watchdog: tangox_wdt: test clock rate to avoid division by 0

The clk API may return 0 on clk_get_rate, so we should check the result before
using it as a divisor. For this, refactor the code to use a central
error path.
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/tangox_wdt.c

@@ -139,6 +139,10 @@ static int tangox_wdt_probe(struct platform_device *pdev)
 		return err;
 
 	dev->clk_rate = clk_get_rate(dev->clk);
+	if (!dev->clk_rate) {
+		err = -EINVAL;
+		goto err;
+	}
 
 	dev->wdt.parent = &pdev->dev;
 	dev->wdt.info = &tangox_wdt_info;
@@ -171,10 +175,8 @@ static int tangox_wdt_probe(struct platform_device *pdev)
 	}
 
 	err = watchdog_register_device(&dev->wdt);
-	if (err) {
-		clk_disable_unprepare(dev->clk);
-		return err;
-	}
+	if (err)
+		goto err;
 
 	platform_set_drvdata(pdev, dev);
 
@@ -187,6 +189,10 @@ static int tangox_wdt_probe(struct platform_device *pdev)
 	dev_info(&pdev->dev, "SMP86xx/SMP87xx watchdog registered\n");
 
 	return 0;
+
+ err:
+	clk_disable_unprepare(dev->clk);
+	return err;
 }
 
 static int tangox_wdt_remove(struct platform_device *pdev)