Re: [PATCH] watchdog: imx2_wdt: restore previous timeout after suspend+resume

From: Guenter Roeck
Date: Fri Dec 29 2017 - 11:10:28 EST

On 12/29/2017 05:59 AM, Martin Kaiser wrote:
When the watchdog device is suspended, its timeout is set to the maximum
value. During resume, the previously set timeout should be restored.
This does not work at the moment.

The suspend function calls

imx2_wdt_set_timeout(wdog, IMX2_WDT_MAX_TIME);

and resume reverts this by calling

imx2_wdt_set_timeout(wdog, wdog->timeout);

However, imx2_wdt_set_timeout() updates wdog->timeout. Therefore,
wdog->timeout is set to IMX2_WDT_MAX_TIME when we enter the resume

Fix this by setting wdog->timeout to the previous value at the end of
the suspend function. This manual update makes wdog->timeout different
from the actual setting in the hardware. This should be ok in our case
as kernel code is not running while we're suspended.

Signed-off-by: Martin Kaiser <martin@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx

That works, though it is a bit hackish. Better would be to have a function
such as _imx2_wdt_set_timeout() which doesn't actually update wdt->timeout
and could be called from all the other places doing the same.
Separate patch, maybe.

Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>

drivers/watchdog/imx2_wdt.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
index 4874b0f..66efcc0 100644
--- a/drivers/watchdog/imx2_wdt.c
+++ b/drivers/watchdog/imx2_wdt.c
@@ -368,6 +368,7 @@ static int imx2_wdt_suspend(struct device *dev)
struct watchdog_device *wdog = dev_get_drvdata(dev);
struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);
+ unsigned int resume_timeout = wdog->timeout;
/* The watchdog IP block is running */
if (imx2_wdt_is_running(wdev)) {
@@ -377,6 +378,7 @@ static int imx2_wdt_suspend(struct device *dev)
+ wdog->timeout = resume_timeout;
return 0;