This is a note to let you know that I've just added the patch titled
watchdog: ath79_wdt: avoid spurious restarts on AR934x
to the 3.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
watchdog-ath79_wdt-avoid-spurious-restarts-on-ar934x.patch
and it can be found in the queue-3.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 23afeb613ec0e10aecfae7838a14d485db62ac52 Mon Sep 17 00:00:00 2001
From: Gabor Juhos <juhosg@xxxxxxxxxxx>
Date: Wed, 16 Apr 2014 11:34:41 +0200
Subject: watchdog: ath79_wdt: avoid spurious restarts on AR934x
From: Gabor Juhos <juhosg@xxxxxxxxxxx>
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@xxxxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Wim Van Sebroeck <wim@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/watchdog/ath79_wdt.c | 10 ++++++++++
1 file changed, 10 insertions(+)
--- 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/io.h>
@@ -90,6 +91,15 @@ static inline void ath79_wdt_keepalive(v
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);
Patches currently in stable-queue which might be from juhosg@xxxxxxxxxxx are
queue-3.15/watchdog-ath79_wdt-avoid-spurious-restarts-on-ar934x.patch
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