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标题: U-Boot启动分析C语言部分（三） [打印本页]

作者: jarodwang 时间: 2007-02-15 10:40
标题: U-Boot启动分析C语言部分（三）

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);
}

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