linux-kernel - [PATCH v1] thermal/of: Fix cdev lookup in thermal_of_should

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Message-ID: <2788228.mvXUDI8C0e@rjwysocki.net>
Date: Fri, 21 Feb 2025 17:57:11 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Lukasz Luba <lukasz.luba@....com>,
 Daniel Lezcano <daniel.lezcano@...aro.org>, Yu-Che Cheng <giver@...omium.org>
Subject: [PATCH v1] thermal/of: Fix cdev lookup in thermal_of_should_bind()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Since thermal_of_should_bind() terminates the loop after processing
the first child found in cooling-maps, it will never match more than
one cdev to a given trip point which is incorrect, as there may be
cooling-maps associating one trip point with multiple cooling devices.

Address this by letting the loop continue until either all
children have been processed or a matching one has been found.

To avoid adding conditionals or goto statements, put the loop in
question into a separate function and make that function return
right away after finding a matching cooling-maps entry.

Fixes: 94c6110b0b13 ("thermal/of: Use the .should_bind() thermal zone callback")
Link: https://lore.kernel.org/linux-pm/20250219-fix-thermal-of-v1-1-de36e7a590c4@chromium.org/
Reported-by: Yu-Che Cheng <giver@...omium.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/thermal/thermal_of.c |   50 ++++++++++++++++++++++++-------------------
 1 file changed, 29 insertions(+), 21 deletions(-)

--- a/drivers/thermal/thermal_of.c
+++ b/drivers/thermal/thermal_of.c
@@ -274,6 +274,34 @@
 	return true;
 }

+static bool thermal_of_cm_lookup(struct device_node *cm_np,
+				 const struct thermal_trip *trip,
+				 struct thermal_cooling_device *cdev,
+				 struct cooling_spec *c)
+{
+	for_each_child_of_node_scoped(cm_np, child) {
+		struct device_node *tr_np;
+		int count, i;
+
+		tr_np = of_parse_phandle(child, "trip", 0);
+		if (tr_np != trip->priv)
+			continue;
+
+		/* The trip has been found, look up the cdev. */
+		count = of_count_phandle_with_args(child, "cooling-device",
+						   "#cooling-cells");
+		if (count <= 0)
+			pr_err("Add a cooling_device property with at least one device\n");
+
+		for (i = 0; i < count; i++) {
+			if (thermal_of_get_cooling_spec(child, i, cdev, c))
+				return true;
+		}
+	}
+
+	return false;
+}
+
 static bool thermal_of_should_bind(struct thermal_zone_device *tz,
 				   const struct thermal_trip *trip,
 				   struct thermal_cooling_device *cdev,
@@ -293,27 +321,7 @@
 		goto out;

 	/* Look up the trip and the cdev in the cooling maps. */
-	for_each_child_of_node_scoped(cm_np, child) {
-		struct device_node *tr_np;
-		int count, i;
-
-		tr_np = of_parse_phandle(child, "trip", 0);
-		if (tr_np != trip->priv)
-			continue;
-
-		/* The trip has been found, look up the cdev. */
-		count = of_count_phandle_with_args(child, "cooling-device", "#cooling-cells");
-		if (count <= 0)
-			pr_err("Add a cooling_device property with at least one device\n");
-
-		for (i = 0; i < count; i++) {
-			result = thermal_of_get_cooling_spec(child, i, cdev, c);
-			if (result)
-				break;
-		}
-
-		break;
-	}
+	result = thermal_of_cm_lookup(cm_np, trip, cdev, c);

 	of_node_put(cm_np);
 out: