ti: wdt: omap: Disable watchdog timer before performing initialization

The OMAP WDT IP block requires to be stopped before any write to its
registers is performed.

This problem has been thoroughly described in Linux kernel:

"watchdog: omap: assert the counter being stopped before reprogramming:
SHA1: 530c11d432727c697629ad5f9d00ee8e2864d453

Signed-off-by: Lukasz Majewski <lukma@denx.de>
Reviewed-by: Tom Rini <trini@konsulko.com>

diff --git a/drivers/watchdog/omap_wdt.c b/drivers/watchdog/omap_wdt.c
index 7ea4b604cd6376d500944bd3ba81937df2a91cc1..7b1f42943293e7e5015b6e1450d820bb1c4bb427 100644 (file)
--- a/drivers/watchdog/omap_wdt.c
+++ b/drivers/watchdog/omap_wdt.c
@@ -81,10 +81,32 @@ static int omap_wdt_set_timeout(unsigned int timeout)
        return 0;
 }
 
+void hw_watchdog_disable(void)
+{
+       struct wd_timer *wdt = (struct wd_timer *)WDT_BASE;
+
+       /*
+        * Disable watchdog
+        */
+       writel(0xAAAA, &wdt->wdtwspr);
+       while (readl(&wdt->wdtwwps) != 0x0)
+               ;
+       writel(0x5555, &wdt->wdtwspr);
+       while (readl(&wdt->wdtwwps) != 0x0)
+               ;
+}
+
 void hw_watchdog_init(void)
 {
        struct wd_timer *wdt = (struct wd_timer *)WDT_BASE;
 
+       /*
+        * Make sure the watchdog is disabled. This is unfortunately required
+        * because writing to various registers with the watchdog running has no
+        * effect.
+        */
+       hw_watchdog_disable();
+
        /* initialize prescaler */
        while (readl(&wdt->wdtwwps) & WDT_WWPS_PEND_WCLR)
                ;
@@ -104,18 +126,3 @@ void hw_watchdog_init(void)
        while ((readl(&wdt->wdtwwps)) & WDT_WWPS_PEND_WSPR)
                ;
 }
-
-void hw_watchdog_disable(void)
-{
-       struct wd_timer *wdt = (struct wd_timer *)WDT_BASE;
-
-       /*
-        * Disable watchdog
-        */
-       writel(0xAAAA, &wdt->wdtwspr);
-       while (readl(&wdt->wdtwwps) != 0x0)
-               ;
-       writel(0x5555, &wdt->wdtwspr);
-       while (readl(&wdt->wdtwwps) != 0x0)
-               ;
-}