linux-kernel - [PATCH 01/12] thermal/drivers/broadcom: fix race between removal and clock disable

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Message-Id: <20240709-thermal-probe-v1-1-241644e2b6e0@linaro.org>
Date: Tue, 09 Jul 2024 14:59:31 +0200
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>, 
 Daniel Lezcano <daniel.lezcano@...aro.org>, Zhang Rui <rui.zhang@...el.com>, 
 Lukasz Luba <lukasz.luba@....com>, 
 Florian Fainelli <florian.fainelli@...adcom.com>, 
 Ray Jui <rjui@...adcom.com>, Scott Branden <sbranden@...adcom.com>, 
 Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>, 
 Bartlomiej Zolnierkiewicz <bzolnier@...il.com>, 
 Krzysztof Kozlowski <krzk@...nel.org>, 
 Alim Akhtar <alim.akhtar@...sung.com>, Shawn Guo <shawnguo@...nel.org>, 
 Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>, Amit Kucheria <amitk@...nel.org>, 
 Thara Gopinath <thara.gopinath@...il.com>
Cc: linux-pm@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org, 
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 linux-samsung-soc@...r.kernel.org, imx@...ts.linux.dev, 
 linux-arm-msm@...r.kernel.org, stable@...r.kernel.org, 
 Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Subject: [PATCH 01/12] 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: 8454c8c09c77 ("thermal/drivers/bcm2835: Remove buggy call to thermal_of_zone_unregister")
Cc: <stable@...r.kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
---
 drivers/thermal/broadcom/bcm2835_thermal.c | 19 ++++---------------
 1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/drivers/thermal/broadcom/bcm2835_thermal.c b/drivers/thermal/broadcom/bcm2835_thermal.c
index 5c1cebe07580..3b1030fc4fbf 100644
--- a/drivers/thermal/broadcom/bcm2835_thermal.c
+++ b/drivers/thermal/broadcom/bcm2835_thermal.c
@@ -185,7 +185,7 @@ 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)
@@ -193,10 +193,6 @@ static int bcm2835_thermal_probe(struct platform_device *pdev)
 		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 */
@@ -269,17 +265,11 @@ 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)
@@ -287,7 +277,6 @@ 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 = {

-- 
2.43.0