U-Boot中reset实现

chenxibing008

U-Boot的复位命令reset通过do_reset函数实现：

arch/arm/lib/reset.c

1. 42 int do_reset(cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
   
2.  43 {
   
3.  44 puts ("resetting ...\n");
   
4.  45
   
5.  46 udelay (50000); /* wait 50 ms */
   
6.  47
   
7.  48 disable_interrupts();
   
8.  49 reset_cpu(0);
   
9.  50
   
10.  51 /*NOTREACHED*/
    
11.  52 return 0;
    
12.  53 }

reset_cpu(0)的函数原型是reset_cpu(ulong)，一般在具体CPU中实现，可采取内狗超时实现复位：

arch/arm/cpu/arm926ejs/at91/reset.c

1. 4 void reset_cpu(ulong ignored)
   
2.   5 {
   
3.   6 at91_rstc_t *rstc = (at91_rstc_t *) AT91_RSTC_BASE;
   
4.   7
   
5.   8 /* this is the way Linux does it */
   
6.   9
   
7.  10 writel(AT91_RSTC_KEY | AT91_RSTC_CR_PROCRST | AT91_RSTC_CR_PERRST,
   
8.  11 &rstc->cr);
   
9.  12
   
10.  13 while (1);
    
11.  14 /* Never reached */
    
12.  15 }

LPC3250的reset_cpu()实现：

arch/arm/cpu/arm926ejs/lpc3250/reset.c

也可以在其它地方实现./board/zhiyuan/m3250evb/m3250evb.c

1. 76 /*
   
2.  77 * Use the watchdog timer to reset the system
   
3.  78 */
   
4.  79 void reset_cpu(ulong addr)
   
5.  80 {
   
6.  81 /* Enable the WDT clock */
   
7.  82 CLKPWR->clkpwr_timer_clk_ctrl |= CLKPWR_PWMCLK_WDOG_EN;
   
8.  83
   
9.  84 /* Instant assert of RESETOUT_N with pulse length 1mS */
   
10.  85 WDT->wdtim_pulse = 13000;
    
11.  86 WDT->wdtim_mctrl = 0x70;
    
12.  87 /* Wait forever */
    
13.  88 while (1);
    
14.  89 }
15.