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authorGabor Juhos <juhosg@openwrt.org>2014-04-16 11:34:41 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-07-06 18:57:27 -0700
commit1814990c7c2a6582b6387d20a09b1396ce6e4bfe (patch)
treeebe4c2da157d8d874aac8fa3c341c5987f937a60 /drivers
parent6439c083d416ea6c038081efd2906a059eee0ae8 (diff)
watchdog: ath79_wdt: avoid spurious restarts on AR934x
commit 23afeb613ec0e10aecfae7838a14d485db62ac52 upstream. On some AR934x based systems, where the frequency of the AHB bus is relatively high, the built-in watchdog causes a spurious restart when it gets enabled. The possible cause of these restarts is that the timeout value written into the TIMER register does not reaches the hardware in time. Add an explicit delay into the ath79_wdt_enable function to avoid the spurious restarts. Signed-off-by: Gabor Juhos <juhosg@openwrt.org> Reviewed-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Wim Van Sebroeck <wim@iguana.be> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/watchdog/ath79_wdt.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/watchdog/ath79_wdt.c b/drivers/watchdog/ath79_wdt.c
index 9fa1f69dac1..61098cd5439 100644
--- a/drivers/watchdog/ath79_wdt.c
+++ b/drivers/watchdog/ath79_wdt.c
@@ -20,6 +20,7 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/bitops.h>
+#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/init.h>
@@ -91,6 +92,15 @@ static inline void ath79_wdt_keepalive(void)
static inline void ath79_wdt_enable(void)
{
ath79_wdt_keepalive();
+
+ /*
+ * Updating the TIMER register requires a few microseconds
+ * on the AR934x SoCs at least. Use a small delay to ensure
+ * that the TIMER register is updated within the hardware
+ * before enabling the watchdog.
+ */
+ udelay(2);
+
ath79_wdt_wr(WDOG_REG_CTRL, WDOG_CTRL_ACTION_FCR);
/* flush write */
ath79_wdt_rr(WDOG_REG_CTRL);