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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Linux PM <linux-pm@vger.kernel.org>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>,
 LKML <linux-kernel@vger.kernel.org>, Linux ACPI <linux-acpi@vger.kernel.org>,
 Lukasz Luba <lukasz.luba@arm.com>, Zhang Rui <rui.zhang@intel.com>,
 Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
 Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Subject:
 [PATCH v1 2/6] thermal: ACPI: Discard trip table after zone registration
Date: Mon, 05 Feb 2024 22:15:50 +0100
Message-ID: <4905992.31r3eYUQgx@kreacher>
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From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Because the thermal core creates and uses its own copy of the trips
table passed to thermal_zone_device_register_with_trips(), it is not
necessary to hold on to a local copy of it any more after the given
thermal zone has been registered.

Accordingly, modify the ACPI thermal driver to store the trips table
passed to thermal_zone_device_register_with_trips() in a local variable
which is automatically discarded after the zone registration.

Also make some additional code simplifications unlocked by the above
change.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/thermal.c |   57 +++++++++++++++++--------------------------------
 1 file changed, 20 insertions(+), 37 deletions(-)

Index: linux-pm/drivers/acpi/thermal.c
===================================================================
--- linux-pm.orig/drivers/acpi/thermal.c
+++ linux-pm/drivers/acpi/thermal.c
@@ -47,6 +47,8 @@
 
 #define ACPI_THERMAL_TRIP_PASSIVE	(-1)
 
+#define ACPI_THERMAL_MAX_NR_TRIPS	(ACPI_THERMAL_MAX_ACTIVE + 3)
+
 /*
  * This exception is thrown out in two cases:
  * 1.An invalid trip point becomes invalid or a valid trip point becomes invalid
@@ -112,7 +114,6 @@ struct acpi_thermal {
 	unsigned long polling_frequency;
 	volatile u8 zombie;
 	struct acpi_thermal_trips trips;
-	struct thermal_trip *trip_table;
 	struct thermal_zone_device *thermal_zone;
 	int kelvin_offset;	/* in millidegrees */
 	struct work_struct thermal_check_work;
@@ -451,26 +452,19 @@ fail:
 	return false;
 }
 
-static int acpi_thermal_get_trip_points(struct acpi_thermal *tz)
+static void acpi_thermal_get_trip_points(struct acpi_thermal *tz)
 {
-	unsigned int count = 0;
 	int i;
 
-	if (acpi_thermal_init_trip(tz, ACPI_THERMAL_TRIP_PASSIVE))
-		count++;
+	acpi_thermal_init_trip(tz, ACPI_THERMAL_TRIP_PASSIVE);
 
 	for (i = 0; i < ACPI_THERMAL_MAX_ACTIVE; i++) {
-		if (acpi_thermal_init_trip(tz, i))
-			count++;
-		else
+		if (!acpi_thermal_init_trip(tz, i))
 			break;
-
 	}
 
 	while (++i < ACPI_THERMAL_MAX_ACTIVE)
 		tz->trips.active[i].trip.temp_dk = THERMAL_TEMP_INVALID;
-
-	return count;
 }
 
 /* sys I/F for generic thermal sysfs support */
@@ -662,13 +656,14 @@ static void acpi_thermal_zone_sysfs_remo
 }
 
 static int acpi_thermal_register_thermal_zone(struct acpi_thermal *tz,
+					      const struct thermal_trip *trip_table,
 					      unsigned int trip_count,
 					      int passive_delay)
 {
 	int result;
 
 	tz->thermal_zone = thermal_zone_device_register_with_trips("acpitz",
-								   tz->trip_table,
+								   trip_table,
 								   trip_count,
 								   0, tz,
 								   &acpi_thermal_zone_ops,
@@ -823,10 +818,10 @@ static void acpi_thermal_free_thermal_zo
 
 static int acpi_thermal_add(struct acpi_device *device)
 {
+	struct thermal_trip trip_table[ACPI_THERMAL_MAX_NR_TRIPS] = { 0 };
 	struct acpi_thermal_trip *acpi_trip;
 	struct thermal_trip *trip;
 	struct acpi_thermal *tz;
-	unsigned int trip_count;
 	int crit_temp, hot_temp;
 	int passive_delay = 0;
 	int result;
@@ -848,21 +843,10 @@ static int acpi_thermal_add(struct acpi_
 	acpi_thermal_aml_dependency_fix(tz);
 
 	/* Get trip points [_CRT, _PSV, etc.] (required). */
-	trip_count = acpi_thermal_get_trip_points(tz);
+	acpi_thermal_get_trip_points(tz);
 
 	crit_temp = acpi_thermal_get_critical_trip(tz);
-	if (crit_temp != THERMAL_TEMP_INVALID)
-		trip_count++;
-
 	hot_temp = acpi_thermal_get_hot_trip(tz);
-	if (hot_temp != THERMAL_TEMP_INVALID)
-		trip_count++;
-
-	if (!trip_count) {
-		pr_warn(FW_BUG "No valid trip points!\n");
-		result = -ENODEV;
-		goto free_memory;
-	}
 
 	/* Get temperature [_TMP] (required). */
 	result = acpi_thermal_get_temperature(tz);
@@ -881,13 +865,7 @@ static int acpi_thermal_add(struct acpi_
 
 	acpi_thermal_guess_offset(tz, crit_temp);
 
-	trip = kcalloc(trip_count, sizeof(*trip), GFP_KERNEL);
-	if (!trip) {
-		result = -ENOMEM;
-		goto free_memory;
-	}
-
-	tz->trip_table = trip;
+	trip = trip_table;
 
 	if (crit_temp != THERMAL_TEMP_INVALID) {
 		trip->type = THERMAL_TRIP_CRITICAL;
@@ -923,9 +901,17 @@ static int acpi_thermal_add(struct acpi_
 		trip++;
 	}
 
-	result = acpi_thermal_register_thermal_zone(tz, trip_count, passive_delay);
+	if (trip == trip_table) {
+		pr_warn(FW_BUG "No valid trip points!\n");
+		result = -ENODEV;
+		goto free_memory;
+	}
+
+	result = acpi_thermal_register_thermal_zone(tz, trip_table,
+						    trip - trip_table,
+						    passive_delay);
 	if (result)
-		goto free_trips;
+		goto free_memory;
 
 	refcount_set(&tz->thermal_check_count, 3);
 	mutex_init(&tz->thermal_check_lock);
@@ -944,8 +930,6 @@ static int acpi_thermal_add(struct acpi_
 flush_wq:
 	flush_workqueue(acpi_thermal_pm_queue);
 	acpi_thermal_unregister_thermal_zone(tz);
-free_trips:
-	kfree(tz->trip_table);
 free_memory:
 	acpi_thermal_free_thermal_zone(tz);
 
@@ -966,7 +950,6 @@ static void acpi_thermal_remove(struct a
 
 	flush_workqueue(acpi_thermal_pm_queue);
 	acpi_thermal_unregister_thermal_zone(tz);
-	kfree(tz->trip_table);
 	acpi_thermal_free_thermal_zone(tz);
 }