thermal/thresholds: Fix boundaries and detection routine

The current implementation does not work if the thermal zone is
interrupt driven only.

The boundaries are not correctly checked and computed as it happens
only when the temperature is increasing or decreasing.

The problem arises because the routine to detect when we cross a
threshold is correlated with the computation of the boundaries. We
assume we have to recompute the boundaries when a threshold is crossed
but actually we should do that even if the it is not the case.

Mixing the boundaries computation and the threshold detection for the
sake of optimizing the routine is much more complex as it appears
intuitively and prone to errors.

This fix separates the boundaries computation and the threshold
crossing detection into different routines. The result is a code much
more simple to understand, thus easier to maintain.

The drawback is we browse the thresholds list several time but we can
consider that as neglictible because that happens when the temperature
is updated. There are certainly some aeras to improve in the
temperature update routine but it would be not adequate as this change
aims to fix the thresholds for v6.13.

Fixes: 445936f ("thermal: core: Add user thresholds support")
Tested-by: Daniel Lezcano <daniel.lezcano@linaro.org> # rock5b, Lenovo x13s
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://patch.msgid.link/20241216212644.1145122-1-daniel.lezcano@linaro.org
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: dlezcano

drivers/thermal/thermal_thresholds.c

@@ -69,58 +69,60 @@ static struct user_threshold *__thermal_thresholds_find(const struct list_head *
 	return NULL;
 }
 
-static bool __thermal_threshold_is_crossed(struct user_threshold *threshold, int temperature,
-					   int last_temperature, int direction,
-					   int *low, int *high)
+static bool thermal_thresholds_handle_raising(struct list_head *thresholds, int temperature,
+					      int last_temperature)
 {
+	struct user_threshold *t;
 
-	if (temperature >= threshold->temperature) {
-		if (threshold->temperature > *low &&
-		    THERMAL_THRESHOLD_WAY_DOWN & threshold->direction)
-			*low = threshold->temperature;
+	list_for_each_entry(t, thresholds, list_node) {
 
-		if (last_temperature < threshold->temperature &&
-		    threshold->direction & direction)
-			return true;
-	} else {
-		if (threshold->temperature < *high && THERMAL_THRESHOLD_WAY_UP
-		    & threshold->direction)
-			*high = threshold->temperature;
+		if (!(t->direction & THERMAL_THRESHOLD_WAY_UP))
+		    continue;
 
-		if (last_temperature >= threshold->temperature &&
-		    threshold->direction & direction)
+		if (temperature >= t->temperature &&
+		    last_temperature < t->temperature)
 			return true;
 	}
 
 	return false;
 }
 
-static bool thermal_thresholds_handle_raising(struct list_head *thresholds, int temperature,
-					      int last_temperature, int *low, int *high)
+static bool thermal_thresholds_handle_dropping(struct list_head *thresholds, int temperature,
+					       int last_temperature)
 {
 	struct user_threshold *t;
 
-	list_for_each_entry(t, thresholds, list_node) {
-		if (__thermal_threshold_is_crossed(t, temperature, last_temperature,
-						   THERMAL_THRESHOLD_WAY_UP, low, high))
+	list_for_each_entry_reverse(t, thresholds, list_node) {
+
+		if (!(t->direction & THERMAL_THRESHOLD_WAY_DOWN))
+		    continue;
+
+		if (temperature <= t->temperature &&
+		    last_temperature > t->temperature)
 			return true;
 	}
 
 	return false;
 }
 
-static bool thermal_thresholds_handle_dropping(struct list_head *thresholds, int temperature,
-					       int last_temperature, int *low, int *high)
+static void thermal_threshold_find_boundaries(struct list_head *thresholds, int temperature,
+					      int *low, int *high)
 {
 	struct user_threshold *t;
 
-	list_for_each_entry_reverse(t, thresholds, list_node) {
-		if (__thermal_threshold_is_crossed(t, temperature, last_temperature,
-						   THERMAL_THRESHOLD_WAY_DOWN, low, high))
-			return true;
+	list_for_each_entry(t, thresholds, list_node) {
+		if (temperature < t->temperature &&
+		    (t->direction & THERMAL_THRESHOLD_WAY_UP) &&
+		    *high > t->temperature)
+			*high = t->temperature;
 	}
 
-	return false;
+	list_for_each_entry_reverse(t, thresholds, list_node) {
+		if (temperature > t->temperature &&
+		    (t->direction & THERMAL_THRESHOLD_WAY_DOWN) &&
+		    *low < t->temperature)
+			*low = t->temperature;
+	}
 }
 
 void thermal_thresholds_handle(struct thermal_zone_device *tz, int *low, int *high)
@@ -132,6 +134,8 @@ void thermal_thresholds_handle(struct thermal_zone_device *tz, int *low, int *hi
 
 	lockdep_assert_held(&tz->lock);
 
+	thermal_threshold_find_boundaries(thresholds, temperature, low, high);
+
 	/*
 	 * We need a second update in order to detect a threshold being crossed
 	 */
@@ -151,12 +155,12 @@ void thermal_thresholds_handle(struct thermal_zone_device *tz, int *low, int *hi
 	 * - decreased : thresholds are crossed the way down
 	 */
 	if (temperature > last_temperature) {
-		if (thermal_thresholds_handle_raising(thresholds, temperature,
-						      last_temperature, low, high))
+		if (thermal_thresholds_handle_raising(thresholds,
+						      temperature, last_temperature))
 			thermal_notify_threshold_up(tz);
 	} else {
-		if (thermal_thresholds_handle_dropping(thresholds, temperature,
-						       last_temperature, low, high))
+		if (thermal_thresholds_handle_dropping(thresholds,
+						       temperature, last_temperature))
 			thermal_notify_threshold_down(tz);
 	}
 }