thermal: core: Sort trip point crossing notifications by temperature

If multiple trip points are crossed in one go and the trips table in
the thermal zone device object is not sorted, the corresponding trip
point crossing notifications sent to user space will not be ordered
either.

Moreover, if the trips table is sorted by trip temperature in ascending
order, the trip crossing notifications on the way up will be sent in that
order too, but the trip crossing notifications on the way down will be
sent in the reverse order.

This is generally confusing and it is better to make the kernel send the
notifications in the order of growing (on the way up) or falling (on the
way down) trip temperature.

To achieve that, instead of sending a trip crossing notification and
recording a trip crossing event in the statistics right away from
handle_thermal_trip(), put the trip in question on a list that will be
sorted by __thermal_zone_device_update() after processing all of the trips
and before sending the notifications and recording trip crossing events.

Link: https://lore.kernel.org/linux-pm/20240306085428.88011-1-daniel.lezcano@linaro.org/
Reported-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>

Author: rafaeljw

drivers/thermal/thermal_core.c

@@ -15,6 +15,7 @@
 #include <linux/slab.h>
 #include <linux/kdev_t.h>
 #include <linux/idr.h>
+#include <linux/list_sort.h>
 #include <linux/thermal.h>
 #include <linux/reboot.h>
 #include <linux/string.h>
@@ -361,7 +362,9 @@ static void handle_critical_trips(struct thermal_zone_device *tz,
 }
 
 static void handle_thermal_trip(struct thermal_zone_device *tz,
-				struct thermal_trip_desc *td)
+				struct thermal_trip_desc *td,
+				struct list_head *way_up_list,
+				struct list_head *way_down_list)
 {
 	const struct thermal_trip *trip = &td->trip;
 	int old_threshold;
@@ -387,8 +390,8 @@ static void handle_thermal_trip(struct thermal_zone_device *tz,
 		 * In that case, the trip temperature becomes the new threshold.
 		 */
 		if (tz->temperature < trip->temperature - trip->hysteresis) {
-			thermal_notify_tz_trip_down(tz, trip);
-			thermal_debug_tz_trip_down(tz, trip);
+			list_add(&td->notify_list_node, way_down_list);
+			td->notify_temp = trip->temperature - trip->hysteresis;
 		} else {
 			td->threshold -= trip->hysteresis;
 		}
@@ -398,8 +401,8 @@ static void handle_thermal_trip(struct thermal_zone_device *tz,
 		 * if the zone temperature exceeds the trip one.  The new
 		 * threshold is then set to the low temperature of the trip.
 		 */
-		thermal_notify_tz_trip_up(tz, trip);
-		thermal_debug_tz_trip_up(tz, trip);
+		list_add_tail(&td->notify_list_node, way_up_list);
+		td->notify_temp = trip->temperature;
 		td->threshold -= trip->hysteresis;
 	}
 
@@ -452,10 +455,24 @@ static void thermal_zone_device_init(struct thermal_zone_device *tz)
 		pos->initialized = false;
 }
 
+static int thermal_trip_notify_cmp(void *ascending, const struct list_head *a,
+				   const struct list_head *b)
+{
+	struct thermal_trip_desc *tda = container_of(a, struct thermal_trip_desc,
+						     notify_list_node);
+	struct thermal_trip_desc *tdb = container_of(b, struct thermal_trip_desc,
+						     notify_list_node);
+	int ret = tdb->notify_temp - tda->notify_temp;
+
+	return ascending ? ret : -ret;
+}
+
 void __thermal_zone_device_update(struct thermal_zone_device *tz,
 				  enum thermal_notify_event event)
 {
 	struct thermal_trip_desc *td;
+	LIST_HEAD(way_down_list);
+	LIST_HEAD(way_up_list);
 
 	if (tz->suspended)
 		return;
@@ -470,7 +487,19 @@ void __thermal_zone_device_update(struct thermal_zone_device *tz,
 	tz->notify_event = event;
 
 	for_each_trip_desc(tz, td)
-		handle_thermal_trip(tz, td);
+		handle_thermal_trip(tz, td, &way_up_list, &way_down_list);
+
+	list_sort(&way_up_list, &way_up_list, thermal_trip_notify_cmp);
+	list_for_each_entry(td, &way_up_list, notify_list_node) {
+		thermal_notify_tz_trip_up(tz, &td->trip);
+		thermal_debug_tz_trip_up(tz, &td->trip);
+	}
+
+	list_sort(NULL, &way_down_list, thermal_trip_notify_cmp);
+	list_for_each_entry(td, &way_down_list, notify_list_node) {
+		thermal_notify_tz_trip_down(tz, &td->trip);
+		thermal_debug_tz_trip_down(tz, &td->trip);
+	}
 
 	monitor_thermal_zone(tz);
 }

drivers/thermal/thermal_core.h

@@ -17,6 +17,8 @@
 
 struct thermal_trip_desc {
 	struct thermal_trip trip;
+	struct list_head notify_list_node;
+	int notify_temp;
 	int threshold;
 };