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hwmon: Add thermal sensor driver for Surface Aggregator Module
Some of the newer Microsoft Surface devices (such as the Surface Book 3 and Pro 9) have thermal sensors connected via the Surface Aggregator Module (the embedded controller on those devices). Add a basic driver to read out the temperature values of those sensors. The EC can have up to 16 thermal sensors connected via a single sub-device, each providing temperature readings and a label string. Link: linux-surface/surface-aggregator-module#59 Reviewed-by: Hans de Goede <hdegoede@redhat.com> Co-developed-by: Ivor Wanders <ivor@iwanders.net> Signed-off-by: Ivor Wanders <ivor@iwanders.net> Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com> Message-ID: <20240811001503.753728-1-luzmaximilian@gmail.com> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
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‎MAINTAINERS‎

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F: Documentation/hwmon/surface_fan.rst
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F: drivers/hwmon/surface_fan.c
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MICROSOFT SURFACE SENSOR THERMAL DRIVER
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M: Maximilian Luz <luzmaximilian@gmail.com>
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L: linux-hwmon@vger.kernel.org
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S: Maintained
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F: drivers/hwmon/surface_temp.c
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MICROSOFT SURFACE GPE LID SUPPORT DRIVER
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M: Maximilian Luz <luzmaximilian@gmail.com>
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L: platform-driver-x86@vger.kernel.org

‎drivers/hwmon/Kconfig‎

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@@ -2082,6 +2082,17 @@ config SENSORS_SURFACE_FAN
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Select M or Y here, if you want to be able to read the fan's speed.
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config SENSORS_SURFACE_TEMP
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tristate "Microsoft Surface Thermal Sensor Driver"
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depends on SURFACE_AGGREGATOR
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depends on SURFACE_AGGREGATOR_BUS
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help
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Driver for monitoring thermal sensors connected via the Surface
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Aggregator Module (embedded controller) on Microsoft Surface devices.
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This driver can also be built as a module. If so, the module
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will be called surface_temp.
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config SENSORS_ADC128D818
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tristate "Texas Instruments ADC128D818"
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depends on I2C

‎drivers/hwmon/Makefile‎

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@@ -209,6 +209,7 @@ obj-$(CONFIG_SENSORS_SPARX5) += sparx5-temp.o
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obj-$(CONFIG_SENSORS_SPD5118) += spd5118.o
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obj-$(CONFIG_SENSORS_STTS751) += stts751.o
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obj-$(CONFIG_SENSORS_SURFACE_FAN)+= surface_fan.o
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obj-$(CONFIG_SENSORS_SURFACE_TEMP)+= surface_temp.o
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obj-$(CONFIG_SENSORS_SY7636A) += sy7636a-hwmon.o
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obj-$(CONFIG_SENSORS_AMC6821) += amc6821.o
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obj-$(CONFIG_SENSORS_TC74) += tc74.o

‎drivers/hwmon/surface_temp.c‎

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// SPDX-License-Identifier: GPL-2.0+
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/*
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* Thermal sensor subsystem driver for Surface System Aggregator Module (SSAM).
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*
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* Copyright (C) 2022-2023 Maximilian Luz <luzmaximilian@gmail.com>
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*/
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#include <linux/bitops.h>
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#include <linux/hwmon.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/types.h>
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#include <linux/surface_aggregator/controller.h>
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#include <linux/surface_aggregator/device.h>
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/* -- SAM interface. -------------------------------------------------------- */
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/*
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* Available sensors are indicated by a 16-bit bitfield, where a 1 marks the
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* presence of a sensor. So we have at most 16 possible sensors/channels.
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*/
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#define SSAM_TMP_SENSOR_MAX_COUNT 16
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/*
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* All names observed so far are 6 characters long, but there's only
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* zeros after the name, so perhaps they can be longer. This number reflects
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* the maximum zero-padded space observed in the returned buffer.
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*/
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#define SSAM_TMP_SENSOR_NAME_LENGTH 18
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struct ssam_tmp_get_name_rsp {
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__le16 unknown1;
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char unknown2;
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char name[SSAM_TMP_SENSOR_NAME_LENGTH];
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} __packed;
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static_assert(sizeof(struct ssam_tmp_get_name_rsp) == 21);
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SSAM_DEFINE_SYNC_REQUEST_CL_R(__ssam_tmp_get_available_sensors, __le16, {
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.target_category = SSAM_SSH_TC_TMP,
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.command_id = 0x04,
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});
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SSAM_DEFINE_SYNC_REQUEST_MD_R(__ssam_tmp_get_temperature, __le16, {
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.target_category = SSAM_SSH_TC_TMP,
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.command_id = 0x01,
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});
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SSAM_DEFINE_SYNC_REQUEST_MD_R(__ssam_tmp_get_name, struct ssam_tmp_get_name_rsp, {
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.target_category = SSAM_SSH_TC_TMP,
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.command_id = 0x0e,
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});
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static int ssam_tmp_get_available_sensors(struct ssam_device *sdev, s16 *sensors)
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{
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__le16 sensors_le;
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int status;
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status = __ssam_tmp_get_available_sensors(sdev, &sensors_le);
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if (status)
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return status;
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*sensors = le16_to_cpu(sensors_le);
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return 0;
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}
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static int ssam_tmp_get_temperature(struct ssam_device *sdev, u8 iid, long *temperature)
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{
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__le16 temp_le;
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int status;
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status = __ssam_tmp_get_temperature(sdev->ctrl, sdev->uid.target, iid, &temp_le);
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if (status)
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return status;
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/* Convert 1/10 °K to 1/1000 °C */
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*temperature = (le16_to_cpu(temp_le) - 2731) * 100L;
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return 0;
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}
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static int ssam_tmp_get_name(struct ssam_device *sdev, u8 iid, char *buf, size_t buf_len)
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{
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struct ssam_tmp_get_name_rsp name_rsp;
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int status;
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status = __ssam_tmp_get_name(sdev->ctrl, sdev->uid.target, iid, &name_rsp);
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if (status)
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return status;
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/*
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* This should not fail unless the name in the returned struct is not
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* null-terminated or someone changed something in the struct
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* definitions above, since our buffer and struct have the same
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* capacity by design. So if this fails, log an error message. Since
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* the more likely cause is that the returned string isn't
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* null-terminated, we might have received garbage (as opposed to just
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* an incomplete string), so also fail the function.
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*/
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status = strscpy(buf, name_rsp.name, buf_len);
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if (status < 0) {
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dev_err(&sdev->dev, "received non-null-terminated sensor name string\n");
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return status;
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}
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return 0;
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}
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/* -- Driver.---------------------------------------------------------------- */
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struct ssam_temp {
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struct ssam_device *sdev;
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s16 sensors;
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char names[SSAM_TMP_SENSOR_MAX_COUNT][SSAM_TMP_SENSOR_NAME_LENGTH];
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};
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static umode_t ssam_temp_hwmon_is_visible(const void *data,
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enum hwmon_sensor_types type,
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u32 attr, int channel)
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{
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const struct ssam_temp *ssam_temp = data;
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if (!(ssam_temp->sensors & BIT(channel)))
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return 0;
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return 0444;
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}
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static int ssam_temp_hwmon_read(struct device *dev,
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enum hwmon_sensor_types type,
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u32 attr, int channel, long *value)
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{
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const struct ssam_temp *ssam_temp = dev_get_drvdata(dev);
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return ssam_tmp_get_temperature(ssam_temp->sdev, channel + 1, value);
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}
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static int ssam_temp_hwmon_read_string(struct device *dev,
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enum hwmon_sensor_types type,
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u32 attr, int channel, const char **str)
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{
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const struct ssam_temp *ssam_temp = dev_get_drvdata(dev);
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*str = ssam_temp->names[channel];
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return 0;
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}
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static const struct hwmon_channel_info * const ssam_temp_hwmon_info[] = {
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HWMON_CHANNEL_INFO(chip,
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HWMON_C_REGISTER_TZ),
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HWMON_CHANNEL_INFO(temp,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL,
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HWMON_T_INPUT | HWMON_T_LABEL),
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NULL
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};
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static const struct hwmon_ops ssam_temp_hwmon_ops = {
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.is_visible = ssam_temp_hwmon_is_visible,
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.read = ssam_temp_hwmon_read,
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.read_string = ssam_temp_hwmon_read_string,
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};
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static const struct hwmon_chip_info ssam_temp_hwmon_chip_info = {
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.ops = &ssam_temp_hwmon_ops,
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.info = ssam_temp_hwmon_info,
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};
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static int ssam_temp_probe(struct ssam_device *sdev)
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{
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struct ssam_temp *ssam_temp;
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struct device *hwmon_dev;
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s16 sensors;
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int channel;
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int status;
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status = ssam_tmp_get_available_sensors(sdev, &sensors);
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if (status)
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return status;
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ssam_temp = devm_kzalloc(&sdev->dev, sizeof(*ssam_temp), GFP_KERNEL);
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if (!ssam_temp)
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return -ENOMEM;
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ssam_temp->sdev = sdev;
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ssam_temp->sensors = sensors;
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/* Retrieve the name for each available sensor. */
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for (channel = 0; channel < SSAM_TMP_SENSOR_MAX_COUNT; channel++) {
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if (!(sensors & BIT(channel)))
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continue;
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status = ssam_tmp_get_name(sdev, channel + 1, ssam_temp->names[channel],
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SSAM_TMP_SENSOR_NAME_LENGTH);
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if (status)
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return status;
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}
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hwmon_dev = devm_hwmon_device_register_with_info(&sdev->dev, "surface_thermal", ssam_temp,
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&ssam_temp_hwmon_chip_info, NULL);
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return PTR_ERR_OR_ZERO(hwmon_dev);
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}
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static const struct ssam_device_id ssam_temp_match[] = {
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{ SSAM_SDEV(TMP, SAM, 0x00, 0x02) },
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{ },
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};
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MODULE_DEVICE_TABLE(ssam, ssam_temp_match);
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static struct ssam_device_driver ssam_temp = {
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.probe = ssam_temp_probe,
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.match_table = ssam_temp_match,
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.driver = {
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.name = "surface_temp",
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.probe_type = PROBE_PREFER_ASYNCHRONOUS,
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},
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};
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module_ssam_device_driver(ssam_temp);
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MODULE_AUTHOR("Maximilian Luz <luzmaximilian@gmail.com>");
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MODULE_DESCRIPTION("Thermal sensor subsystem driver for Surface System Aggregator Module");
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MODULE_LICENSE("GPL");

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