watchdog: meson_gxbb_wdt: Convert to use device managed functions and other improvements

Use device managed functions to simplify error handling, reduce
source code size, improve readability, and reduce the likelyhood of bugs.
Other improvements as listed below.

The conversion was done automatically with coccinelle using the
following semantic patches. The semantic patches and the scripts
used to generate this commit log are available at
https://github.com/groeck/coccinelle-patches

- Drop assignments to otherwise unused variables
- Drop unnecessary braces around conditional return statements
- Drop empty remove function
- Use devm_add_action_or_reset() for calls to clk_disable_unprepare
- Introduce local variable 'struct device *dev' and use it instead of
  dereferencing it repeatedly
- Use devm_watchdog_register_driver() to register watchdog device
- Replace shutdown function with call to watchdog_stop_on_reboot()

Cc: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>

drivers/watchdog/meson_gxbb_wdt.c

@@ -136,12 +136,18 @@ static const struct of_device_id meson_gxbb_wdt_dt_ids[] = {
 };
 MODULE_DEVICE_TABLE(of, meson_gxbb_wdt_dt_ids);
 
+static void meson_clk_disable_unprepare(void *data)
+{
+	clk_disable_unprepare(data);
+}
+
 static int meson_gxbb_wdt_probe(struct platform_device *pdev)
 {
+	struct device *dev = &pdev->dev;
 	struct meson_gxbb_wdt *data;
 	int ret;
 
-	data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
 	if (!data)
 		return -ENOMEM;
 
@@ -149,17 +155,21 @@ static int meson_gxbb_wdt_probe(struct platform_device *pdev)
 	if (IS_ERR(data->reg_base))
 		return PTR_ERR(data->reg_base);
 
-	data->clk = devm_clk_get(&pdev->dev, NULL);
+	data->clk = devm_clk_get(dev, NULL);
 	if (IS_ERR(data->clk))
 		return PTR_ERR(data->clk);
 
 	ret = clk_prepare_enable(data->clk);
 	if (ret)
 		return ret;
+	ret = devm_add_action_or_reset(dev, meson_clk_disable_unprepare,
+				       data->clk);
+	if (ret)
+		return ret;
 
 	platform_set_drvdata(pdev, data);
 
-	data->wdt_dev.parent = &pdev->dev;
+	data->wdt_dev.parent = dev;
 	data->wdt_dev.info = &meson_gxbb_wdt_info;
 	data->wdt_dev.ops = &meson_gxbb_wdt_ops;
 	data->wdt_dev.max_hw_heartbeat_ms = GXBB_WDT_TCNT_SETUP_MASK;
@@ -176,37 +186,12 @@ static int meson_gxbb_wdt_probe(struct platform_device *pdev)
 
 	meson_gxbb_wdt_set_timeout(&data->wdt_dev, data->wdt_dev.timeout);
 
-	ret = watchdog_register_device(&data->wdt_dev);
-	if (ret) {
-		clk_disable_unprepare(data->clk);
-		return ret;
-	}
-
-	return 0;
-}
-
-static int meson_gxbb_wdt_remove(struct platform_device *pdev)
-{
-	struct meson_gxbb_wdt *data = platform_get_drvdata(pdev);
-
-	watchdog_unregister_device(&data->wdt_dev);
-
-	clk_disable_unprepare(data->clk);
-
-	return 0;
-}
-
-static void meson_gxbb_wdt_shutdown(struct platform_device *pdev)
-{
-	struct meson_gxbb_wdt *data = platform_get_drvdata(pdev);
-
-	meson_gxbb_wdt_stop(&data->wdt_dev);
+	watchdog_stop_on_reboot(&data->wdt_dev);
+	return devm_watchdog_register_device(dev, &data->wdt_dev);
 }
 
 static struct platform_driver meson_gxbb_wdt_driver = {
 	.probe	= meson_gxbb_wdt_probe,
-	.remove	= meson_gxbb_wdt_remove,
-	.shutdown = meson_gxbb_wdt_shutdown,
 	.driver = {
 		.name = "meson-gxbb-wdt",
 		.pm = &meson_gxbb_wdt_pm_ops,