UBOOT WDT驱动流程

#define ms_to_ticks(t)    (((t << 8) / 1000) - 1)
#define ticks_to_ms(t)    (((t + 1) * 1000) >> 8)

/* Hardware timeout in seconds */
#define WDT_HW_TIMEOUT 2

/*
 * Set the watchdog time interval in 1/256Hz (write-once)
 * Counter is 12 bit.
 */
static int wdt_settimeout(unsigned int timeout)
{
    unsigned int reg;
     wdt_t *wd     = (wdt_t *) WDT_BASE;

    /* Check if disabled */
    if (readl(&wd->mr) & WDT_MR_WDDIS) {
        printf("sorry, watchdog is disabled\n");
        return -1;
    }

    /*
     * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
     *
     * Since WDV is a 12-bit counter, the maximum period is
     * 4096 / 256 = 16 seconds.
     */

    reg = WDT_MR_WDRSTEN        /* causes watchdog reset */
        | WDT_MR_WDDBGHLT        /* disabled in debug mode */
        | WDT_MR_WDD(0xfff)    /* restart at any time */
        | WDT_MR_WDV(timeout);    /* timer value */

    writel(reg, &wd->mr);

    return 0;
}

void hw_watchdog_reset(void)
{
    wdt_t *wd     = (wdt_t *) WDT_BASE;
    writel(WDT_CR_WDRSTT | WDT_CR_KEY, &wd->cr);
}

void hw_watchdog_init(void)
{
    /* 16 seconds timer, resets enabled */
    at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
}