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>

1 files changed, 25 insertions, 16 deletions

diff --git a/drivers/thermal/imx_thermal.c b/drivers/thermal/imx_thermal.c
index 0e35999ad8b2..5a1f1070b702 100644
--- a/drivers/thermal/imx_thermal.c
+++ b/drivers/thermal/imx_thermal.c
@@ -525,6 +525,30 @@ static int imx_thermal_probe(struct platform_device *pdev)
                 return ret;
         }
 
+        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 get thermal clk: %d\n", ret);
+                cpufreq_cooling_unregister(data->cdev);
+                return ret;
+        }
+
+        /*
+         * Thermal sensor needs clk on to get correct value, normally
+         * we should enable its clk before taking measurement and disable
+         * clk after measurement is done, but if alarm function is enabled,
+         * hardware will auto measure the temperature periodically, so we
+         * need to keep the clk always on for alarm function.
+         */
+        ret = clk_prepare_enable(data->thermal_clk);
+        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,
@@ -535,26 +559,11 @@ static int imx_thermal_probe(struct platform_device *pdev)
                 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;
         }
 
-        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
-                 * clk after measurement is done, but if alarm function is enabled,
-                 * hardware will auto measure the temperature periodically, so we
-                 * 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);
-        }
-
         /* Enable measurements at ~ 10 Hz */
         regmap_write(map, TEMPSENSE1 + REG_CLR, TEMPSENSE1_MEASURE_FREQ);
         measure_freq = DIV_ROUND_UP(32768, 10); /* 10 Hz */