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From:   Daniel Lezcano <daniel.lezcano@linaro.org>
To:     rafael@kernel.org, daniel.lezcano@linaro.org
Cc:     Amit Kucheria <amitk@kernel.org>, Zhang Rui <rui.zhang@intel.com>,
        linux-pm@vger.kernel.org (open list:THERMAL),
        linux-kernel@vger.kernel.org (open list)
Subject: [RFC PATCH] thermal/core: Update the generic trip points
Date:   Fri, 14 Apr 2023 01:13:18 +0200
Message-Id: <20230413231318.143135-1-daniel.lezcano@linaro.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

At this point, the generic trip points rework allows to create a
thermal zone with a fixed number of trip points. This usage satisfy
almost all of the existing drivers.

A few remaining drivers have a mechanism where the firmware updates
the trip points. But there is no such update mechanism for the generic
trip points, thus those drivers can not be converted to the generic
approach.

This patch provides a function 'thermal_zone_trips_update()' allowing
to change the trip points of a thermal zone.

At the same time, with the logic the trip points array is passed as a
parameter to the thermal zone at creation time, we make our own
private trip points array by copying the one passed as parameter.

Note, no code has been found where the trip points update leads to a
refresh of the trip points in sysfs, so it is very unlikey the number
of trip points changes. However, for the sake of consistency it would
be nicer to have the trip points being refreshed in sysfs also, but
that could be done in a separate set of changes.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/thermal/thermal_core.c | 40 ++++++++----------
 drivers/thermal/thermal_core.h |  3 ++
 drivers/thermal/thermal_trip.c | 76 ++++++++++++++++++++++++++++++++++
 include/linux/thermal.h        |  4 ++
 4 files changed, 100 insertions(+), 23 deletions(-)

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index afcd4197babd..3688b06401c8 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -1224,32 +1224,11 @@ thermal_zone_device_register_with_trips(const char *type, struct thermal_trip *t
 		return ERR_PTR(-EINVAL);
 	}
 
-	/*
-	 * Max trip count can't exceed 31 as the "mask >> num_trips" condition.
-	 * For example, shifting by 32 will result in compiler warning:
-	 * warning: right shift count >= width of type [-Wshift-count- overflow]
-	 *
-	 * Also "mask >> num_trips" will always be true with 32 bit shift.
-	 * E.g. mask = 0x80000000 for trip id 31 to be RW. Then
-	 * mask >> 32 = 0x80000000
-	 * This will result in failure for the below condition.
-	 *
-	 * Check will be true when the bit 31 of the mask is set.
-	 * 32 bit shift will cause overflow of 4 byte integer.
-	 */
-	if (num_trips > (BITS_PER_TYPE(int) - 1) || num_trips < 0 || mask >> num_trips) {
-		pr_err("Incorrect number of thermal trips\n");
-		return ERR_PTR(-EINVAL);
-	}
-
 	if (!ops) {
 		pr_err("Thermal zone device ops not defined\n");
 		return ERR_PTR(-EINVAL);
 	}
 
-	if (num_trips > 0 && (!ops->get_trip_type || !ops->get_trip_temp) && !trips)
-		return ERR_PTR(-EINVAL);
-
 	if (!thermal_class)
 		return ERR_PTR(-ENODEV);
 
@@ -1283,8 +1262,22 @@ thermal_zone_device_register_with_trips(const char *type, struct thermal_trip *t
 	tz->ops = ops;
 	tz->device.class = thermal_class;
 	tz->devdata = devdata;
-	tz->trips = trips;
-	tz->num_trips = num_trips;
+
+	if (trips) {
+		result = __thermal_zone_trips_update(tz, trips, num_trips, mask);
+		if (result)
+			goto remove_id;
+	} else {
+		/*
+		 * Legacy trip point handling
+		 */
+		if ((!tz->ops->get_trip_type || !tz->ops->get_trip_temp) && num_trips) {
+			result = -EINVAL;
+			goto remove_id;
+		}
+
+		tz->num_trips = num_trips;
+	}
 
 	thermal_set_delay_jiffies(&tz->passive_delay_jiffies, passive_delay);
 	thermal_set_delay_jiffies(&tz->polling_delay_jiffies, polling_delay);
@@ -1451,6 +1444,7 @@ void thermal_zone_device_unregister(struct thermal_zone_device *tz)
 	mutex_unlock(&tz->lock);
 
 	kfree(tz->tzp);
+	kfree(tz->trips);
 
 	put_device(&tz->device);
 
diff --git a/drivers/thermal/thermal_core.h b/drivers/thermal/thermal_core.h
index d9182fb8dd11..9fc7d9e9debd 100644
--- a/drivers/thermal/thermal_core.h
+++ b/drivers/thermal/thermal_core.h
@@ -203,6 +203,9 @@ void __thermal_zone_device_update(struct thermal_zone_device *tz,
 void __thermal_zone_set_trips(struct thermal_zone_device *tz);
 int __thermal_zone_get_trip(struct thermal_zone_device *tz, int trip_id,
 			    struct thermal_trip *trip);
+int __thermal_zone_trips_update(struct thermal_zone_device *tz,
+				struct thermal_trip *trips,
+				int num_trips, int mask);
 int __thermal_zone_get_temp(struct thermal_zone_device *tz, int *temp);
 
 /* sysfs I/F */
diff --git a/drivers/thermal/thermal_trip.c b/drivers/thermal/thermal_trip.c
index a12980a8bac5..e05384c3e557 100644
--- a/drivers/thermal/thermal_trip.c
+++ b/drivers/thermal/thermal_trip.c
@@ -227,3 +227,79 @@ int thermal_zone_set_trip(struct thermal_zone_device *tz, int trip_id,
 
 	return 0;
 }
+
+int __thermal_zone_trips_update(struct thermal_zone_device *tz, struct thermal_trip *trips,
+				int num_trips, int mask)
+{
+	struct thermal_trip *new_trips;
+
+	/*
+	 * Legacy trip point handling is incompatible with this
+	 * function
+	 */
+	if (tz->ops->get_trip_type || tz->ops->get_trip_temp) {
+		pr_err("Legacy trip points use incompatible function '%s'\n", __func__);
+		return -ENOSYS;
+	}
+	
+	/*
+	 * Max trip count can't exceed 31 as the "mask >> num_trips" condition.
+	 * For example, shifting by 32 will result in compiler warning:
+	 * warning: right shift count >= width of type [-Wshift-count- overflow]
+	 *
+	 * Also "mask >> num_trips" will always be true with 32 bit shift.
+	 * E.g. mask = 0x80000000 for trip id 31 to be RW. Then
+	 * mask >> 32 = 0x80000000
+	 * This will result in failure for the below condition.
+	 *
+	 * Check will be true when the bit 31 of the mask is set.
+	 * 32 bit shift will cause overflow of 4 byte integer.
+	 */
+	if (num_trips > (BITS_PER_TYPE(int) - 1) || num_trips < 0 || mask >> num_trips) {
+		pr_err("Incorrect number of thermal trips\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * New generic trip point handling
+	 */
+	if (num_trips > 0 && !trips) {
+		pr_err("Inconsistent parameters\n");
+		return -EINVAL;
+	}
+
+	/*
+	 * Allocate our private trip points array structure
+	 */
+	new_trips = kmemdup(trips, sizeof(*trips) * num_trips, GFP_KERNEL);
+	if (!new_trips)
+		return -ENOMEM;
+	
+	/*
+	 * Newly allocated thermal zone will have the 'trips' field
+	 * NULL, kfree() is immune against that
+	 */
+	kfree(tz->trips);
+	tz->trips = new_trips;
+	tz->num_trips = num_trips;
+
+	return 0;
+}
+
+int thermal_zone_trips_update(struct thermal_zone_device *tz, struct thermal_trip *trips,
+			      int num_trips, int mask)
+{
+	int ret;
+
+	mutex_lock(&tz->lock);
+	ret = __thermal_zone_trips_update(tz, trips, num_trips, mask);
+	mutex_unlock(&tz->lock);
+
+	if (ret)
+		return ret;
+
+	__thermal_zone_device_update(tz, THERMAL_TRIP_CHANGED);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(thermal_zone_trips_update);
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index 3e8bedb21755..0ea2da5c33ac 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -216,6 +216,10 @@ int thermal_zone_get_num_trips(struct thermal_zone_device *tz);
 
 int thermal_zone_get_crit_temp(struct thermal_zone_device *tz, int *temp);
 
+int thermal_zone_trips_update(struct thermal_zone_device *tz,
+			      struct thermal_trip *trips,
+			      int num_trips, int mask);
+
 #ifdef CONFIG_THERMAL_ACPI
 int thermal_acpi_active_trip_temp(struct acpi_device *adev, int id, int *ret_temp);
 int thermal_acpi_passive_trip_temp(struct acpi_device *adev, int *ret_temp);
-- 
2.34.1