thermal: core: Rewrite comments in handle_thermal_trip()

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@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index fc6ff0a4faa1d1537a737ced1def1decd0fc7ae1..c4bc7973a6cd338113341a8bb562711f08b449fa 100644 (file)
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -368,6 +368,13 @@ static void handle_thermal_trip(struct thermal_zone_device *tz,
        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 thermal_zone_device *tz,
                        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 thermal_zone_device *tz,
                }
        } 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);