U-Boot启动分析C语言部分（三）

jarodwang

                书接上回，我们依次来看看init_sequence[]数组当中的各个元素。

首先是cpu_init()函数，定义于lib_arm/arm920t/cpu.c第88行。

接下来的board_init()函数定义于board/smdk2410/smdk2410.c第68行：
int board_init (void)
{
    DECLARE_GLOBAL_DATA_PTR;
    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;
}
interrupt_init()函数定义于cpu/arm920t/s3c24x0/interrupts.c第55行：
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);
}
               
               

本文来自ChinaUnix博客，如果查看原文请点：http://blog.chinaunix.net/u/5192/showart_247608.html