thermal/drivers/broadcom: Fix race between removal and clock disable

During the probe, driver enables clocks necessary to access registers
(in get_temp()) and then registers thermal zone with managed-resources
(devm) interface.  Removal of device is not done in reversed order,
because:
1. Clock will be disabled in driver remove() callback - thermal zone is
   still registered and accessible to users,
2. devm interface will unregister thermal zone.

This leaves short window between (1) and (2) for accessing the
get_temp() callback with disabled clock.

Fix this by enabling clock also via devm-interface, so entire cleanup
path will be in proper, reversed order.

Fixes: 8454c8c ("thermal/drivers/bcm2835: Remove buggy call to thermal_of_zone_unregister")
Cc: [email protected]
Signed-off-by: Krzysztof Kozlowski <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Daniel Lezcano <[email protected]>

Author: krzk

drivers/thermal/broadcom/bcm2835_thermal.c

@@ -185,18 +185,14 @@ static int bcm2835_thermal_probe(struct platform_device *pdev)
 		return err;
 	}
 
-	data->clk = devm_clk_get(&pdev->dev, NULL);
+	data->clk = devm_clk_get_enabled(&pdev->dev, NULL);
 	if (IS_ERR(data->clk)) {
 		err = PTR_ERR(data->clk);
 		if (err != -EPROBE_DEFER)
 			dev_err(&pdev->dev, "Could not get clk: %d\n", err);
 		return err;
 	}
 
-	err = clk_prepare_enable(data->clk);
-	if (err)
-		return err;
-
 	rate = clk_get_rate(data->clk);
 	if ((rate < 1920000) || (rate > 5000000))
 		dev_warn(&pdev->dev,
@@ -211,7 +207,7 @@ static int bcm2835_thermal_probe(struct platform_device *pdev)
 		dev_err(&pdev->dev,
 			"Failed to register the thermal device: %d\n",
 			err);
-		goto err_clk;
+		return err;
 	}
 
 	/*
@@ -236,7 +232,7 @@ static int bcm2835_thermal_probe(struct platform_device *pdev)
 			dev_err(&pdev->dev,
 				"Not able to read trip_temp: %d\n",
 				err);
-			goto err_tz;
+			return err;
 		}
 
 		/* set bandgap reference voltage and enable voltage regulator */
@@ -269,25 +265,18 @@ static int bcm2835_thermal_probe(struct platform_device *pdev)
 	 */
 	err = thermal_add_hwmon_sysfs(tz);
 	if (err)
-		goto err_tz;
+		return err;
 
 	bcm2835_thermal_debugfs(pdev);
 
 	return 0;
-err_tz:
-	devm_thermal_of_zone_unregister(&pdev->dev, tz);
-err_clk:
-	clk_disable_unprepare(data->clk);
-
-	return err;
 }
 
 static void bcm2835_thermal_remove(struct platform_device *pdev)
 {
 	struct bcm2835_thermal_data *data = platform_get_drvdata(pdev);
 
 	debugfs_remove_recursive(data->debugfsdir);
-	clk_disable_unprepare(data->clk);
 }
 
 static struct platform_driver bcm2835_thermal_driver = {