[PATCH 5/5] watchdog: starfive-wdt: Drop runtime PM reference before registering watchdog

[Guenter Roeck <linux@roeck-us.net>]

In starfive_wdt_probe(), watchdog_register_device() is called before the
probe-time runtime PM reference is released via pm_runtime_put_sync(), and
any non-zero return value from pm_runtime_put_sync() is treated as a fatal
probe error.

If userspace (such as udev or a watchdog daemon) opens /dev/watchdog
immediately after watchdog_register_device() exposes the character device,
starfive_wdt_pm_start() increments the runtime PM usage count. The
subsequent pm_runtime_put_sync() in probe then decrements the usage count
to 1 and returns -EAGAIN (it may also return 1, -EBUSY, or -EPERM in
non-error idle conditions), causing starfive_wdt_probe() to unregister the
working watchdog device and fail probe.

When early_enable is not set, no hardware registers are accessed after
starfive_wdt_stop(). Release the probe-time runtime PM reference right
after starfive_wdt_stop() and before watchdog_register_device(), without
treating pm_runtime_put_sync() idle return codes as probe errors.

Fixes: 8bc22a2f1bf0 ("watchdog: starfive: Check pm_runtime_enabled() before decrementing usage counter")
Cc: Xingyu Wu <xingyu.wu@starfivetech.com>
Cc: Ziv Xu <ziv.xu@starfivetech.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/watchdog/starfive-wdt.c | 23 ++++++++++-------------
 1 file changed, 10 insertions(+), 13 deletions(-)

diff --git a/drivers/watchdog/starfive-wdt.c b/drivers/watchdog/starfive-wdt.c
index 817f84cc2807..d3eb29c45e6a 100644
--- a/drivers/watchdog/starfive-wdt.c
+++ b/drivers/watchdog/starfive-wdt.c
@@ -499,28 +499,25 @@ static int starfive_wdt_probe(struct platform_device *pdev)
 		set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
 	} else {
 		starfive_wdt_stop(wdt);
+		if (pm_runtime_enabled(&pdev->dev))
+			pm_runtime_put_sync(&pdev->dev);
 	}
 
 	ret = watchdog_register_device(&wdt->wdd);
-	if (ret)
-		goto err_exit;
-
-	if (!early_enable) {
-		if (pm_runtime_enabled(&pdev->dev)) {
-			ret = pm_runtime_put_sync(&pdev->dev);
-			if (ret)
-				goto err_unregister_wdt;
+	if (ret) {
+		if (watchdog_hw_running(&wdt->wdd)) {
+			starfive_wdt_stop(wdt);
+			if (pm_runtime_enabled(&pdev->dev))
+				pm_runtime_put_sync(&pdev->dev);
 		}
+		if (!pm_runtime_enabled(&pdev->dev))
+			starfive_wdt_disable_clock(wdt);
+		goto err_disable_pm;
 	}
 
 	return 0;
 
-err_unregister_wdt:
-	watchdog_unregister_device(&wdt->wdd);
-	goto err_disable_pm;
 err_exit:
-	if (watchdog_hw_running(&wdt->wdd))
-		starfive_wdt_stop(wdt);
 	if (pm_runtime_enabled(&pdev->dev))
 		pm_runtime_put_sync(&pdev->dev);
 	else
-- 
2.45.2