hwmon: (scmi) Register explicitly with Thermal Framework

Available sensors are enumerated and reported by the SCMI platform server
using a 16bit identification number; not all such sensors are of a type
supported by hwmon subsystem and, among the supported ones, only a subset
could be temperature sensors that have to be registered with the Thermal
Framework.
Potential clashes between hwmon channels indexes and the underlying real
sensors IDs do not play well with the hwmon<-->thermal bridge automatic
registration routines and could need a sensible number of fake dummy
sensors to be made up in order to keep indexes and IDs in sync.

Avoid to use the hwmon<-->thermal bridge dropping the HWMON_C_REGISTER_TZ
attribute and instead explicit register temperature sensors directly with
the Thermal Framework.

Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: linux-hwmon@vger.kernel.org
Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20221031114018.59048-1-cristian.marussi@arm.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/scmi-hwmon.c

@@ -20,6 +20,11 @@ struct scmi_sensors {
 	const struct scmi_sensor_info **info[hwmon_max];
 };
 
+struct scmi_thermal_sensor {
+	const struct scmi_protocol_handle *ph;
+	const struct scmi_sensor_info *info;
+};
+
 static inline u64 __pow10(u8 x)
 {
 	u64 r = 1;
@@ -64,16 +69,14 @@ static int scmi_hwmon_scale(const struct scmi_sensor_info *sensor, u64 *value)
 	return 0;
 }
 
-static int scmi_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
-			   u32 attr, int channel, long *val)
+static int scmi_hwmon_read_scaled_value(const struct scmi_protocol_handle *ph,
+					const struct scmi_sensor_info *sensor,
+					long *val)
 {
 	int ret;
 	u64 value;
-	const struct scmi_sensor_info *sensor;
-	struct scmi_sensors *scmi_sensors = dev_get_drvdata(dev);
 
-	sensor = *(scmi_sensors->info[type] + channel);
-	ret = sensor_ops->reading_get(scmi_sensors->ph, sensor->id, &value);
+	ret = sensor_ops->reading_get(ph, sensor->id, &value);
 	if (ret)
 		return ret;
 
@@ -84,6 +87,17 @@ static int scmi_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
 	return ret;
 }
 
+static int scmi_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
+			   u32 attr, int channel, long *val)
+{
+	const struct scmi_sensor_info *sensor;
+	struct scmi_sensors *scmi_sensors = dev_get_drvdata(dev);
+
+	sensor = *(scmi_sensors->info[type] + channel);
+
+	return scmi_hwmon_read_scaled_value(scmi_sensors->ph, sensor, val);
+}
+
 static int
 scmi_hwmon_read_string(struct device *dev, enum hwmon_sensor_types type,
 		       u32 attr, int channel, const char **str)
@@ -122,6 +136,25 @@ static struct hwmon_chip_info scmi_chip_info = {
 	.info = NULL,
 };
 
+static int scmi_hwmon_thermal_get_temp(struct thermal_zone_device *tz,
+				       int *temp)
+{
+	int ret;
+	long value;
+	struct scmi_thermal_sensor *th_sensor = tz->devdata;
+
+	ret = scmi_hwmon_read_scaled_value(th_sensor->ph, th_sensor->info,
+					   &value);
+	if (!ret)
+		*temp = value;
+
+	return ret;
+}
+
+static const struct thermal_zone_device_ops scmi_hwmon_thermal_ops = {
+	.get_temp = scmi_hwmon_thermal_get_temp,
+};
+
 static int scmi_hwmon_add_chan_info(struct hwmon_channel_info *scmi_hwmon_chan,
 				    struct device *dev, int num,
 				    enum hwmon_sensor_types type, u32 config)
@@ -149,7 +182,6 @@ static enum hwmon_sensor_types scmi_types[] = {
 };
 
 static u32 hwmon_attributes[hwmon_max] = {
-	[hwmon_chip] = HWMON_C_REGISTER_TZ,
 	[hwmon_temp] = HWMON_T_INPUT | HWMON_T_LABEL,
 	[hwmon_in] = HWMON_I_INPUT | HWMON_I_LABEL,
 	[hwmon_curr] = HWMON_C_INPUT | HWMON_C_LABEL,
@@ -157,6 +189,43 @@ static u32 hwmon_attributes[hwmon_max] = {
 	[hwmon_energy] = HWMON_E_INPUT | HWMON_E_LABEL,
 };
 
+static int scmi_thermal_sensor_register(struct device *dev,
+					const struct scmi_protocol_handle *ph,
+					const struct scmi_sensor_info *sensor)
+{
+	struct scmi_thermal_sensor *th_sensor;
+	struct thermal_zone_device *tzd;
+
+	th_sensor = devm_kzalloc(dev, sizeof(*th_sensor), GFP_KERNEL);
+	if (!th_sensor)
+		return -ENOMEM;
+
+	th_sensor->ph = ph;
+	th_sensor->info = sensor;
+
+	/*
+	 * Try to register a temperature sensor with the Thermal Framework:
+	 * skip sensors not defined as part of any thermal zone (-ENODEV) but
+	 * report any other errors related to misconfigured zones/sensors.
+	 */
+	tzd = devm_thermal_of_zone_register(dev, th_sensor->info->id, th_sensor,
+					    &scmi_hwmon_thermal_ops);
+	if (IS_ERR(tzd)) {
+		devm_kfree(dev, th_sensor);
+
+		if (PTR_ERR(tzd) != -ENODEV)
+			return PTR_ERR(tzd);
+
+		dev_dbg(dev, "Sensor '%s' not attached to any thermal zone.\n",
+			sensor->name);
+	} else {
+		dev_dbg(dev, "Sensor '%s' attached to thermal zone ID:%d\n",
+			sensor->name, tzd->id);
+	}
+
+	return 0;
+}
+
 static int scmi_hwmon_probe(struct scmi_device *sdev)
 {
 	int i, idx;
@@ -164,7 +233,7 @@ static int scmi_hwmon_probe(struct scmi_device *sdev)
 	enum hwmon_sensor_types type;
 	struct scmi_sensors *scmi_sensors;
 	const struct scmi_sensor_info *sensor;
-	int nr_count[hwmon_max] = {0}, nr_types = 0;
+	int nr_count[hwmon_max] = {0}, nr_types = 0, nr_count_temp = 0;
 	const struct hwmon_chip_info *chip_info;
 	struct device *hwdev, *dev = &sdev->dev;
 	struct hwmon_channel_info *scmi_hwmon_chan;
@@ -208,10 +277,8 @@ static int scmi_hwmon_probe(struct scmi_device *sdev)
 		}
 	}
 
-	if (nr_count[hwmon_temp]) {
-		nr_count[hwmon_chip]++;
-		nr_types++;
-	}
+	if (nr_count[hwmon_temp])
+		nr_count_temp = nr_count[hwmon_temp];
 
 	scmi_hwmon_chan = devm_kcalloc(dev, nr_types, sizeof(*scmi_hwmon_chan),
 				       GFP_KERNEL);
@@ -262,8 +329,31 @@ static int scmi_hwmon_probe(struct scmi_device *sdev)
 	hwdev = devm_hwmon_device_register_with_info(dev, "scmi_sensors",
 						     scmi_sensors, chip_info,
 						     NULL);
+	if (IS_ERR(hwdev))
+		return PTR_ERR(hwdev);
 
-	return PTR_ERR_OR_ZERO(hwdev);
+	for (i = 0; i < nr_count_temp; i++) {
+		int ret;
+
+		sensor = *(scmi_sensors->info[hwmon_temp] + i);
+		if (!sensor)
+			continue;
+
+		/*
+		 * Warn on any misconfiguration related to thermal zones but
+		 * bail out of probing only on memory errors.
+		 */
+		ret = scmi_thermal_sensor_register(dev, ph, sensor);
+		if (ret) {
+			if (ret == -ENOMEM)
+				return ret;
+			dev_warn(dev,
+				 "Thermal zone misconfigured for %s. err=%d\n",
+				 sensor->name, ret);
+		}
+	}
+
+	return 0;
 }
 
 static const struct scmi_device_id scmi_id_table[] = {