imx: thermal: imx_get_temp might be called before sensor clock is prepared

imx_get_temp might be called before the sensor clock is prepared
thus resulting in a timeout of the first attempt to read temp:
thermal thermal_zone0: failed to read out thermal zone 0
Happened to me on a Utilite Standard with IMX6 Dual SoC.

Reason is that in imx_thermal_probe thermal_zone_device_register
is called before the sensor clock is prepared.
thermal_zone_device_register however calls
thermal_zone_device_update which eventually calls imx_get_temp.

Fix this by preparing the clock before calling
thermal_zone_device_register.
Signed-off-by: Heiner Kallweit <heiner.kallweit@web.de>
Signed-off-by: Eduardo Valentin <edubezval@gmail.com>

drivers/thermal/imx_thermal.c

@@ -525,24 +525,16 @@ static int imx_thermal_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	data->tz = thermal_zone_device_register("imx_thermal_zone",
-						IMX_TRIP_NUM,
-						BIT(IMX_TRIP_PASSIVE), data,
-						&imx_tz_ops, NULL,
-						IMX_PASSIVE_DELAY,
-						IMX_POLLING_DELAY);
-	if (IS_ERR(data->tz)) {
-		ret = PTR_ERR(data->tz);
+	data->thermal_clk = devm_clk_get(&pdev->dev, NULL);
+	if (IS_ERR(data->thermal_clk)) {
+		ret = PTR_ERR(data->thermal_clk);
+		if (ret != -EPROBE_DEFER)
 			dev_err(&pdev->dev,
-			"failed to register thermal zone device %d\n", ret);
+				"failed to get thermal clk: %d\n", ret);
 		cpufreq_cooling_unregister(data->cdev);
 		return ret;
 	}
 
-	data->thermal_clk = devm_clk_get(&pdev->dev, NULL);
-	if (IS_ERR(data->thermal_clk)) {
-		dev_warn(&pdev->dev, "failed to get thermal clk!\n");
-	} else {
 	/*
 	 * Thermal sensor needs clk on to get correct value, normally
 	 * we should enable its clk before taking measurement and disable
@@ -551,8 +543,25 @@ static int imx_thermal_probe(struct platform_device *pdev)
 	 * need to keep the clk always on for alarm function.
 	 */
 	ret = clk_prepare_enable(data->thermal_clk);
-		if (ret)
-			dev_warn(&pdev->dev, "failed to enable thermal clk: %d\n", ret);
+	if (ret) {
+		dev_err(&pdev->dev, "failed to enable thermal clk: %d\n", ret);
+		cpufreq_cooling_unregister(data->cdev);
+		return ret;
+	}
+
+	data->tz = thermal_zone_device_register("imx_thermal_zone",
+						IMX_TRIP_NUM,
+						BIT(IMX_TRIP_PASSIVE), data,
+						&imx_tz_ops, NULL,
+						IMX_PASSIVE_DELAY,
+						IMX_POLLING_DELAY);
+	if (IS_ERR(data->tz)) {
+		ret = PTR_ERR(data->tz);
+		dev_err(&pdev->dev,
+			"failed to register thermal zone device %d\n", ret);
+		clk_disable_unprepare(data->thermal_clk);
+		cpufreq_cooling_unregister(data->cdev);
+		return ret;
 	}
 
 	/* Enable measurements at ~ 10 Hz */