ACPI: fan: Add fan speed reporting for fans with only _FST

Add support for ACPI fans with _FST to report their speed even if they do
not support fan control.

As suggested by Armin Wolf [1] and per the Windows Thermal Management
Design Guide [2], Samsung Galaxy Book series devices (and possibly many
more devices where the Windows guide was strictly followed) only implement
the _FST method and do not support ACPI-based fan control.

Currently, these fans are not supported by the kernel driver but this patch
will make some very small adjustments to allow them to be supported.

This patch is tested and working for me on a Samsung Galaxy Book2 Pro whose
DSDT (and several other Samsung Galaxy Book series notebooks which
currently have the same issue) can be found at [3].

Link: https://lore.kernel.org/platform-driver-x86/53c5075b-1967-45d0-937f-463912dd966d@gmx.de
Link: https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/design-guide
Link: https://github.com/joshuagrisham/samsung-galaxybook-extras/tree/8e3087a06b8bdcdfdd081367af4b744a56cc4ee9/dsdt
Signed-off-by: Joshua Grisham <josh@joshuagrisham.com>
Reviewed-by: Armin Wolf <W_Armin@gmx.de>
Link: https://patch.msgid.link/20250222094407.9753-1-josh@joshuagrisham.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/fan.h b/drivers/acpi/fan.h
index 488b51e2cb31db23e08efa68faaa3d8f9cd41da8..15eba1c70e66850fccb165ab9e34456a7203f835 100644 (file)
--- a/drivers/acpi/fan.h
+++ b/drivers/acpi/fan.h
@@ -49,6 +49,7 @@ struct acpi_fan_fst {
 
 struct acpi_fan {
        bool acpi4;
+       bool has_fst;
        struct acpi_fan_fif fif;
        struct acpi_fan_fps *fps;
        int fps_count;

diff --git a/drivers/acpi/fan_attr.c b/drivers/acpi/fan_attr.c
index f4f6e2381f1d3af4e3071d325da81dbf9d87ee01..22d29ac2447cc28d5c7bf30e02f4d7ce533f0017 100644 (file)
--- a/drivers/acpi/fan_attr.c
+++ b/drivers/acpi/fan_attr.c
@@ -75,15 +75,6 @@ int acpi_fan_create_attributes(struct acpi_device *device)
        struct acpi_fan *fan = acpi_driver_data(device);
        int i, status;
 
-       sysfs_attr_init(&fan->fine_grain_control.attr);
-       fan->fine_grain_control.show = show_fine_grain_control;
-       fan->fine_grain_control.store = NULL;
-       fan->fine_grain_control.attr.name = "fine_grain_control";
-       fan->fine_grain_control.attr.mode = 0444;
-       status = sysfs_create_file(&device->dev.kobj, &fan->fine_grain_control.attr);
-       if (status)
-               return status;
-
        /* _FST is present if we are here */
        sysfs_attr_init(&fan->fst_speed.attr);
        fan->fst_speed.show = show_fan_speed;
@@ -92,7 +83,19 @@ int acpi_fan_create_attributes(struct acpi_device *device)
        fan->fst_speed.attr.mode = 0444;
        status = sysfs_create_file(&device->dev.kobj, &fan->fst_speed.attr);
        if (status)
-               goto rem_fine_grain_attr;
+               return status;
+
+       if (!fan->acpi4)
+               return 0;
+
+       sysfs_attr_init(&fan->fine_grain_control.attr);
+       fan->fine_grain_control.show = show_fine_grain_control;
+       fan->fine_grain_control.store = NULL;
+       fan->fine_grain_control.attr.name = "fine_grain_control";
+       fan->fine_grain_control.attr.mode = 0444;
+       status = sysfs_create_file(&device->dev.kobj, &fan->fine_grain_control.attr);
+       if (status)
+               goto rem_fst_attr;
 
        for (i = 0; i < fan->fps_count; ++i) {
                struct acpi_fan_fps *fps = &fan->fps[i];
@@ -109,18 +112,18 @@ int acpi_fan_create_attributes(struct acpi_device *device)
 
                        for (j = 0; j < i; ++j)
                                sysfs_remove_file(&device->dev.kobj, &fan->fps[j].dev_attr.attr);
-                       goto rem_fst_attr;
+                       goto rem_fine_grain_attr;
                }
        }
 
        return 0;
 
-rem_fst_attr:
-       sysfs_remove_file(&device->dev.kobj, &fan->fst_speed.attr);
-
 rem_fine_grain_attr:
        sysfs_remove_file(&device->dev.kobj, &fan->fine_grain_control.attr);
 
+rem_fst_attr:
+       sysfs_remove_file(&device->dev.kobj, &fan->fst_speed.attr);
+
        return status;
 }
 
@@ -129,9 +132,13 @@ void acpi_fan_delete_attributes(struct acpi_device *device)
        struct acpi_fan *fan = acpi_driver_data(device);
        int i;
 
+       sysfs_remove_file(&device->dev.kobj, &fan->fst_speed.attr);
+
+       if (!fan->acpi4)
+               return;
+
        for (i = 0; i < fan->fps_count; ++i)
                sysfs_remove_file(&device->dev.kobj, &fan->fps[i].dev_attr.attr);
 
-       sysfs_remove_file(&device->dev.kobj, &fan->fst_speed.attr);
        sysfs_remove_file(&device->dev.kobj, &fan->fine_grain_control.attr);
 }

diff --git a/drivers/acpi/fan_core.c b/drivers/acpi/fan_core.c
index 10016f52f4f40eb2153a06bafe663bfdb89422a0..8ad12ad3aaaf4df1b28eb8eb15f4238965d4b0e2 100644 (file)
--- a/drivers/acpi/fan_core.c
+++ b/drivers/acpi/fan_core.c
@@ -203,12 +203,16 @@ static const struct thermal_cooling_device_ops fan_cooling_ops = {
  * --------------------------------------------------------------------------
 */
 
+static bool acpi_fan_has_fst(struct acpi_device *device)
+{
+       return acpi_has_method(device->handle, "_FST");
+}
+
 static bool acpi_fan_is_acpi4(struct acpi_device *device)
 {
        return acpi_has_method(device->handle, "_FIF") &&
               acpi_has_method(device->handle, "_FPS") &&
-              acpi_has_method(device->handle, "_FSL") &&
-              acpi_has_method(device->handle, "_FST");
+              acpi_has_method(device->handle, "_FSL");
 }
 
 static int acpi_fan_get_fif(struct acpi_device *device)
@@ -327,7 +331,12 @@ static int acpi_fan_probe(struct platform_device *pdev)
        device->driver_data = fan;
        platform_set_drvdata(pdev, fan);
 
-       if (acpi_fan_is_acpi4(device)) {
+       if (acpi_fan_has_fst(device)) {
+               fan->has_fst = true;
+               fan->acpi4 = acpi_fan_is_acpi4(device);
+       }
+
+       if (fan->acpi4) {
                result = acpi_fan_get_fif(device);
                if (result)
                        return result;
@@ -335,7 +344,9 @@ static int acpi_fan_probe(struct platform_device *pdev)
                result = acpi_fan_get_fps(device);
                if (result)
                        return result;
+       }
 
+       if (fan->has_fst) {
                result = devm_acpi_fan_create_hwmon(device);
                if (result)
                        return result;
@@ -343,9 +354,9 @@ static int acpi_fan_probe(struct platform_device *pdev)
                result = acpi_fan_create_attributes(device);
                if (result)
                        return result;
+       }
 
-               fan->acpi4 = true;
-       } else {
+       if (!fan->acpi4) {
                result = acpi_device_update_power(device, NULL);
                if (result) {
                        dev_err(&device->dev, "Failed to set initial power state\n");
@@ -391,7 +402,7 @@ err_remove_link:
 err_unregister:
        thermal_cooling_device_unregister(cdev);
 err_end:
-       if (fan->acpi4)
+       if (fan->has_fst)
                acpi_fan_delete_attributes(device);
 
        return result;
@@ -401,7 +412,7 @@ static void acpi_fan_remove(struct platform_device *pdev)
 {
        struct acpi_fan *fan = platform_get_drvdata(pdev);
 
-       if (fan->acpi4) {
+       if (fan->has_fst) {
                struct acpi_device *device = ACPI_COMPANION(&pdev->dev);
 
                acpi_fan_delete_attributes(device);

diff --git a/drivers/acpi/fan_hwmon.c b/drivers/acpi/fan_hwmon.c
index bd0d31a398fa59c926f8bc948d5ccfb10fbcf6df..e8d90605106efad4c10ae22c82a61c64224f8fa0 100644 (file)
--- a/drivers/acpi/fan_hwmon.c
+++ b/drivers/acpi/fan_hwmon.c
@@ -43,6 +43,10 @@ static umode_t acpi_fan_hwmon_is_visible(const void *drvdata, enum hwmon_sensor_
                case hwmon_fan_input:
                        return 0444;
                case hwmon_fan_target:
+                       /* Only acpi4 fans support fan control. */
+                       if (!fan->acpi4)
+                               return 0;
+
                        /*
                         * When in fine grain control mode, not every fan control value
                         * has an associated fan performance state.
@@ -57,6 +61,10 @@ static umode_t acpi_fan_hwmon_is_visible(const void *drvdata, enum hwmon_sensor_
        case hwmon_power:
                switch (attr) {
                case hwmon_power_input:
+                       /* Only acpi4 fans support fan control. */
+                       if (!fan->acpi4)
+                               return 0;
+
                        /*
                         * When in fine grain control mode, not every fan control value
                         * has an associated fan performance state.