linux-kernel - [PATCH v3 3/6] thermal: core: Rewrite comments in handle_thermal

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Date: Tue, 02 Apr 2024 20:59:01 +0200
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
 Daniel Lezcano <daniel.lezcano@...aro.org>,
 Lukasz Luba <lukasz.luba@....com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Subject:
 [PATCH v3 3/6] thermal: core: Rewrite comments in handle_thermal_trip()

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

Make the comments regarding trip crossing and threshold updates in
handle_thermal_trip() slightly more clear.

No functional impact.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---

v2 -> v3: New patch

---
 drivers/thermal/thermal_core.c |   26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

Index: linux-pm/drivers/thermal/thermal_core.c
===================================================================
--- linux-pm.orig/drivers/thermal/thermal_core.c
+++ linux-pm/drivers/thermal/thermal_core.c
@@ -368,6 +368,13 @@ static void handle_thermal_trip(struct t
 	if (trip->temperature == THERMAL_TEMP_INVALID)
 		return;
 
+	/*
+	 * If the trip temperature or hysteresis has been updated recently,
+	 * the threshold needs to be computed again using the new values.
+	 * However, its initial value still reflects the old ones and that
+	 * is what needs to be compared with the previous zone temperature
+	 * to decide which action to take.
+	 */
 	if (tz->last_temperature == THERMAL_TEMP_INVALID) {
 		/* Initialization. */
 		td->threshold = trip->temperature;
@@ -375,11 +382,9 @@ static void handle_thermal_trip(struct t
 			td->threshold -= trip->hysteresis;
 	} else if (tz->last_temperature < td->threshold) {
 		/*
-		 * The trip threshold is equal to the trip temperature, unless
-		 * the latter has changed in the meantime.  In either case,
-		 * the trip is crossed if the current zone temperature is at
-		 * least equal to its temperature, but otherwise ensure that
-		 * the threshold and the trip temperature will be equal.
+		 * There is no mitigation under way, so it needs to be started
+		 * if the zone temperature exceeds the trip one.  The new
+		 * threshold is then set to the low temperature of the trip.
 		 */
 		if (tz->temperature >= trip->temperature) {
 			thermal_notify_tz_trip_up(tz, trip);
@@ -390,14 +395,9 @@ static void handle_thermal_trip(struct t
 		}
 	} else {
 		/*
-		 * The previous zone temperature was above or equal to the trip
-		 * threshold, which would be equal to the "low temperature" of
-		 * the trip (its temperature minus its hysteresis), unless the
-		 * trip temperature or hysteresis had changed.  In either case,
-		 * the trip is crossed if the current zone temperature is below
-		 * the low temperature of the trip, but otherwise ensure that
-		 * the trip threshold will be equal to the low temperature of
-		 * the trip.
+		 * Mitigation is under way, so it needs to stop if the zone
+		 * temperature falls below the low temperature of the trip.
+		 * In that case, the trip temperature becomes the new threshold.
 		 */
 		if (tz->temperature < trip->temperature - trip->hysteresis) {
 			thermal_notify_tz_trip_down(tz, trip);