watchdog: renesas_wdt: don't set divider while watchdog is running

The datasheet says we must stop the timer before changing the clock
divider. This can happen when the restart handler is called while the
watchdog is running.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

diff --git a/drivers/watchdog/renesas_wdt.c b/drivers/watchdog/renesas_wdt.c
index b570962e84f32f3fad6a80d0aebd4c0e242b2fcb..c450e23e24a898529fe4710bf88af95b23c7b1a8 100644 (file)
--- a/drivers/watchdog/renesas_wdt.c
+++ b/drivers/watchdog/renesas_wdt.c
@@ -74,12 +74,17 @@ static int rwdt_init_timeout(struct watchdog_device *wdev)
 static int rwdt_start(struct watchdog_device *wdev)
 {
        struct rwdt_priv *priv = watchdog_get_drvdata(wdev);
+       u8 val;
 
        pm_runtime_get_sync(wdev->parent);
 
-       rwdt_write(priv, 0, RWTCSRB);
-       rwdt_write(priv, priv->cks, RWTCSRA);
+       /* Stop the timer before we modify any register */
+       val = readb_relaxed(priv->base + RWTCSRA) & ~RWTCSRA_TME;
+       rwdt_write(priv, val, RWTCSRA);
+
        rwdt_init_timeout(wdev);
+       rwdt_write(priv, priv->cks, RWTCSRA);
+       rwdt_write(priv, 0, RWTCSRB);
 
        while (readb_relaxed(priv->base + RWTCSRA) & RWTCSRA_WRFLG)
                cpu_relax();