init_sequence所对应的函数

一、init_sequence内容

init_fnc_t *init_sequence[] = {
    cpu_init,        /* basic cpu dependent setup */
    board_init,        /* basic board dependent setup */
    interrupt_init,        /* set up exceptions */
    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
    dram_init,        /* configure available RAM banks */
    display_dram_config,
    NULL,
};

二、cpu_init（cpu/arm920t/cpu.c）

int cpu_init (void)
{
    /*
     * setup up stacks if necessary
     */
#ifdef CONFIG_USE_IRQ
    IRQ_STACK_START = _armboot_start - CFG_MALLOC_LEN - CFG_GBL_DATA_SIZE - 4;
    FIQ_STACK_START = IRQ_STACK_START - CONFIG_STACKSIZE_IRQ;
#endif
    return 0;
} 

三、board_init（board/smdk2410/smdk2410.c）

int board_init (void)
{
    S3C24X0_CLOCK_POWER * const clk_power = S3C24X0_GetBase_CLOCK_POWER();
    S3C24X0_GPIO * const gpio = S3C24X0_GetBase_GPIO();

    /* to reduce PLL lock time, adjust the LOCKTIME register */
    clk_power->LOCKTIME = 0xFFFFFF;

    /* configure MPLL */
    clk_power->MPLLCON = ((M_MDIV << 12) + (M_PDIV << 4) + M_SDIV);

    /* some delay between MPLL and UPLL */
    delay (4000);

    /* configure UPLL */
    clk_power->UPLLCON = ((U_M_MDIV << 12) + (U_M_PDIV << 4) + U_M_SDIV);

    /* some delay between MPLL and UPLL */
    delay (8000);

    /* 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;

    /* arch number of SMDK2410-Board */
    gd->bd->bi_arch_number = MACH_TYPE_SMDK2410;

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

    icache_enable();
    dcache_enable();

    return 0;
}

四、interrupt_init（cpu/arm920t/s3c24x0.c）

int interrupt_init (void)
{
    S3C24X0_TIMERS * const timers = S3C24X0_GetBase_TIMERS();

    /* use PWM Timer 4 because it has no output */
    /* prescaler for Timer 4 is 16 */
    timers->TCFG0 = 0x0f00;
    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);
    }
    /* load value for 10 ms timeout */
    lastdec = timers->TCNTB4 = timer_load_val;
    /* auto load, manual update of Timer 4 */
    timers->TCON = (timers->TCON & ~0x0700000) | 0x600000;
    /* auto load, start Timer 4 */
    timers->TCON = (timers->TCON & ~0x0700000) | 0x500000;
    timestamp = 0;

    return (0);
}

五、env_init

    uboot支持把环境变量放在很多存储器上，例如norflash、nandflash、eeprom等等，不同的方式env_init函数的实现也是不同的，但是env_init函数最终会被start_amboot调用，屏蔽了这些差异。

smdk2410.h中默认选择的是norflash：
include/configs/smdk2410.h
#define    CFG_ENV_IS_IN_FLASH    1

（common/Env_flash.c）

#ifdef CFG_ENV_ADDR_REDUND //未被定义

int  env_init(void)
{
#ifdef CONFIG_OMAP2420H4
    int flash_probe(void);

    if(flash_probe() == 0)
        goto bad_flash;
#endif
    if (crc32(0, env_ptr->data, ENV_SIZE) == env_ptr->crc) {
        gd->env_addr  = (ulong)&(env_ptr->data);
        gd->env_valid = 1;
        return(0);
    }
#ifdef CONFIG_OMAP2420H4
bad_flash:
#endif
    gd->env_addr  = (ulong)&default_environment[0];
    gd->env_valid = 0;
    return (0);
}

六、init_baudrate（lib_arm/board.c）

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);
}

七、serial_init（cpu/arm920t/s3c24x0/serial.c）

int serial_init (void)
{
    serial_setbrg ();

    return (0);
}
void serial_setbrg (void)
{
    S3C24X0_UART * const uart = S3C24X0_GetBase_UART(UART_NR);
    int i;
    unsigned int reg = 0;

    /* value is calculated so : (int)(PCLK/16./baudrate) -1 */
    reg = get_PCLK() / (16 * gd->baudrate) - 1;

    /* FIFO enable, Tx/Rx FIFO clear */
    uart->UFCON = 0x07;
    uart->UMCON = 0x0;
    /* Normal,No parity,1 stop,8 bit */
    uart->ULCON = 0x3;
    /*
     * tx=level,rx=edge,disable timeout int.,enable rx error int.,
     * normal,interrupt or polling
     */
    uart->UCON = 0x245;
    uart->UBRDIV = reg;

#ifdef CONFIG_HWFLOW
    uart->UMCON = 0x1; /* RTS up */
#endif
    for (i = 0; i < 100; i++);
}

八、console_init_f（common/console.c）

/* Called before relocation - use serial functions */
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);
}

九、display_banner（lib_arm/board.c）

static int display_banner (void)
{
    printf ("

%s

", version_string);
    debug ("U-Boot code: %08lX -> %08lX  BSS: -> %08lX
",
           _armboot_start, _bss_start, _bss_end);
#ifdef CONFIG_MODEM_SUPPORT
    debug ("Modem Support enabled
");
#endif
#ifdef CONFIG_USE_IRQ
    debug ("IRQ Stack: %08lx
", IRQ_STACK_START);
    debug ("FIQ Stack: %08lx
", FIQ_STACK_START);
#endif

    return (0);
}

十、dram_init（board/smdk2410.c）

int dram_init (void)
{
    gd->bd->bi_dram[0].start = PHYS_SDRAM_1;
    gd->bd->bi_dram[0].size = PHYS_SDRAM_1_SIZE;

    return 0;
}

十、display_dram_config （lib_arm/board.c）

static int display_dram_config (void)
{
    int i;

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

    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, "
");
    }
#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, "
");
#endif

    return (0);
}