watchdog: imx2_wdt: restore previous timeout after suspend+resume

Web:        https://git.kernel.org/torvalds/c/0be267255cef64e1c58475baa7b25568355a3816
Commit:     0be267255cef64e1c58475baa7b25568355a3816
Parent:     38a1222ae4f364d5bd5221fe305dbb0889f45d15
Refname:    refs/heads/master
Author:     Martin Kaiser <[email protected]>
AuthorDate: Mon Jan 1 18:26:47 2018 +0100
Committer:  Wim Van Sebroeck <[email protected]>
CommitDate: Sun Jan 21 12:44:58 2018 +0100

    watchdog: imx2_wdt: restore previous timeout after suspend+resume
    
    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.
    
    Signed-off-by: Martin Kaiser <[email protected]>
    Cc: [email protected]
    Reviewed-by: Guenter Roeck <[email protected]>
    Signed-off-by: Guenter Roeck <[email protected]>
    Signed-off-by: Wim Van Sebroeck <[email protected]>
---
 drivers/watchdog/imx2_wdt.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/watchdog/imx2_wdt.c b/drivers/watchdog/imx2_wdt.c
index 4874b0f18650..518dfa1047cb 100644
--- a/drivers/watchdog/imx2_wdt.c
+++ b/drivers/watchdog/imx2_wdt.c
@@ -169,15 +169,21 @@ static int imx2_wdt_ping(struct watchdog_device *wdog)
 	return 0;
 }
 
-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;
 }
 
@@ -371,7 +377,11 @@ static int imx2_wdt_suspend(struct device *dev)
 
 	/* 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);
 	}
 
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