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From:   "Rafael J. Wysocki" <rjw@rjwysocki.net>
To:     Linux ACPI <linux-acpi@vger.kernel.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        Michal Wilczynski <michal.wilczynski@intel.com>,
        Zhang Rui <rui.zhang@intel.com>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>
Subject: [PATCH v1 6/7] ACPI: thermal: Rework thermal_get_trend()
Date:   Tue, 18 Jul 2023 20:07:49 +0200
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From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Rework the ACPI thermal driver's .get_trend() callback function,
thermal_get_trend(), to use trip point data stored in the generic
trip structures instead of calling thermal_get_trip_type() and
thermal_get_trip_temp() and make it hold thermal_check_lock to
protect against possible races against trip point updates.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/thermal.c |  107 +++++++++++++++++++++++++++++++++++--------------
 1 file changed, 78 insertions(+), 29 deletions(-)

Index: linux-pm/drivers/acpi/thermal.c
===================================================================
--- linux-pm.orig/drivers/acpi/thermal.c
+++ linux-pm/drivers/acpi/thermal.c
@@ -572,47 +572,96 @@ static int thermal_get_crit_temp(struct
 	return -EINVAL;
 }
 
+static struct thermal_trip *acpi_thermal_get_trip(struct acpi_thermal *tz,
+					   int trip_index)
+{
+	struct thermal_trip *trip;
+	int i;
+
+	if (!tz || trip_index < 0)
+		return NULL;
+
+	trip = tz->trips.critical.trip_ref.trip;
+	if (trip) {
+		if (!trip_index)
+			return trip;
+
+		trip_index--;
+	}
+
+	trip = tz->trips.hot.trip_ref.trip;
+	if (trip) {
+		if (!trip_index)
+			return trip;
+
+		trip_index--;
+	}
+
+	trip = tz->trips.passive.trip_ref.trip;
+	if (trip) {
+		if (!trip_index)
+			return trip;
+
+		trip_index--;
+	}
+
+	for (i = 0; i < ACPI_THERMAL_MAX_ACTIVE; i++) {
+		trip = tz->trips.active[i].trip_ref.trip;
+		if (trip) {
+			if (!trip_index)
+				return trip;
+
+			trip_index--;
+		}
+	}
+
+	return NULL;
+}
+
 static int thermal_get_trend(struct thermal_zone_device *thermal,
-			     int trip, enum thermal_trend *trend)
+			     int trip_index, enum thermal_trend *trend)
 {
 	struct acpi_thermal *tz = thermal_zone_device_priv(thermal);
-	enum thermal_trip_type type;
-	int i;
+	struct thermal_trip *trip;
+	int ret = 0;
 
-	if (thermal_get_trip_type(thermal, trip, &type))
-		return -EINVAL;
+	mutex_lock(&tz->thermal_check_lock);
 
-	if (type == THERMAL_TRIP_ACTIVE) {
-		int trip_temp;
+	trip = acpi_thermal_get_trip(tz, trip_index);
+	if (!trip) {
+		ret = -EINVAL;
+		goto out;
+	}
+	if (trip->type == THERMAL_TRIP_ACTIVE) {
 		int temp = deci_kelvin_to_millicelsius_with_offset(
 					tz->temperature, tz->kelvin_offset);
-		if (thermal_get_trip_temp(thermal, trip, &trip_temp))
-			return -EINVAL;
 
-		if (temp > trip_temp) {
+		if (temp > trip->temperature)
 			*trend = THERMAL_TREND_RAISING;
-			return 0;
-		} else {
-			/* Fall back on default trend */
-			return -EINVAL;
-		}
+		else /* Fall back on default trend */
+			ret = -EINVAL;
+	} else {
+		/*
+		 * tz->temperature has already been updated by generic thermal
+		 * layer, before this callback being invoked.
+		 */
+		int i = tz->trips.passive.tc1 * (tz->temperature -
+				tz->last_temperature) +
+			tz->trips.passive.tc2 * (tz->temperature -
+				tz->trips.passive.temperature);
+
+		if (i > 0)
+			*trend = THERMAL_TREND_RAISING;
+		else if (i < 0)
+			*trend = THERMAL_TREND_DROPPING;
+		else
+			*trend = THERMAL_TREND_STABLE;
 	}
 
-	/*
-	 * tz->temperature has already been updated by generic thermal layer,
-	 * before this callback being invoked
-	 */
-	i = tz->trips.passive.tc1 * (tz->temperature - tz->last_temperature) +
-	    tz->trips.passive.tc2 * (tz->temperature - tz->trips.passive.temperature);
-
-	if (i > 0)
-		*trend = THERMAL_TREND_RAISING;
-	else if (i < 0)
-		*trend = THERMAL_TREND_DROPPING;
-	else
-		*trend = THERMAL_TREND_STABLE;
+out:
+	mutex_unlock(&tz->thermal_check_lock);
 
-	return 0;
+	return ret;
 }
 
 static void acpi_thermal_zone_device_hot(struct thermal_zone_device *thermal)