Message-Id: <20250410165456.4173-4-W_Armin@gmx.de>
Date: Thu, 10 Apr 2025 18:54:56 +0200
From: Armin Wolf <W_Armin@....de>
To: rafael@...nel.org,
	rui.zhang@...el.com
Cc: lenb@...nel.org,
	linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] ACPI: thermal: Allow userspace applications to change the cooling mode

Users might want to signal the ACPI firmware whether active or passive
cooling is preferred. This is already possible under Windows using the
Windows power settings.

Add a new "cooling_mode" sysfs attribute which can be used by users to
change the cooling mode of a given thermal zone. Only thermal zones
supporting the _SCP control method will expose this new attribute.

Signed-off-by: Armin Wolf <W_Armin@....de>
---
 .../ABI/testing/sysfs-driver-thermal          |  14 ++
 MAINTAINERS                                   |   1 +
 drivers/acpi/thermal.c                        | 129 ++++++++++++++++--
 3 files changed, 132 insertions(+), 12 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-driver-thermal

diff --git a/Documentation/ABI/testing/sysfs-driver-thermal b/Documentation/ABI/testing/sysfs-driver-thermal
new file mode 100644
index 000000000000..bf2349f31863
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-thermal
@@ -0,0 +1,14 @@
+What:		/sys/bus/acpi/devices/LNXTHERM:*/cooling_mode
+Date:		April 2025
+KernelVersion:	6.16
+Contact:	Armin Wolf <W_Armin@....de>
+Description:
+		A string representing the preferred cooling mode of the
+		associated ACPI thermal zone:
+
+		- "active" for preferring active cooling
+
+		- "passive" for preferring passive cooling
+
+		The exact characteristics of both cooling modes depend
+		on the underlying ACPI firmware implementation.
diff --git a/MAINTAINERS b/MAINTAINERS
index 96b827049501..fd3102723518 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -382,6 +382,7 @@ R:	Zhang Rui <rui.zhang@...el.com>
 L:	linux-acpi@...r.kernel.org
 S:	Supported
 B:	https://bugzilla.kernel.org
+F:	Documentation/ABI/testing/sysfs-driver-thermal
 F:	drivers/acpi/*thermal*

 ACPI VIOT DRIVER
diff --git a/drivers/acpi/thermal.c b/drivers/acpi/thermal.c
index 5c2defe55898..52d0c777a93a 100644
--- a/drivers/acpi/thermal.c
+++ b/drivers/acpi/thermal.c
@@ -15,11 +15,14 @@

 #define pr_fmt(fmt) "ACPI: thermal: " fmt

+#include <linux/cleanup.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/dmi.h>
 #include <linux/init.h>
 #include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
 #include <linux/types.h>
 #include <linux/jiffies.h>
 #include <linux/kmod.h>
@@ -40,7 +43,6 @@
 #define ACPI_THERMAL_NOTIFY_DEVICES	0x82
 #define ACPI_THERMAL_NOTIFY_CRITICAL	0xF0
 #define ACPI_THERMAL_NOTIFY_HOT		0xF1
-#define ACPI_THERMAL_MODE_ACTIVE	0x00

 #define ACPI_THERMAL_MAX_ACTIVE		10
 #define ACPI_THERMAL_MAX_LIMIT_STR_LEN	65
@@ -85,6 +87,16 @@ MODULE_PARM_DESC(psv, "Disable or override all passive trip points.");

 static struct workqueue_struct *acpi_thermal_pm_queue;

+enum acpi_thermal_cooling_mode {
+	ACPI_THERMAL_MODE_ACTIVE	= 0x00,
+	ACPI_THERMAL_MODE_PASSIVE	= 0x01,
+};
+
+static const char * const acpi_thermal_cooling_mode_strings[] = {
+	[ACPI_THERMAL_MODE_ACTIVE]	= "active",
+	[ACPI_THERMAL_MODE_PASSIVE]	= "passive",
+};
+
 struct acpi_thermal_trip {
 	unsigned long temp_dk;
 	struct acpi_handle_list devices;
@@ -119,6 +131,9 @@ struct acpi_thermal {
 	struct work_struct thermal_check_work;
 	struct mutex thermal_check_lock;
 	refcount_t thermal_check_count;
+	bool supports_cooling_mode;
+	struct mutex cooling_mode_lock;       /* Protects cooling mode updates */
+	enum acpi_thermal_cooling_mode cooling_mode;
 };

 /* --------------------------------------------------------------------------
@@ -328,7 +343,6 @@ static void acpi_queue_thermal_check(struct acpi_thermal *tz)
 static void acpi_thermal_trips_update(struct acpi_thermal *tz, u32 event)
 {
 	struct adjust_trip_data atd = { .tz = tz, .event = event };
-	struct acpi_device *adev = tz->device;

 	/*
 	 * Use thermal_zone_for_each_trip() to carry out the trip points
@@ -340,8 +354,6 @@ static void acpi_thermal_trips_update(struct acpi_thermal *tz, u32 event)
 	thermal_zone_for_each_trip(tz->thermal_zone,
 				   acpi_thermal_adjust_trip, &atd);
 	acpi_queue_thermal_check(tz);
-	acpi_bus_generate_netlink_event(adev->pnp.device_class,
-					dev_name(&adev->dev), event, 0);
 }

 static int acpi_thermal_get_critical_trip(struct acpi_thermal *tz)
@@ -473,6 +485,18 @@ static void acpi_thermal_get_trip_points(struct acpi_thermal *tz)
 		tz->trips.active[i].trip.temp_dk = THERMAL_TEMP_INVALID;
 }

+static int acpi_thermal_set_cooling_mode(struct acpi_thermal *tz,
+					 enum acpi_thermal_cooling_mode mode)
+{
+	acpi_status status;
+
+	status = acpi_execute_simple_method(tz->device->handle, "_SCP", mode);
+	if (ACPI_FAILURE(status))
+		return -EIO;
+
+	return 0;
+}
+
 /* sys I/F for generic thermal sysfs support */

 static int thermal_get_temp(struct thermal_zone_device *thermal, int *temp)
@@ -683,6 +707,8 @@ static void acpi_thermal_notify(acpi_handle handle, u32 event, void *data)
 	case ACPI_THERMAL_NOTIFY_THRESHOLDS:
 	case ACPI_THERMAL_NOTIFY_DEVICES:
 		acpi_thermal_trips_update(tz, event);
+		acpi_bus_generate_netlink_event(device->pnp.device_class, dev_name(&device->dev),
+						event, 0);
 		break;
 	default:
 		acpi_handle_debug(device->handle, "Unsupported event [0x%x]\n",
@@ -777,6 +803,65 @@ static void acpi_thermal_free_thermal_zone(struct acpi_thermal *tz)
 	kfree(tz);
 }

+static ssize_t cooling_mode_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct acpi_thermal *tz = acpi_driver_data(to_acpi_device(dev));
+
+	guard(mutex)(&tz->cooling_mode_lock);
+
+	return sysfs_emit(buf, "%s\n", acpi_thermal_cooling_mode_strings[tz->cooling_mode]);
+}
+
+static ssize_t cooling_mode_store(struct device *dev, struct device_attribute *attr,
+				  const char *buf, size_t count)
+{
+	struct acpi_thermal *tz = acpi_driver_data(to_acpi_device(dev));
+	int ret, mode;
+
+	mode = sysfs_match_string(acpi_thermal_cooling_mode_strings, buf);
+	if (mode < 0)
+		return mode;
+
+	guard(mutex)(&tz->cooling_mode_lock);
+
+	ret = acpi_thermal_set_cooling_mode(tz, mode);
+	if (ret < 0)
+		return ret;
+
+	tz->cooling_mode = mode;
+	acpi_thermal_trips_update(tz, ACPI_THERMAL_NOTIFY_THRESHOLDS);
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(cooling_mode);
+
+static struct attribute *acpi_thermal_attrs[] = {
+	&dev_attr_cooling_mode.attr,
+	NULL
+};
+
+static umode_t acpi_thermal_group_is_visible(struct kobject *kobj, struct attribute *attr, int idx)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct acpi_thermal *tz = acpi_driver_data(to_acpi_device(dev));
+
+	if (tz->supports_cooling_mode)
+		return attr->mode;
+
+	return 0;
+}
+
+static const struct attribute_group acpi_thermal_group = {
+	.is_visible = acpi_thermal_group_is_visible,
+	.attrs = acpi_thermal_attrs,
+};
+
+static const struct attribute_group *acpi_thermal_groups[] = {
+	&acpi_thermal_group,
+	NULL
+};
+
 static int acpi_thermal_add(struct acpi_device *device)
 {
 	struct thermal_trip trip_table[ACPI_THERMAL_MAX_NR_TRIPS] = { 0 };
@@ -786,7 +871,7 @@ static int acpi_thermal_add(struct acpi_device *device)
 	int crit_temp, hot_temp;
 	int passive_delay = 0;
 	int result;
-	int i;
+	int ret, i;

 	if (!device)
 		return -EINVAL;
@@ -795,6 +880,10 @@ static int acpi_thermal_add(struct acpi_device *device)
 	if (!tz)
 		return -ENOMEM;

+	ret = devm_mutex_init(&device->dev, &tz->cooling_mode_lock);
+	if (ret < 0)
+		return ret;
+
 	tz->device = device;
 	strscpy(tz->name, device->pnp.bus_id);
 	strscpy(acpi_device_name(device), ACPI_THERMAL_DEVICE_NAME);
@@ -803,11 +892,18 @@ static int acpi_thermal_add(struct acpi_device *device)

 	acpi_thermal_aml_dependency_fix(tz);

-	/*
-	 * Set the cooling mode [_SCP] to active cooling. This needs to happen before
-	 * we retrieve the trip point values.
-	 */
-	acpi_execute_simple_method(tz->device->handle, "_SCP", ACPI_THERMAL_MODE_ACTIVE);
+	tz->supports_cooling_mode = acpi_has_method(tz->device->handle, "_SCP");
+	if (tz->supports_cooling_mode) {
+		/*
+		 * Set the initial cooling mode to active cooling. This needs to happen
+		 * before we retrieve the trip point values.
+		 */
+		ret = acpi_thermal_set_cooling_mode(tz, ACPI_THERMAL_MODE_ACTIVE);
+		if (ret < 0)
+			dev_err(&tz->device->dev, "Failed to set initial cooling mode\n");
+
+		tz->cooling_mode = ACPI_THERMAL_MODE_ACTIVE;
+	}

 	/* Get trip points [_ACi, _PSV, etc.] (required). */
 	acpi_thermal_get_trip_points(tz);
@@ -924,7 +1020,7 @@ static int acpi_thermal_suspend(struct device *dev)
 static int acpi_thermal_resume(struct device *dev)
 {
 	struct acpi_thermal *tz;
-	int i, j, power_state;
+	int ret, i, j, power_state;

 	if (!dev)
 		return -EINVAL;
@@ -933,6 +1029,12 @@ static int acpi_thermal_resume(struct device *dev)
 	if (!tz)
 		return -EINVAL;

+	if (tz->supports_cooling_mode) {
+		ret = acpi_thermal_set_cooling_mode(tz, tz->cooling_mode);
+		if (ret < 0)
+			dev_err(&tz->device->dev, "Failed to restore cooling mode\n");
+	}
+
 	for (i = 0; i < ACPI_THERMAL_MAX_ACTIVE; i++) {
 		struct acpi_thermal_trip *acpi_trip = &tz->trips.active[i].trip;

@@ -969,7 +1071,10 @@ static struct acpi_driver acpi_thermal_driver = {
 		.add = acpi_thermal_add,
 		.remove = acpi_thermal_remove,
 		},
-	.drv.pm = &acpi_thermal_pm,
+	.drv = {
+		.dev_groups = acpi_thermal_groups,
+		.pm = &acpi_thermal_pm,
+	},
 };

 static int thermal_act(const struct dmi_system_id *d)
--
2.39.5

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