serial: 8250_dw: Use devm_clk_get_optional() to get the input clock

Simplify the code which fetches the input clock by using
devm_clk_get_optional(). This comes with a small functional change: previously
all errors were ignored except deferred probe. Now all errors are
treated as errors. If no input clock is present devm_clk_get_optional() will
return NULL instead of an error which matches the behavior of the old code.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20190925162617.30368-1-andriy.shevchenko@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250_dw.c

@@ -280,9 +280,6 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
 	long rate;
 	int ret;
 
-	if (IS_ERR(d->clk))
-		goto out;
-
 	clk_disable_unprepare(d->clk);
 	rate = clk_round_rate(d->clk, baud * 16);
 	if (rate < 0)
@@ -293,7 +290,9 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
 		ret = clk_set_rate(d->clk, rate);
 	clk_prepare_enable(d->clk);
 
-	if (!ret)
+	if (ret)
+		goto out;
+
 	p->uartclk = rate;
 
 out:
@@ -472,19 +471,18 @@ static int dw8250_probe(struct platform_device *pdev)
 	device_property_read_u32(dev, "clock-frequency", &p->uartclk);
 
 	/* If there is separate baudclk, get the rate from it. */
-	data->clk = devm_clk_get(dev, "baudclk");
-	if (IS_ERR(data->clk) && PTR_ERR(data->clk) != -EPROBE_DEFER)
-		data->clk = devm_clk_get(dev, NULL);
-	if (IS_ERR(data->clk) && PTR_ERR(data->clk) == -EPROBE_DEFER)
-		return -EPROBE_DEFER;
-	if (!IS_ERR_OR_NULL(data->clk)) {
+	data->clk = devm_clk_get_optional(dev, "baudclk");
+	if (data->clk == NULL)
+		data->clk = devm_clk_get_optional(dev, NULL);
+	if (IS_ERR(data->clk))
+		return PTR_ERR(data->clk);
+
 	err = clk_prepare_enable(data->clk);
 	if (err)
-			dev_warn(dev, "could not enable optional baudclk: %d\n",
-				 err);
-		else
+		dev_warn(dev, "could not enable optional baudclk: %d\n", err);
+
+	if (data->clk)
 		p->uartclk = clk_get_rate(data->clk);
-	}
 
 	/* If no clock rate is defined, fail. */
 	if (!p->uartclk) {
@@ -493,18 +491,17 @@ static int dw8250_probe(struct platform_device *pdev)
 		goto err_clk;
 	}
 
-	data->pclk = devm_clk_get(dev, "apb_pclk");
-	if (IS_ERR(data->pclk) && PTR_ERR(data->pclk) == -EPROBE_DEFER) {
-		err = -EPROBE_DEFER;
+	data->pclk = devm_clk_get_optional(dev, "apb_pclk");
+	if (IS_ERR(data->pclk)) {
+		err = PTR_ERR(data->pclk);
 		goto err_clk;
 	}
-	if (!IS_ERR(data->pclk)) {
+
 	err = clk_prepare_enable(data->pclk);
 	if (err) {
 		dev_err(dev, "could not enable apb_pclk\n");
 		goto err_clk;
 	}
-	}
 
 	data->rst = devm_reset_control_get_optional_exclusive(dev, NULL);
 	if (IS_ERR(data->rst)) {
@@ -546,11 +543,9 @@ static int dw8250_probe(struct platform_device *pdev)
 	reset_control_assert(data->rst);
 
 err_pclk:
-	if (!IS_ERR(data->pclk))
 	clk_disable_unprepare(data->pclk);
 
 err_clk:
-	if (!IS_ERR(data->clk))
 	clk_disable_unprepare(data->clk);
 
 	return err;
@@ -567,10 +562,8 @@ static int dw8250_remove(struct platform_device *pdev)
 
 	reset_control_assert(data->rst);
 
-	if (!IS_ERR(data->pclk))
 	clk_disable_unprepare(data->pclk);
 
-	if (!IS_ERR(data->clk))
 	clk_disable_unprepare(data->clk);
 
 	pm_runtime_disable(dev);
@@ -604,10 +597,8 @@ static int dw8250_runtime_suspend(struct device *dev)
 {
 	struct dw8250_data *data = dev_get_drvdata(dev);
 
-	if (!IS_ERR(data->clk))
 	clk_disable_unprepare(data->clk);
 
-	if (!IS_ERR(data->pclk))
 	clk_disable_unprepare(data->pclk);
 
 	return 0;
@@ -617,10 +608,8 @@ static int dw8250_runtime_resume(struct device *dev)
 {
 	struct dw8250_data *data = dev_get_drvdata(dev);
 
-	if (!IS_ERR(data->pclk))
 	clk_prepare_enable(data->pclk);
 
-	if (!IS_ERR(data->clk))
 	clk_prepare_enable(data->clk);
 
 	return 0;