1 files changed, 245 insertions, 14 deletions

diff --git a/drivers/acpi/fan_core.c b/drivers/acpi/fan_core.c
index 04ff608f2ff0..fb08b8549ed7 100644
--- a/drivers/acpi/fan_core.c
+++ b/drivers/acpi/fan_core.c
@@ -7,11 +7,16 @@
  *  Copyright (C) 2022 Intel Corporation. All rights reserved.
  */
 
+#include <linux/bits.h>
 #include <linux/kernel.h>
+#include <linux/limits.h>
+#include <linux/math.h>
+#include <linux/math64.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/types.h>
 #include <linux/uaccess.h>
+#include <linux/uuid.h>
 #include <linux/thermal.h>
 #include <linux/acpi.h>
 #include <linux/platform_device.h>
@@ -19,6 +24,26 @@
 
 #include "fan.h"
 
+#define ACPI_FAN_NOTIFY_STATE_CHANGED	0x80
+
+/*
+ * Defined inside the "Fan Noise Signal" section at
+ * https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/design-guide.
+ */
+static const guid_t acpi_fan_microsoft_guid = GUID_INIT(0xA7611840, 0x99FE, 0x41AE, 0xA4, 0x88,
+							0x35, 0xC7, 0x59, 0x26, 0xC8, 0xEB);
+#define ACPI_FAN_DSM_GET_TRIP_POINT_GRANULARITY 1
+#define ACPI_FAN_DSM_SET_TRIP_POINTS		2
+#define ACPI_FAN_DSM_GET_OPERATING_RANGES	3
+
+/*
+ * Ensures that fans with a very low trip point granularity
+ * do not send too many notifications.
+ */
+static uint min_trip_distance = 100;
+module_param(min_trip_distance, uint, 0);
+MODULE_PARM_DESC(min_trip_distance, "Minimum distance between fan speed trip points in RPM");
+
 static const struct acpi_device_id fan_device_ids[] = {
 	ACPI_FAN_DEVICE_IDS,
 	{"", 0},
@@ -44,25 +69,30 @@ static int fan_get_max_state(struct thermal_cooling_device *cdev, unsigned long
 	return 0;
 }
 
-int acpi_fan_get_fst(struct acpi_device *device, struct acpi_fan_fst *fst)
+int acpi_fan_get_fst(acpi_handle handle, struct acpi_fan_fst *fst)
 {
 	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
 	union acpi_object *obj;
 	acpi_status status;
 	int ret = 0;
 
-	status = acpi_evaluate_object(device->handle, "_FST", NULL, &buffer);
-	if (ACPI_FAILURE(status)) {
-		dev_err(&device->dev, "Get fan state failed\n");
-		return -ENODEV;
-	}
+	status = acpi_evaluate_object(handle, "_FST", NULL, &buffer);
+	if (ACPI_FAILURE(status))
+		return -EIO;
 
 	obj = buffer.pointer;
-	if (!obj || obj->type != ACPI_TYPE_PACKAGE ||
-	    obj->package.count != 3 ||
-	    obj->package.elements[1].type != ACPI_TYPE_INTEGER) {
-		dev_err(&device->dev, "Invalid _FST data\n");
-		ret = -EINVAL;
+	if (!obj)
+		return -ENODATA;
+
+	if (obj->type != ACPI_TYPE_PACKAGE || obj->package.count != 3) {
+		ret = -EPROTO;
+		goto err;
+	}
+
+	if (obj->package.elements[0].type != ACPI_TYPE_INTEGER ||
+	    obj->package.elements[1].type != ACPI_TYPE_INTEGER ||
+	    obj->package.elements[2].type != ACPI_TYPE_INTEGER) {
+		ret = -EPROTO;
 		goto err;
 	}
 
@@ -81,7 +111,7 @@ static int fan_get_state_acpi4(struct acpi_device *device, unsigned long *state)
 	struct acpi_fan_fst fst;
 	int status, i;
 
-	status = acpi_fan_get_fst(device, &fst);
+	status = acpi_fan_get_fst(device->handle, &fst);
 	if (status)
 		return status;
 
@@ -303,6 +333,182 @@ err:
 	return status;
 }
 
+static int acpi_fan_dsm_init(struct device *dev)
+{
+	union acpi_object dummy = {
+		.package = {
+			.type = ACPI_TYPE_PACKAGE,
+			.count = 0,
+			.elements = NULL,
+		},
+	};
+	struct acpi_fan *fan = dev_get_drvdata(dev);
+	union acpi_object *obj;
+	int ret = 0;
+
+	if (!acpi_check_dsm(fan->handle, &acpi_fan_microsoft_guid, 0,
+			    BIT(ACPI_FAN_DSM_GET_TRIP_POINT_GRANULARITY) |
+			    BIT(ACPI_FAN_DSM_SET_TRIP_POINTS)))
+		return 0;
+
+	dev_info(dev, "Using Microsoft fan extensions\n");
+
+	obj = acpi_evaluate_dsm_typed(fan->handle, &acpi_fan_microsoft_guid, 0,
+				      ACPI_FAN_DSM_GET_TRIP_POINT_GRANULARITY, &dummy,
+				      ACPI_TYPE_INTEGER);
+	if (!obj)
+		return -EIO;
+
+	if (obj->integer.value > U32_MAX)
+		ret = -EOVERFLOW;
+	else
+		fan->fan_trip_granularity = obj->integer.value;
+
+	kfree(obj);
+
+	return ret;
+}
+
+static int acpi_fan_dsm_set_trip_points(struct device *dev, u64 upper, u64 lower)
+{
+	union acpi_object args[2] = {
+		{
+			.integer = {
+				.type = ACPI_TYPE_INTEGER,
+				.value = lower,
+			},
+		},
+		{
+			.integer = {
+				.type = ACPI_TYPE_INTEGER,
+				.value = upper,
+			},
+		},
+	};
+	struct acpi_fan *fan = dev_get_drvdata(dev);
+	union acpi_object in = {
+		.package = {
+			.type = ACPI_TYPE_PACKAGE,
+			.count = ARRAY_SIZE(args),
+			.elements = args,
+		},
+	};
+	union acpi_object *obj;
+
+	obj = acpi_evaluate_dsm(fan->handle, &acpi_fan_microsoft_guid, 0,
+				ACPI_FAN_DSM_SET_TRIP_POINTS, &in);
+	kfree(obj);
+
+	return 0;
+}
+
+static int acpi_fan_dsm_start(struct device *dev)
+{
+	struct acpi_fan *fan = dev_get_drvdata(dev);
+	int ret;
+
+	if (!fan->fan_trip_granularity)
+		return 0;
+
+	/*
+	 * Some firmware implementations only update the values returned by the
+	 * _FST control method when a notification is received. This usually
+	 * works with Microsoft Windows as setting up trip points will keep
+	 * triggering said notifications, but will cause issues when using _FST
+	 * without the Microsoft-specific trip point extension.
+	 *
+	 * Because of this, an initial notification needs to be triggered to
+	 * start the cycle of trip points updates. This is achieved by setting
+	 * the trip points sequencially to two separate ranges. As by the
+	 * Microsoft specification the firmware should trigger a notification
+	 * immediately if the fan speed is outside the trip point range. This
+	 * _should_ result in at least one notification as both ranges do not
+	 * overlap, meaning that the current fan speed needs to be outside at
+	 * least one range.
+	 */
+	ret = acpi_fan_dsm_set_trip_points(dev, fan->fan_trip_granularity, 0);
+	if (ret < 0)
+		return ret;
+
+	return acpi_fan_dsm_set_trip_points(dev, fan->fan_trip_granularity * 3,
+					    fan->fan_trip_granularity * 2);
+}
+
+static int acpi_fan_dsm_update_trips_points(struct device *dev, struct acpi_fan_fst *fst)
+{
+	struct acpi_fan *fan = dev_get_drvdata(dev);
+	u64 upper, lower;
+
+	if (!fan->fan_trip_granularity)
+		return 0;
+
+	if (!acpi_fan_speed_valid(fst->speed))
+		return -EINVAL;
+
+	upper = roundup_u64(fst->speed + min_trip_distance, fan->fan_trip_granularity);
+	if (fst->speed <= min_trip_distance) {
+		lower = 0;
+	} else {
+		/*
+		 * Valid fan speed values cannot be larger than 32 bit, so
+		 * we can safely assume that no overflow will happen here.
+		 */
+		lower = rounddown((u32)fst->speed - min_trip_distance, fan->fan_trip_granularity);
+	}
+
+	return acpi_fan_dsm_set_trip_points(dev, upper, lower);
+}
+
+static void acpi_fan_notify_handler(acpi_handle handle, u32 event, void *context)
+{
+	struct device *dev = context;
+	struct acpi_fan_fst fst;
+	int ret;
+
+	switch (event) {
+	case ACPI_FAN_NOTIFY_STATE_CHANGED:
+		/*
+		 * The ACPI specification says that we must evaluate _FST when we
+		 * receive an ACPI event indicating that the fan state has changed.
+		 */
+		ret = acpi_fan_get_fst(handle, &fst);
+		if (ret < 0) {
+			dev_err(dev, "Error retrieving current fan status: %d\n", ret);
+		} else {
+			ret = acpi_fan_dsm_update_trips_points(dev, &fst);
+			if (ret < 0)
+				dev_err(dev, "Failed to update trip points: %d\n", ret);
+		}
+
+		acpi_fan_notify_hwmon(dev);
+		acpi_bus_generate_netlink_event("fan", dev_name(dev), event, 0);
+		break;
+	default:
+		dev_dbg(dev, "Unsupported ACPI notification 0x%x\n", event);
+		break;
+	}
+}
+
+static void acpi_fan_notify_remove(void *data)
+{
+	struct acpi_fan *fan = data;
+
+	acpi_remove_notify_handler(fan->handle, ACPI_DEVICE_NOTIFY, acpi_fan_notify_handler);
+}
+
+static int devm_acpi_fan_notify_init(struct device *dev)
+{
+	struct acpi_fan *fan = dev_get_drvdata(dev);
+	acpi_status status;
+
+	status = acpi_install_notify_handler(fan->handle, ACPI_DEVICE_NOTIFY,
+					     acpi_fan_notify_handler, dev);
+	if (ACPI_FAILURE(status))
+		return -EIO;
+
+	return devm_add_action_or_reset(dev, acpi_fan_notify_remove, fan);
+}
+
 static int acpi_fan_probe(struct platform_device *pdev)
 {
 	int result = 0;
@@ -311,11 +517,16 @@ static int acpi_fan_probe(struct platform_device *pdev)
 	struct acpi_device *device = ACPI_COMPANION(&pdev->dev);
 	char *name;
 
+	if (!device)
+		return -ENODEV;
+
 	fan = devm_kzalloc(&pdev->dev, sizeof(*fan), GFP_KERNEL);
 	if (!fan) {
 		dev_err(&device->dev, "No memory for fan\n");
 		return -ENOMEM;
 	}
+
+	fan->handle = device->handle;
 	device->driver_data = fan;
 	platform_set_drvdata(pdev, fan);
 
@@ -337,10 +548,24 @@ static int acpi_fan_probe(struct platform_device *pdev)
 	}
 
 	if (fan->has_fst) {
-		result = devm_acpi_fan_create_hwmon(device);
+		result = acpi_fan_dsm_init(&pdev->dev);
+		if (result)
+			return result;
+
+		result = devm_acpi_fan_create_hwmon(&pdev->dev);
+		if (result)
+			return result;
+
+		result = devm_acpi_fan_notify_init(&pdev->dev);
 		if (result)
 			return result;
 
+		result = acpi_fan_dsm_start(&pdev->dev);
+		if (result) {
+			dev_err(&pdev->dev, "Failed to start Microsoft fan extensions\n");
+			return result;
+		}
+
 		result = acpi_fan_create_attributes(device);
 		if (result)
 			return result;
@@ -426,8 +651,14 @@ static int acpi_fan_suspend(struct device *dev)
 
 static int acpi_fan_resume(struct device *dev)
 {
-	int result;
 	struct acpi_fan *fan = dev_get_drvdata(dev);
+	int result;
+
+	if (fan->has_fst) {
+		result = acpi_fan_dsm_start(dev);
+		if (result)
+			dev_err(dev, "Failed to start Microsoft fan extensions: %d\n", result);
+	}
 
 	if (fan->acpi4)
 		return 0;