hwmon: add fan speed monitoring driver for Surface devices

Adds a driver that provides read only access to the fan speed for Microsoft
Surface Pro devices. The fan speed is always regulated by the EC and cannot
be influenced directly.

Signed-off-by: Ivor Wanders <ivor@iwanders.net>
Link: https://github.com/linux-surface/kernel/pull/144
Reviewed-by: Maximilian Luz <luzmaximilian@gmail.com>
Reviewed-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20240131005856.10180-2-ivor@iwanders.net
[groeck:
 - Declare surface_fan_hwmon_is_visible() static
 - Add dependency on SURFACE_AGGREGATOR_BUS
]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index f16c6dfaec7dc9a4630cf98d698ed18be6e40e75..8f73badecba11cb39a53e28a137f71890bbaa779 100644 (file)
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -209,6 +209,7 @@ Hardware Monitoring Kernel Drivers
    smsc47m1
    sparx5-temp
    stpddc60
+   surface_fan
    sy7636a-hwmon
    tc654
    tc74

diff --git a/Documentation/hwmon/surface_fan.rst b/Documentation/hwmon/surface_fan.rst
new file mode 100644 (file)
index 0000000..0794257
--- /dev/null
+++ b/Documentation/hwmon/surface_fan.rst
@@ -0,0 +1,25 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver surface_fan
+=========================
+
+Supported Devices:
+
+  * Microsoft Surface Pro 9
+
+Author: Ivor Wanders <ivor@iwanders.net>
+
+Description
+-----------
+
+This provides monitoring of the fan found in some Microsoft Surface Pro devices,
+like the Surface Pro 9. The fan is always controlled by the onboard controller.
+
+Sysfs interface
+---------------
+
+======================= ======= =========================================
+Name                    Perm    Description
+======================= ======= =========================================
+``fan1_input``          RO      Current fan speed in RPM.
+======================= ======= =========================================

diff --git a/MAINTAINERS b/MAINTAINERS
index df8ea2d94a0cb77cc5072d130e93df7964197ae8..dd69696f3c0e83b91ffde6ee381ee952cdb7dd71 100644 (file)
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14549,6 +14549,14 @@ F:     Documentation/driver-api/surface_aggregator/clients/dtx.rst
 F:     drivers/platform/surface/surface_dtx.c
 F:     include/uapi/linux/surface_aggregator/dtx.h
 
+MICROSOFT SURFACE SENSOR FAN DRIVER
+M:     Maximilian Luz <luzmaximilian@gmail.com>
+M:     Ivor Wanders <ivor@iwanders.net>
+L:     linux-hwmon@vger.kernel.org
+S:     Maintained
+F:     Documentation/hwmon/surface_fan.rst
+F:     drivers/hwmon/surface_fan.c
+
 MICROSOFT SURFACE GPE LID SUPPORT DRIVER
 M:     Maximilian Luz <luzmaximilian@gmail.com>
 L:     platform-driver-x86@vger.kernel.org

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index f6160cc70077737ad00bede008283a80886f2218..cdf228fe50e2beb3fd1cd41030b1b2829c81447f 100644 (file)
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -2005,6 +2005,20 @@ config SENSORS_SFCTEMP
          This driver can also be built as a module.  If so, the module
          will be called sfctemp.
 
+config SENSORS_SURFACE_FAN
+       tristate "Surface Fan Driver"
+       depends on SURFACE_AGGREGATOR
+       depends on SURFACE_AGGREGATOR_BUS
+       help
+         Driver that provides monitoring of the fan on Surface Pro devices that
+         have a fan, like the Surface Pro 9.
+
+         This makes the fan's current speed accessible through the hwmon
+         system. It does not provide control over the fan, the firmware is
+         responsible for that, this driver merely provides monitoring.
+
+         Select M or Y here, if you want to be able to read the fan's speed.
+
 config SENSORS_ADC128D818
        tristate "Texas Instruments ADC128D818"
        depends on I2C

diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 8bfc422a29e532de8ac04bdac61e5e83398507b6..a49704cd48a4b522e617cbd8be9b6bd8ba70ff22 100644 (file)
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -202,6 +202,7 @@ obj-$(CONFIG_SENSORS_SMSC47M1)      += smsc47m1.o
 obj-$(CONFIG_SENSORS_SMSC47M192)+= smsc47m192.o
 obj-$(CONFIG_SENSORS_SPARX5)   += sparx5-temp.o
 obj-$(CONFIG_SENSORS_STTS751)  += stts751.o
+obj-$(CONFIG_SENSORS_SURFACE_FAN)+= surface_fan.o
 obj-$(CONFIG_SENSORS_SY7636A)  += sy7636a-hwmon.o
 obj-$(CONFIG_SENSORS_AMC6821)  += amc6821.o
 obj-$(CONFIG_SENSORS_TC74)     += tc74.o

diff --git a/drivers/hwmon/surface_fan.c b/drivers/hwmon/surface_fan.c
new file mode 100644 (file)
index 0000000..de3c5a2
--- /dev/null
+++ b/drivers/hwmon/surface_fan.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Surface Fan driver for Surface System Aggregator Module. It provides access
+ * to the fan's rpm through the hwmon system.
+ *
+ * Copyright (C) 2023 Ivor Wanders <ivor@iwanders.net>
+ */
+
+#include <linux/hwmon.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/surface_aggregator/device.h>
+#include <linux/types.h>
+
+// SSAM
+SSAM_DEFINE_SYNC_REQUEST_CL_R(__ssam_fan_rpm_get, __le16, {
+       .target_category = SSAM_SSH_TC_FAN,
+       .command_id      = 0x01,
+});
+
+// hwmon
+static umode_t surface_fan_hwmon_is_visible(const void *drvdata,
+                                           enum hwmon_sensor_types type, u32 attr,
+                                           int channel)
+{
+       return 0444;
+}
+
+static int surface_fan_hwmon_read(struct device *dev,
+                                 enum hwmon_sensor_types type, u32 attr,
+                                 int channel, long *val)
+{
+       struct ssam_device *sdev = dev_get_drvdata(dev);
+       int ret;
+       __le16 value;
+
+       ret = __ssam_fan_rpm_get(sdev, &value);
+       if (ret)
+               return ret;
+
+       *val = le16_to_cpu(value);
+
+       return 0;
+}
+
+static const struct hwmon_channel_info *const surface_fan_info[] = {
+       HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT),
+       NULL
+};
+
+static const struct hwmon_ops surface_fan_hwmon_ops = {
+       .is_visible = surface_fan_hwmon_is_visible,
+       .read = surface_fan_hwmon_read,
+};
+
+static const struct hwmon_chip_info surface_fan_chip_info = {
+       .ops = &surface_fan_hwmon_ops,
+       .info = surface_fan_info,
+};
+
+static int surface_fan_probe(struct ssam_device *sdev)
+{
+       struct device *hdev;
+
+       hdev = devm_hwmon_device_register_with_info(&sdev->dev,
+                                                   "surface_fan", sdev,
+                                                   &surface_fan_chip_info,
+                                                   NULL);
+
+       return PTR_ERR_OR_ZERO(hdev);
+}
+
+static const struct ssam_device_id ssam_fan_match[] = {
+       { SSAM_SDEV(FAN, SAM, 0x01, 0x01) },
+       {},
+};
+MODULE_DEVICE_TABLE(ssam, ssam_fan_match);
+
+static struct ssam_device_driver surface_fan = {
+       .probe = surface_fan_probe,
+       .match_table = ssam_fan_match,
+       .driver = {
+               .name = "surface_fan",
+               .probe_type = PROBE_PREFER_ASYNCHRONOUS,
+       },
+};
+module_ssam_device_driver(surface_fan);
+
+MODULE_AUTHOR("Ivor Wanders <ivor@iwanders.net>");
+MODULE_DESCRIPTION("Fan Driver for Surface System Aggregator Module");
+MODULE_LICENSE("GPL");