Patch "watchdog: imx2_wdt: restore previous timeout after suspend+resume" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

watchdog: imx2_wdt: restore previous timeout after suspend+resume

to the 4.4-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-imx2_wdt-restore-previous-timeout-after-suspend-resume.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Martin Kaiser <[email protected]>
Date: Mon, 1 Jan 2018 18:26:47 +0100
Subject: watchdog: imx2_wdt: restore previous timeout after suspend+resume

From: Martin Kaiser <[email protected]>

commit 0be267255cef64e1c58475baa7b25568355a3816 upstream.

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 function.

Fix this by adding a new function __imx2_wdt_set_timeout() which only updates the hardware settings. imx2_wdt_set_timeout() now calls __imx2_wdt_set_timeout() and then saves the new timeout to wdog->timeout.

During suspend, we call __imx2_wdt_set_timeout() directly so that wdog->timeout won't be updated and we can restore the previous value during resume. This approach makes wdog->timeout different from the actual setting in the hardware which is usually not a good thing. However, the two differ only while we're suspended and no kernel code is running, so it should be ok in this case.

---
 drivers/watchdog/imx2_wdt.c |   20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

@@ -161,15 +161,21 @@ static void imx2_wdt_timer_ping(unsigned
 	mod_timer(&wdev->timer, jiffies + wdog->timeout * HZ / 2);
 }
 
-static int imx2_wdt_set_timeout(struct watchdog_device *wdog,
-				unsigned int new_timeout)
+static void __imx2_wdt_set_timeout(struct watchdog_device *wdog,
+				   unsigned int new_timeout)
 {
 	struct imx2_wdt_device *wdev = watchdog_get_drvdata(wdog);
 
-	wdog->timeout = new_timeout;
-
 	regmap_update_bits(wdev->regmap, IMX2_WDT_WCR, IMX2_WDT_WCR_WT,
 			   WDOG_SEC_TO_COUNT(new_timeout));
+}
+
+static int imx2_wdt_set_timeout(struct watchdog_device *wdog,
+				unsigned int new_timeout)
+{
+	__imx2_wdt_set_timeout(wdog, new_timeout);
+
+	wdog->timeout = new_timeout;
 	return 0;
 }
 

@@ -353,7 +359,11 @@ static int imx2_wdt_suspend(struct devic
 
 	/* The watchdog IP block is running */
 	if (imx2_wdt_is_running(wdev)) {
-		imx2_wdt_set_timeout(wdog, IMX2_WDT_MAX_TIME);
+		/*
+		 * Don't update wdog->timeout, we'll restore the current value
+		 * during resume.
+		 */
+		__imx2_wdt_set_timeout(wdog, IMX2_WDT_MAX_TIME);
 		imx2_wdt_ping(wdog);
 
 		/* The watchdog is not active */

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/watchdog-imx2_wdt-restore-previous-timeout-after-suspend-resume.patch