Commit 23afeb61 authored Apr 16, 2014 by Gabor Juhos Committed by Wim Van Sebroeck Jun 10, 2014

watchdog: ath79_wdt: avoid spurious restarts on AR934x



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>
Cc: <stable@vger.kernel.org>

parent ff4e0ae5

drivers/watchdog/ath79_wdt.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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(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);

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