[PATCH v2 6/6] watchdog: starfive: release early_enable PM refcount on remove

[William Theesfeld]

When early_enable starts the hardware at probe time, the runtime PM
reference taken by pm_runtime_resume_and_get() is intentionally kept
to hold the device runtime-resumed.  In the normal (userspace-opened)
case the watchdog framework unwinds that reference via pm_stop() on
close, and again via stop_on_unregister() during
watchdog_unregister_device().

But watchdog_unregister_device() only runs the stop path when
WDOG_ACTIVE is set (see drivers/watchdog/watchdog_dev.c).  If
early_enable started the hardware and userspace never opened it,
WDOG_HW_RUNNING is set without WDOG_ACTIVE: unregister returns
without touching pm_stop, and the probe-time PM reference is leaked.

Drop that reference in starfive_wdt_remove() before
pm_runtime_disable() runs, when WDOG_HW_RUNNING is still asserted.

Signed-off-by: William Theesfeld <william@xxxxxxxxxxxxx>
---
 drivers/watchdog/starfive-wdt.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/watchdog/starfive-wdt.c b/drivers/watchdog/starfive-wdt.c
index 848935dc6..d9175b045 100644
--- a/drivers/watchdog/starfive-wdt.c
+++ b/drivers/watchdog/starfive-wdt.c
@@ -538,6 +538,19 @@ static void starfive_wdt_remove(struct platform_device *pdev)
 	starfive_wdt_stop(wdt);
 	watchdog_unregister_device(&wdt->wdd);
 
+	/*
+	 * watchdog_unregister_device() only calls our pm_stop op when
+	 * WDOG_ACTIVE is set.  When early_enable started the hardware at
+	 * probe time and userspace never opened the watchdog, the framework
+	 * state is WDOG_HW_RUNNING without WDOG_ACTIVE: the unregister path
+	 * leaves the runtime PM reference taken at probe outstanding.  Drop
+	 * it here before disabling runtime PM so the usage counter does not
+	 * leak.
+	 */
+	if (test_bit(WDOG_HW_RUNNING, &wdt->wdd.status) &&
+	    pm_runtime_enabled(&pdev->dev))
+		pm_runtime_put_sync(&pdev->dev);
+
 	if (pm_runtime_enabled(&pdev->dev))
 		pm_runtime_disable(&pdev->dev);
 	else
-- 
2.54.0