usb: misc: usb3503: get optional clock by devm_clk_get_optional()

When the driver tries to get optional clock, it ignores all errors except
-EPROBE_DEFER, but if only ignores -ENOENT, it will cover some real errors,
such as -ENOMEM, so use devm_clk_get_optional() to get optional clock.
And remove unnecessary stack variable clk.

Cc: Dongjin Kim <tobetter@gmail.com>
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/misc/usb3503.c

@@ -172,7 +172,6 @@ static int usb3503_probe(struct usb3503 *hub)
 		hub->gpio_reset		= pdata->gpio_reset;
 		hub->mode		= pdata->initial_mode;
 	} else if (np) {
-		struct clk *clk;
 		u32 rate = 0;
 		hub->port_off_mask = 0;
 
@@ -198,34 +197,29 @@ static int usb3503_probe(struct usb3503 *hub)
 			}
 		}
 
-		clk = devm_clk_get(dev, "refclk");
-		if (IS_ERR(clk) && PTR_ERR(clk) != -ENOENT) {
+		hub->clk = devm_clk_get_optional(dev, "refclk");
+		if (IS_ERR(hub->clk)) {
 			dev_err(dev, "unable to request refclk (%ld)\n",
-					PTR_ERR(clk));
-			return PTR_ERR(clk);
+					PTR_ERR(hub->clk));
+			return PTR_ERR(hub->clk);
 		}
 
-		if (!IS_ERR(clk)) {
-			hub->clk = clk;
-
-			if (rate != 0) {
-				err = clk_set_rate(hub->clk, rate);
-				if (err) {
-					dev_err(dev,
-						"unable to set reference clock rate to %d\n",
-						(int) rate);
-					return err;
-				}
-			}
-
-			err = clk_prepare_enable(hub->clk);
+		if (rate != 0) {
+			err = clk_set_rate(hub->clk, rate);
 			if (err) {
 				dev_err(dev,
-					"unable to enable reference clock\n");
+					"unable to set reference clock rate to %d\n",
+					(int)rate);
 				return err;
 			}
 		}
 
+		err = clk_prepare_enable(hub->clk);
+		if (err) {
+			dev_err(dev, "unable to enable reference clock\n");
+			return err;
+		}
+
 		property = of_get_property(np, "disabled-ports", &len);
 		if (property && (len / sizeof(u32)) > 0) {
 			int i;
@@ -324,8 +318,7 @@ static int usb3503_i2c_remove(struct i2c_client *i2c)
 	struct usb3503 *hub;
 
 	hub = i2c_get_clientdata(i2c);
-	if (hub->clk)
-		clk_disable_unprepare(hub->clk);
+	clk_disable_unprepare(hub->clk);
 
 	return 0;
 }
@@ -348,8 +341,7 @@ static int usb3503_platform_remove(struct platform_device *pdev)
 	struct usb3503 *hub;
 
 	hub = platform_get_drvdata(pdev);
-	if (hub->clk)
-		clk_disable_unprepare(hub->clk);
+	clk_disable_unprepare(hub->clk);
 
 	return 0;
 }
@@ -358,18 +350,14 @@ static int usb3503_platform_remove(struct platform_device *pdev)
 static int usb3503_suspend(struct usb3503 *hub)
 {
 	usb3503_switch_mode(hub, USB3503_MODE_STANDBY);
-
-	if (hub->clk)
-		clk_disable_unprepare(hub->clk);
+	clk_disable_unprepare(hub->clk);
 
 	return 0;
 }
 
 static int usb3503_resume(struct usb3503 *hub)
 {
-	if (hub->clk)
-		clk_prepare_enable(hub->clk);
-
+	clk_prepare_enable(hub->clk);
 	usb3503_switch_mode(hub, hub->mode);
 
 	return 0;