define S3C2440_MPLL_200MHZ        ((0x5c<<12)|(0x01<<4)|(0x02))
#define S3C2440_MPLL_400MHZ ((0x5c<<12)|(0x01<<4)|(0x01))


/* sdram */
#define MEM_CTL_BASE                0x48000000


.text
.global    _start
_start:

/* 1. 关闭看门狗 */
    ldr r0, =WTCON
    mov r1, #0
    str r1, [r0]


/* 2. 设置时钟 */
    ldr r0, =CLKDIVN
    //mov r1, #0x03;            // FCLK:HCLK:PCLK=1:2:4, HDIVN=1,PDIVN=1
    mov r1, #0x05;              // FCLK:HCLK:PCLK=1:4:8
    str r1, [r0]

    /* 如果HDIVN非0，CPU的总线模式应该从“fast bus mode”变为“asynchronous bus mode” */
    mrc        p15, 0, r1, c1, c0, 0        /* 读出控制寄存器 */
    orr        r1,    r1, #0xc0000000            /* 设置为“asynchronous bus mode” */
    mcr        p15, 0, r1, c1, c0, 0        /* 写入控制寄存器 */

    /* MPLLCON = S3C2440_MPLL_200MHZ */
    ldr    r0, =MPLLCON
    //ldr r1, =S3C2440_MPLL_200MHZ
    ldr r1, =S3C2440_MPLL_400MHZ
    str r1, [r0]

    /* 启动ICACHE */
    mrc p15, 0, r0, c1, c0, 0    @ read control reg
    orr r0, r0, #(1<<12)
    mcr    p15, 0, r0, c1, c0, 0   @ write it back


/* 3. 初始化 SDRAM */
    ldr r0, =MEM_CTL_BASE
    adr r1, sdram_config
    add r3, r0, #(13*4)

1:
    ldr r2, [r1], #4
    str r2, [r0], #4
    cmp r0, r3
    bne    1b


/* 4. 重定位:把 bootloader 本身的代码从flash中复制到对应的内存的链接地址中*/
    ldr sp,    =0x34000000        /* 64M SDRAM ,设置栈指针，栈是向下生长，故指向邋邋錝DRAM的最高处*/

    bl nand_init            /* 初始化 NAND FLASH */

    mov r0, #0                /* src执行0地址。当为NAND FLASH 启动时，src指向的是邋錍PU片内内存的地址0.
                               当 NOR FLASH 启动时，src指向的是NOR FLASH 的地址0*/
    ldr r1, =_start            /* dest地址，为 *.lds 中定义的起始地址，此处为 0x33f80000*/
    ldr r2, =__bss_start    /* bss 段的起始地址*/
    sub r2, r2, r1            /* r2 - r1,表示这个*.bin 文件的大小*/
    bl    copy_code_to_sdram

    bl     clear_bss             /* 清空 sdram 中 *.bin文件的bss段内存地址*/


/* 5. 跳转到第二部分代码中执行*/
    ldr lr, =halt            /* 当 main 函数返回时，执行 halt 代码*/
    ldr pc, =main


halt:                        /* 死循环 */
    b    halt



sdram_config:
    .long 0x22011110     //BWSCON
    .long 0x00000700     //BANKCON0
    .long 0x00000700     //BANKCON1
    .long 0x00000700     //BANKCON2
    .long 0x00000700     //BANKCON3
    .long 0x00000700     //BANKCON4
    .long 0x00000700     //BANKCON5
    .long 0x00018005     //BANKCON6
    .long 0x00018005     //BANKCON7
    .long 0x008C04F4     // REFRESH
    .long 0x000000B1     //BANKSIZE
    .long 0x00000030     //MRSRB6
    .long 0x00000030     //MRSRB7

2,boot.lds

SECTIONS {
    . = 0x33f80000;
    .text : { *(.text) }

    . = ALIGN(4);
    .rodata : {*(.rodata)}

    . = ALIGN(4);
    .data : { *(.data) }

    . = ALIGN(4);
    __bss_start = .;
    .bss : { *(.bss) *(COMMON) }
    __bss_end = .;
}

3,init.c
点击(此处)折叠或打开

/* nand flash */
#define NFCONF                         (*((volatile unsigned long *)0x4E000000))
#define NFCONT                         (*((volatile unsigned long *)0x4E000004))
#define NFCMMD                        (*((volatile unsigned char *)0x4E000008))
#define NFADDR                        (*((volatile unsigned char *)0x4E00000C))
#define NFDATA                        (*((volatile unsigned char *)0x4E000010))
#define NFSTAT                        (*((volatile unsigned char *)0x4E000020))


/* gpio */
#define GPHCON                        (*((volatile unsigned long *)0x56000070))
#define GPHUP                        (*((volatile unsigned long *)0x56000078))


/* uart registers*/
#define ULCON0                        (*((volatile unsigned long *)0x50000000))
#define UCON0                        (*((volatile unsigned long *)0x50000004))
#define UFCON0                        (*((volatile unsigned long *)0x50000008))
#define UMCON0                        (*((volatile unsigned long *)0x5000000c))
#define UTRSTAT0                    (*((volatile unsigned long *)0x50000010))
#define UTXH0                        (*((volatile unsigned long *)0x50000020))
#define URXH0                        (*((volatile unsigned long *)0x50000024))
#define UBRDIV0                        (*((volatile unsigned long *)0x50000028))


void nand_read(unsigned int addr, unsigned char *buf, unsigned int len);
void nand_addr(unsigned int addr);

void        nand_init(void)
{
#define    TACLS        0
#define    TWRPH0        1
#define    TWRPH1        0

    /* 设置时钟*/
    NFCONF    = (TACLS<<12) | (TWRPH0<<8) | (TWRPH1<<4) ;
    /* 使能NAND FLASH 控制器，初始化ECC，禁止片选*/
    NFCONT      = (1<<4) | (1<<1) | (1<<0);
}


static void        nand_select(void)
{
    NFCONT &= ~(1<<1);
}


static void        nand_deselect(void)
{
    NFCONT |= (1<<1);
}


static void        nand_cmd(unsigned char cmd)
{
    volatile     char i = 0;
    NFCMMD = cmd;
    for( i = 0; i < 10; i++) ;    /* 稍微延时，确保命令正确写入*/
}


static void        nand_wait_ready(void)
{
    while(!(NFSTAT & 0x01)) ;
}


static unsigned char nand_data(void)
{
    return NFDATA;
}


void    nand_addr(unsigned int addr)
{

    unsigned int col = addr % 2048;
    unsigned int page = addr / 2048;
    volatile int i;


    /* 写一个地址，需要分成五个步骤*/
    /* 先写入两个列地址*/
    NFADDR = col & 0xff;
    for    (i = 0; i < 10; i++);
    NFADDR = (col >> 8) & 0xff;
    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) & 0xff;
    for (i = 0; i < 10; i++);
}



void        nand_read(unsigned int addr, unsigned char * buffer,unsigned int len)
{
    int    col    = addr % 2048;
    int    i     = 0;

    /* 1 选中*/
    nand_select();

    while(i < len)
    {
        /* 2 发出读命令00h */
        nand_cmd(0x00);

        /* 3 发出地址(分5 步发出) */
        nand_addr(addr);

        /* 4 发出读命令30h */
        nand_cmd(0x30);

        /* 5 判断状态*/
        nand_wait_ready();

        /* 6 读数据*/
        /* 当前NAND FLASH 是以2k为一页的*/
        /* 每次读取一页数据到对应寄存器中*/
        for( ; (col < 2048) && ( i < len) ; col++ )
        {
            buffer[i] = nand_data();
            i++;
            addr++;
        }
        col = 0;            /* 如果数据分布在不同的页中，则读取下一页时，从第0列开始读取*/
    }

    /* 7 取消选中*/
    nand_deselect();
}


#if 1
int         isBootFromNorFlash(void)
{
    volatile int *p = (volatile int*)0;
    int val = 0;

    val = *p;
    *p = 0x12345678;        /* Nor Flash 中是不允许写入数据的*/

    if(0x12345678 == *p)
    {
        /* 写成功，是NAND FLASH */
        *p = val;
        return 0;
    }
    else
    {
        /* NOR FLASH 不能像内存一样写*/
        return 1;
    }
}



void     copy_code_to_sdram(unsigned char *src, unsigned char *dest, unsigned int len)
{
    int i = 0;

    if(isBootFromNorFlash())
    {
        /* NOR FLASH 中的数据可以像内存中的数据那样，直接读取*/
        while( i < len )
        {
            dest[i] = src[i];
            i++;
        }
    }
    else
    {
        /* NAND FLASH*/
        nand_read((unsigned int )src, dest, len);
    }
}

#endif

void     clear_bss(void)
{
    extern    int    __bss_start,__bss_end;
    int *p = &__bss_start;

    for( ; p < &__bss_end; p++)
        *p = 0;
}




#define    PCLK        50000000        /* start.S 中把时钟设置PCLK为50MHz*/
#define    UART_CLK    PCLK            /* UART0的时钟源设为PCLK */
#define    UART_BAUD_RATE    115200    /* 波特率为115200*/
#define    UART_BRD    ((UART_CLK / (UART_BAUD_RATE * 16)) - 1)

void        uart0_init(void)
{
    GPHCON        |=     0xa0;            /* GPH2,GPH3用作TXD0,RXD0 */
    GPHUP        =     0x0C;            /* GPH2,GPH3 内部上拉*/

    ULCON0        =     0x03;            /* 8N1(8个数据位，无较验，1个停止位) */
    UCON0        =     0x05;            /* 查询方式，UART时钟源为PCLK */
    UFCON0        =     0x00;            /* 不使用FIFO */
    UMCON0        =     0x00;            /* 不使用流控制*/
    UBRDIV0        =     UART_BRD;        /* 波特率为115200 */
}



#define TXD0READY (1<<2)

void        putc(unsigned char c)
{
    /* 等待，直到发送缓冲区中的数据已经全部发送出去 */
    while(!(UTRSTAT0 & TXD0READY)) ;

    /* 向UTXH0寄存器中写入数据，UART即自动将它发送出去 */
     UTXH0    = c;
}



void        puts(char * str)
{
    int    i = 0;
    while(str[i])
    {
        putc(str[i]);
        ++i;
    }
}

4,boot.c

#include "setup.h"

extern    void        uart0_init(void);
extern    void        nand_read(unsigned int addr, unsigned char * buffer,unsigned int len);
extern    void        puts(char * str);



int strlen(char *str)
{
    int i = 0;
    while (str[i])
    {
        i++;
    }
    return i;
}

void strcpy(char *dest, char *src)
{
    while ((*dest++ = *src++) != '\0');
}


static struct tag *params;

void setup_start_tag(void)
{
    params = (struct tag *)0x30000100;    /* 内核约定存放在这个地方*/

    params->hdr.tag = ATAG_CORE;
    params->hdr.size = tag_size (tag_core);

    params->u.core.flags = 0;
    params->u.core.pagesize = 0;
    params->u.core.rootdev = 0;

    params = tag_next (params);
}


void setup_memory_tags(void)
{
    params->hdr.tag = ATAG_MEM;
    params->hdr.size = tag_size (tag_mem32);

    params->u.mem.start = 0x30000000;    /* SDRAM起始地址*/
    params->u.mem.size = 64*1024*1024;    /* 其大小为64 M */

    params = tag_next (params);
}


void setup_commandline_tag(char *cmdline)
{
    int len = strlen(cmdline) + 1;

    params->hdr.tag = ATAG_CMDLINE;

    /* 以4 个字节对齐，并且以4个字节为单位*/
    params->hdr.size = (sizeof (struct tag_header) + len + 3) >> 2;

    strcpy (params->u.cmdline.cmdline, cmdline);

    params = tag_next (params);
}


void setup_end_tag(void)
{
    params->hdr.tag = ATAG_NONE;
    params->hdr.size = 0;
}


int main(void)
{
    /* 函数指针，执行内核的起始位置*/
    void (*theKernel)(int zero, int arch, unsigned int params);

    /* 1 帮内核设置串口: 内核启动的开始部分会从串口打印一些信息,但是内核一开始没有初始化串口*/
    uart0_init();

    /* 2 从NAND FLASH 中把内核读入到内存中*/
    puts("Copy kernel from nand\n\r");
    /* 内核存放在NAND FLASH 中的0x60000 地址。
         存放的是uImage，该文件包含64 字节的头部信息。
         内核一般都存放在0x30008000这个地址，除非手动修改内核。*/
    nand_read(0x60000+64,( unsigned char * )0x30008000, 0x200000);

    /* 3 设置引导内核的参数*/
    puts("Set boot params\n\r");
    setup_start_tag();
    setup_memory_tags();    /*内核大小*/
    setup_commandline_tag("noinitrd root=/dev/mtdblock3 init=/linuxrc console=ttySAC0");    /* 命令参数*/
    setup_end_tag();

    /* 4 跳转执行*/
    puts("Boot kernel\n\r");
    theKernel = (void (*)(int ,int ,unsigned int))0x30008000; /* 真正的内核起始地址*/
    /*     参数1 : 默认为0.
        参数2 : 为machine ID,当前设置为362。可在内核源码中: arch/arm/tools/mach_types 修改。
        参数3 : 为参数的起始地址(params)*/
    theKernel(0,362,0x30000100);

    /* 5 异常:如果正确引导内核，不应该执行到这里*/
    puts("Error!\n\r");
    return -1;
}

5,setup.h
    该文件是直接从uboot中复制过来的。

/*
 * linux/include/asm/setup.h
 *
 * Copyright (C) 1997-1999 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Structure passed to kernel to tell it about the
 * hardware it's running on. See linux/Documentation/arm/Setup
 * for more info.
 *
 * NOTE:
 * This file contains two ways to pass information from the boot
 * loader to the kernel. The old struct param_struct is deprecated,
 * but it will be kept in the kernel for 5 years from now
 * (2001). This will allow boot loaders to convert to the new struct
 * tag way.
 */
#ifndef __ASMARM_SETUP_H
#define __ASMARM_SETUP_H

#define u8  unsigned char
#define u16 unsigned short
#define u32 unsigned long

/*
 * Usage:
 * - do not go blindly adding fields, add them at the end
 * - when adding fields, don't rely on the address until
 * a patch from me has been released
 * - unused fields should be zero (for future expansion)
 * - this structure is relatively short-lived - only
 * guaranteed to contain useful data in setup_arch()
 */
#define COMMAND_LINE_SIZE 1024

/* This is the old deprecated way to pass parameters to the kernel */
struct param_struct {
    union {
    struct {
        unsigned long page_size;        /* 0 */
        unsigned long nr_pages;        /* 4 */
        unsigned long ramdisk_size;        /* 8 */
        unsigned long flags;        /* 12 */
#define FLAG_READONLY    1
#define FLAG_RDLOAD    4
#define FLAG_RDPROMPT    8
        unsigned long rootdev;        /* 16 */
        unsigned long video_num_cols;    /* 20 */
        unsigned long video_num_rows;    /* 24 */
        unsigned long video_x;        /* 28 */
        unsigned long video_y;        /* 32 */
        unsigned long memc_control_reg;    /* 36 */
        unsigned char sounddefault;        /* 40 */
        unsigned char adfsdrives;        /* 41 */
        unsigned char bytes_per_char_h;    /* 42 */
        unsigned char bytes_per_char_v;    /* 43 */
        unsigned long pages_in_bank[4];    /* 44 */
        unsigned long pages_in_vram;    /* 60 */
        unsigned long initrd_start;        /* 64 */
        unsigned long initrd_size;        /* 68 */
        unsigned long rd_start;        /* 72 */
        unsigned long system_rev;        /* 76 */
        unsigned long system_serial_low;    /* 80 */
        unsigned long system_serial_high;    /* 84 */
        unsigned long mem_fclk_21285; /* 88 */
    } s;
    char unused[256];
    } u1;
    union {
    char paths[8][128];
    struct {
        unsigned long magic;
        char n[1024 - sizeof(unsigned long)];
    } s;
    } u2;
    char commandline[COMMAND_LINE_SIZE];
};


/*
 * The new way of passing information: a list of tagged entries
 */

/* The list ends with an ATAG_NONE node. */
#define ATAG_NONE    0x00000000

struct tag_header {
    u32 size;
    u32 tag;
};

/* The list must start with an ATAG_CORE node */
#define ATAG_CORE    0x54410001

struct tag_core {
    u32 flags;        /* bit 0 = read-only */
    u32 pagesize;
    u32 rootdev;
};

/* it is allowed to have multiple ATAG_MEM nodes */
#define ATAG_MEM    0x54410002

struct tag_mem32 {
    u32    size;
    u32    start;    /* physical start address */
};

/* VGA text type displays */
#define ATAG_VIDEOTEXT    0x54410003

struct tag_videotext {
    u8        x;
    u8        y;
    u16        video_page;
    u8        video_mode;
    u8        video_cols;
    u16        video_ega_bx;
    u8        video_lines;
    u8        video_isvga;
    u16        video_points;
};

/* describes how the ramdisk will be used in kernel */
#define ATAG_RAMDISK    0x54410004

struct tag_ramdisk {
    u32 flags;    /* bit 0 = load, bit 1 = prompt */
    u32 size;    /* decompressed ramdisk size in _kilo_ bytes */
    u32 start;    /* starting block of floppy-based RAM disk image */
};

/* describes where the compressed ramdisk image lives (virtual address) */
/*
 * this one accidentally used virtual addresses - as such,
 * its depreciated.
 */
#define ATAG_INITRD    0x54410005

/* describes where the compressed ramdisk image lives (physical address) */
#define ATAG_INITRD2    0x54420005

struct tag_initrd {
    u32 start;    /* physical start address */
    u32 size;    /* size of compressed ramdisk image in bytes */
};

/* board serial number. "64 bits should be enough for everybody" */
#define ATAG_SERIAL    0x54410006

struct tag_serialnr {
    u32 low;
    u32 high;
};

/* board revision */
#define ATAG_REVISION    0x54410007

struct tag_revision {
    u32 rev;
};

/* initial values for vesafb-type framebuffers. see struct screen_info
 * in include/linux/tty.h
 */
#define ATAG_VIDEOLFB    0x54410008

struct tag_videolfb {
    u16        lfb_width;
    u16        lfb_height;
    u16        lfb_depth;
    u16        lfb_linelength;
    u32        lfb_base;
    u32        lfb_size;
    u8        red_size;
    u8        red_pos;
    u8        green_size;
    u8        green_pos;
    u8        blue_size;
    u8        blue_pos;
    u8        rsvd_size;
    u8        rsvd_pos;
};

/* command line: \0 terminated string */
#define ATAG_CMDLINE    0x54410009

struct tag_cmdline {
    char    cmdline[1];    /* this is the minimum size */
};

/* acorn RiscPC specific information */
#define ATAG_ACORN    0x41000101

struct tag_acorn {
    u32 memc_control_reg;
    u32 vram_pages;
    u8 sounddefault;
    u8 adfsdrives;
};

/* footbridge memory clock, see arch/arm/mach-footbridge/arch.c */
#define ATAG_MEMCLK    0x41000402

struct tag_memclk {
    u32 fmemclk;
};

struct tag {
    struct tag_header hdr;
    union {
        struct tag_core        core;
        struct tag_mem32    mem;
        struct tag_videotext    videotext;
        struct tag_ramdisk    ramdisk;
        struct tag_initrd    initrd;
        struct tag_serialnr    serialnr;
        struct tag_revision    revision;
        struct tag_videolfb    videolfb;
        struct tag_cmdline    cmdline;

        /*
         * Acorn specific
         */
        struct tag_acorn    acorn;

        /*
         * DC21285 specific
         */
        struct tag_memclk    memclk;
    } u;
};

struct tagtable {
    u32 tag;
    int (*parse)(const struct tag *);
};


#define tag_member_present(tag,member)                \
    ((unsigned long)(&((struct tag *)0L)->member + 1)    \
        <= (tag)->hdr.size * 4)

#define tag_next(t)    ((struct tag *)((u32 *)(t) + (t)->hdr.size))
#define tag_size(type)    ((sizeof(struct tag_header) + sizeof(struct type)) >> 2)

#define for_each_tag(t,base)        \
    for (t = base; t->hdr.size; t = tag_next(t))

/*
 * Memory map description
 */
#define NR_BANKS 8

struct meminfo {
    int nr_banks;
    unsigned long end;
    struct {
        unsigned long start;
        unsigned long size;
        int node;
    } bank[NR_BANKS];
};

extern struct meminfo meminfo;

#endif

6,Makefile

CC = arm-linux-gcc
LD = arm-linux-ld
AR = arm-linux-ar
OBJCOPY = arm-linux-objcopy
OBJDUMP = arm-linux-objdump

CFLAGS         := -Wall -O2
CPPFLAGS       := -nostdinc -nostdlib -fno-builtin

objs := start.o init.o boot.o

boot.bin: $(objs)
    ${LD} -Tboot.lds -o boot.elf $^
    ${OBJCOPY} -O binary -S boot.elf $@
    ${OBJDUMP} -D -m arm boot.elf > boot.dis

%.o:%.c
    ${CC} $(CPPFLAGS) $(CFLAGS) -c -o $@ $<

%.o:%.S
    ${CC} $(CPPFLAGS) $(CFLAGS) -c -o $@ $<

clean:
    rm -f *.o *.bin *.elf *.dis

7,总结
   至此，从零开始实现的uboot基本完成。