[PATCH AUTOSEL 4.20 149/304] watchdog: renesas_wdt: don't set divider while watchdog is running

[Sasha Levin]

From: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>

[ Upstream commit e990e12741877e9bfac402ca468f4007a75f6e2a ]

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@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: Fabrizio Castro <fabrizio.castro@xxxxxxxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Wim Van Sebroeck <wim@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/watchdog/renesas_wdt.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/watchdog/renesas_wdt.c b/drivers/watchdog/renesas_wdt.c
index 0d74c3e48979..55c9eb6c6e51 100644
--- 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();
-- 
2.19.1