UBOOT-2010.06分析 第二段C_code

bootloader启动代码start.s调用
ldr    pc ，_start_armboot
_start_armboot :  .word start_armboot
将_start_armboot地址的内容start_armboot赋给pc从而进入第二阶段

---

第二阶段的功能：
<1>初始化IRQ FIQ模式的栈
  arch_cpu_init
<2>设置系统时钟 保存机器ID

gd->bd->bi_arch_number = MACH_TYPE_S3C2440;   //值为362
<3>初始化中断、定时器
 interrupt_init
 timer_init
<4>检查flash上的环境参数是否有效
   env_init
<5>初始化串口控制台
 init_baudrate, /* initialze baudrate settings */
   serial_init, /* serial communications setup */
   console_init_f, /* stage 1 init of console */
<6> say that we are here 打印出uboot的版本信息及各模块的地址

   display_banner
<7>检测系统内存映射（memory map）

int dram_init(void)

{config配置中有关于 PHYS_SDRAM_1 PHYS_SDRAM_1_SIZE变量的定义

     gd->bd->bi_dram[0] . start = PHYS_SDRAM_1;          //即0x3000 0000

     gd->bd->bi_dram[0].size = PHYS_SDRAM_1_SIZE;  //即0x0400 0000

}
<8>将SDRAM的参数打印出来
  display_dram_config

<9>初始化NOR_flash并打印出其配置的参数数信息
  display_flash_config (flash_init ());

10>Nand_flash初始化
   nand_init()
<11>初始化环境变量并读入指定的内存
   env_relocate ();

<12>初始化各种设备驱动 i2c lcd key等
  stdio_init (); /* get the devices list going. */

<13>初始化网络设备 和控制台 使能中断
  gd->bd->bi_ip_addr = getenv_IPaddr ("ipaddr");

   console_init_r (); /* fully init console as a device */

---

代码分析：
start_armboot()
{ 

init_fnc_t **init_fnc_ptr;       //定义二级函数指针
 char *s;
 gd = (gd_t*)(_armboot_start - CONFIG_SYS_MALLOC_LEN - sizeof(gd_t));

定义了全局数据指针，armboot_start的值位于0x3ff80000,且CONFIG_SYS_MALLOC_LEN在congfig中有定义

#define config_sys_malloc_len  (CONFIG_ENV_SIZE + 128 * 1024)

#define CONFIG_ENV_SIZE  0x20000   //128K为256M的Nandflash的块大小，block。

通过以上计算得出 config_sys_malloc_len 的大小为 256k = 0x4 0000。

再来看一下结构体gd_t,位于arch/arm/include/asm/global_data.h

sizeof(gd_t)=4 + 4 * 6 + 4+？+？ = 32 +?= 0x20+?。

故gd所指向地址 0x3ff80000 - 0x40000 -  0x20-?为 0x3FF3 FFE0-?

typedef    struct    global_data {
    bd_t        *bd;
    unsigned long    flags;
    unsigned long    baudrate;
    unsigned long    have_console;    /* serial_init() was called */
    unsigned long    env_addr;    /* Address  of Environment struct */
    unsigned long    env_valid;    /* Checksum of Environment valid? */
    unsigned long    fb_base;    /* base address of frame buffer */
#ifdef CONFIG_VFD
    unsigned char    vfd_type;    /* display type */
#endif
#ifdef CONFIG_FSL_ESDHC
    unsigned long    sdhc_clk;
#endif
#if 0
    unsigned long    cpu_clk;    /* CPU clock in         */
    unsigned long    bus_clk;
    phys_size_t    ram_size;    /* RAM size */
    unsigned long    reset_status;    /* reset status register at boot */
#endif
    void        **jt;        /* jump table */
} gd_t;
/*
 * Global Data Flags
 */
#define    GD_FLG_RELOC    0x00001        /* Code was relocated to RAM        */
#define    GD_FLG_DEVINIT    0x00002        /* Devices have been initialized    */
#define    GD_FLG_SILENT    0x00004        /* Silent mode                */
#define    GD_FLG_POSTFAIL    0x00008        /* Critical POST test failed        */
#define    GD_FLG_POSTSTOP    0x00010        /* POST seqeunce aborted        */
#define    GD_FLG_LOGINIT    0x00020        /* Log Buffer has been initialized    */
#define GD_FLG_DISABLE_CONSOLE    0x00040        /* Disable console (in & out)     */

#define DECLARE_GLOBAL_DATA_PTR     register volatile gd_t *gd asm
typedef struct bd_info {
    int            bi_baudrate;    /* serial console baudrate */
    unsigned long    bi_ip_addr;    /* IP Address */
    struct environment_s     *bi_env;
    ulong            bi_arch_number;    /* unique id for this board */
    ulong            bi_boot_params;    /* where this board expects params */
    struct                /* RAM configuration */
    {
    ulong start;
    ulong size;
    }            bi_dram[CONFIG_NR_DRAM_BANKS];
} bd_t;

__asm__ __volatile__("": : :"memory"); //分配一个存储全局数据的区域，地址给指针 gd/

memset ((void*)gd, 0, sizeof (gd_t));//给全局变量gd初始化
gd->bd = (bd_t*)((char*)gd - sizeof(bd_t));
memset (gd->bd, 0, sizeof (bd_t));//变量bd初始化
gd->flags |= GD_FLG_RELOC; /* Code was relocated to RAM  在初始化波特率时会用到 根据此标志来找到波特率等环境变量存放的位置*/

//uboot镜像文件大小

monitor_flash_len = _bss_start - _armboot_start;

//初始化函数循环
 见上述<3>--<8>

for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
       if ((*init_fnc_ptr)() != 0)

      {
           hang ();
      }
 }

typedef int (init_fnc_t) (void);

int print_cpuinfo (void);

init_fnc_t *init_sequence[] = {
#if defined(CONFIG_ARCH_CPU_INIT)
    arch_cpu_init,        /* basic arch cpu dependent setup */
#endif
    board_init,        /* basic board dependent setup */
#if defined(CONFIG_USE_IRQ)
    interrupt_init,        /* set up exceptions */
#endif
    timer_init,        /* initialize timer */
#ifdef CONFIG_FSL_ESDHC
    get_clocks,
#endif
    env_init,        /* initialize environment */
    init_baudrate,        /* initialze baudrate settings */
    serial_init,        /* serial communications setup */
    console_init_f,        /* stage 1 init of console */
    display_banner,        /* say that we are here */
#if defined(CONFIG_DISPLAY_CPUINFO)
    print_cpuinfo,        /* display cpu info (and speed) */
#endif
#if defined(CONFIG_DISPLAY_BOARDINFO)
    checkboard,        /* display board info */
#endif
#if defined(CONFIG_HARD_I2C) || defined(CONFIG_SOFT_I2C)
    init_func_i2c,
#endif
    dram_init,        /* configure available RAM banks */
#if defined(CONFIG_CMD_PCI) || defined (CONFIG_PCI)
    arm_pci_init,
#endif
    display_dram_config,
    NULL,
};

mem_malloc_init (_armboot_start - CONFIG_SYS_MALLOC_LEN,CONFIG_SYS_MALLOC_LEN);
//堆清0以便下次再用

//下面再是各种初始化

display_flash_config (flash_init ());
nand_init();        /* go init the NAND */

/* initialize environment */
    env_relocate ();
/* IP Address */
    gd->bd->bi_ip_addr = getenv_IPaddr ("ipaddr");

    stdio_init ();    /* get the devices list going. */

    jumptable_init ();
console_init_r ();    /* fully init console as a device
/* enable exceptions */
    enable_interrupts ();

  /*fengpan add begin*/
#ifdef CONFIG_USB_DEVICE
    usb_init_slave();
#endif
eth_initialize(gd->bd);

for (;;) {
      main_loop ();
}

---

初始化循环函数：分析

for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
       if ((*init_fnc_ptr)() != 0)

{   hang ();}}

---

board_init

int board_init (void)
{
    struct s3c24x0_clock_power * const clk_power =
                    s3c24x0_get_base_clock_power();
    struct s3c24x0_gpio * const gpio = s3c24x0_get_base_gpio();

    /* set up the I/O ports
    gpio->GPACON = 0x007FFFFF;
    gpio->GPBCON = 0x00044555;
    gpio->GPBUP = 0x000007FF;
    gpio->GPCCON = 0xAAAAAAAA;
    gpio->GPCUP = 0x0000FFFF;
    gpio->GPDCON = 0xAAAAAAAA;
    gpio->GPDUP = 0x0000FFFF;
    gpio->GPECON = 0xAAAAAAAA;
    gpio->GPEUP = 0x0000FFFF;
    gpio->GPFCON = 0x000055AA;
    gpio->GPFUP = 0x000000FF;
    gpio->GPGCON = 0xFF95FFBA;
    gpio->GPGUP = 0x0000FFFF;
    gpio->GPHCON = 0x002AFAAA;
    gpio->GPHUP = 0x000007FF;*/
    /* set up the I/O ports */
    /* support both of S3C2410 and S3C2440, by www.arm9.net */
    if ((gpio->GSTATUS1 == 0x32410000) || (gpio->GSTATUS1 == 0x32410002))
    {
        /* arch number of SMDK2410-Board */
        gd->bd->bi_arch_number = MACH_TYPE_SMDK2410;
    }
    else
    {
        /* arch number of SMDK2440-Board */
        gd->bd->bi_arch_number = MACH_TYPE_S3C2440;
    }

    /* adress of boot parameters */
    gd->bd->bi_boot_params = 0x30000100;

    icache_enable();
    dcache_enable();

    return 0;
}

timer_init, /* initialize timer */

int timer_init(void)
{
    struct s3c24x0_timers *timers = s3c24x0_get_base_timers();
    ulong tmr;

    /* use PWM Timer 4 because it has no output */
    /* prescaler for Timer 4 is 16 */
    writel(0x0f00, &timers->TCFG0);//预分频15+1=16 to timer4
    if (timer_load_val == 0) {
        /*
         * for 10 ms clock period @ PCLK with 4 bit divider = 1/2
         * (default) and prescaler = 16. Should be 10390
         * @33.25MHz and 15625 @ 50 MHz
         */
        timer_load_val = get_PCLK() / (2 * 16 * 100);
        timer_clk = get_PCLK() / (2 * 16);
    }
    /* load value for 10 ms timeout */
    lastdec = timer_load_val;
    writel(timer_load_val, &timers->TCNTB4);
    /* auto load, manual update of Timer 4 */
    tmr = (readl(&timers->TCON) & ~0x0700000) | 0x0600000;
    writel(tmr, &timers->TCON);
    /* auto load, start Timer 4 */
    tmr = (tmr & ~0x0700000) | 0x0500000;
    writel(tmr, &timers->TCON);
    timestamp = 0;

    return (0);
}

int timer_init(void)
{
    struct s3c24x0_timers *timers = s3c24x0_get_base_timers();
    ulong tmr;

    /* use PWM Timer 4 because it has no output */
    /* prescaler for Timer 4 is 16 */
    writel(0x0f00, &timers->TCFG0);
    if (timer_load_val == 0) {
        /*
         * for 10 ms clock period @ PCLK with 4 bit divider = 1/2
         * (default) and prescaler = 16. Should be 10390
         * @33.25MHz and 15625 @ 50 MHz
         */
        timer_load_val = get_PCLK() / (2 * 16 * 100);
        timer_clk = get_PCLK() / (2 * 16);
    }
    /* load value for 10 ms timeout */
    lastdec = timer_load_val;
    writel(timer_load_val, &timers->TCNTB4);
    /* auto load, manual update of Timer 4 */
    tmr = (readl(&timers->TCON) & ~0x0700000) | 0x0600000;
    writel(tmr, &timers->TCON);
    /* auto load, start Timer 4 */
    tmr = (tmr & ~0x0700000) | 0x0500000;
    writel(tmr, &timers->TCON);
    timestamp = 0;

    return (0);
}

env_init, /* initialize environment */

/* this is called before nand_init()
 * so we can't read Nand to validate env data.
 * Mark it OK for now. env_relocate() in env_common.c
 * will call our relocate function which does the real
 * validation.
 *
 * When using a NAND boot image (like sequoia_nand), the environment
 * can be embedded or attached to the U-Boot image in NAND flash. This way
 * the SPL loads not only the U-Boot image from NAND but also the
 * environment.
 */
int env_init(void)
{//在有一部分宏没定义 经过分析 发现此函数实质就执行下面语句
    gd->env_addr = (ulong)&default_environment[0];
    gd->env_valid = 1;//在下面initialze baudrate settings会用到

    return (0);
}

init_baudrate, /* initialze baudrate settings */

static int init_baudrate (void)
{
    char tmp[64];    /* long enough for environment variables */
    int i = getenv_r ("baudrate", tmp, sizeof (tmp));
    gd->bd->bi_baudrate = gd->baudrate = (i > 0)
            ? (int) simple_strtoul (tmp, NULL, 10)
            : CONFIG_BAUDRATE;

    return (0);
}

serial_init, /* serial communications setup */

int serial_init(void)
{
    return serial_init_dev(UART_NR);
}

#ifdef CONFIG_SERIAL1
#define UART_NR	S3C24X0_UART0
static int serial_init_dev(const int dev_index)
{
    struct s3c24x0_uart *uart = s3c24x0_get_base_uart(dev_index);

    /* FIFO enable, Tx/Rx FIFO clear */
    writel(0x07, &uart->UFCON);
    writel(0x0, &uart->UMCON);

    /* Normal,No parity,1 stop,8 bit */
    writel(0x3, &uart->ULCON);
    /*
     * tx=level,rx=edge,disable timeout int.,enable rx error int.,
     * normal,interrupt or polling
     */
    writel(0x245, &uart->UCON);

    /* FIXME: This is sooooooooooooooooooo ugly */
    _serial_setbrg(dev_index);

    return (0);
}

console_init_f, /* stage 1 init of console */

int console_init_f(void)
{
    gd->have_console = 1;

#ifdef CONFIG_SILENT_CONSOLE
    if (getenv("silent") != NULL)
        gd->flags |= GD_FLG_SILENT;
#endif

    return 0;
}

display_banner, /* say that we are here */
//测试串口 以及输出一些初始化后的信息

static int display_banner (void)
{
    printf ("\n\n%s\n\n", version_string);
    debug ("U-Boot code: %08lX -> %08lX  BSS: -> %08lX\n",
           _armboot_start, _bss_start, _bss_end);
#ifdef CONFIG_MODEM_SUPPORT
    debug ("Modem Support enabled\n");
#endif
#ifdef CONFIG_USE_IRQ
    debug ("IRQ Stack: %08lx\n", IRQ_STACK_START);
    debug ("FIQ Stack: %08lx\n", FIQ_STACK_START);
#endif

    return (0);
}

dram_init, /* configure available RAM banks */

int dram_init (void)
{//sdram的初始化
    gd->bd->bi_dram[0].start = PHYS_SDRAM_1;//config文件中 定义 SDRAM的起始地址
    gd->bd->bi_dram[0].size = PHYS_SDRAM_1_SIZE;//config文件中定义SDRAM的大小

    return 0;
}

display_dram_config
//显示SDRAM信息

static int display_dram_config (void)
{
    int i;

#ifdef DEBUG
    puts ("RAM Configuration:\n");

    for(i=0; i<CONFIG_NR_DRAM_BANKS; i++) {
        printf ("Bank #%d: %08lx ", i, gd->bd->bi_dram[i].start);
        print_size (gd->bd->bi_dram[i].size, "\n");
    }
#else
    ulong size = 0;

    for (i=0; i<CONFIG_NR_DRAM_BANKS; i++) {
        size += gd->bd->bi_dram[i].size;
    }
    puts("DRAM:  ");
    print_size(size, "\n");
#endif

    return (0);
}