hwmon: add support for sensors exported via ARM SCMI

Create a driver to add support for SoC sensors exported by the System
Control Processor (SCP) via the System Control and Management Interface
(SCMI). The supported sensor types is one of voltage, temperature,
current, and power.

The sensor labels and values provided by the SCP are exported via the
hwmon sysfs interface.

Cc: linux-hwmon@vger.kernel.org
Acked-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/hwmon/Kconfig

@@ -317,6 +317,18 @@ config SENSORS_APPLESMC
 	  Say Y here if you have an applicable laptop and want to experience
 	  the awesome power of applesmc.
 
+config SENSORS_ARM_SCMI
+	tristate "ARM SCMI Sensors"
+	depends on ARM_SCMI_PROTOCOL
+	depends on THERMAL || !THERMAL_OF
+	help
+	  This driver provides support for temperature, voltage, current
+	  and power sensors available on SCMI based platforms. The actual
+	  number and type of sensors exported depend on the platform.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called scmi-hwmon.
+
 config SENSORS_ARM_SCPI
 	tristate "ARM SCPI Sensors"
 	depends on ARM_SCPI_PROTOCOL

drivers/hwmon/Makefile

@@ -46,6 +46,7 @@ obj-$(CONFIG_SENSORS_ADT7462)	+= adt7462.o
 obj-$(CONFIG_SENSORS_ADT7470)	+= adt7470.o
 obj-$(CONFIG_SENSORS_ADT7475)	+= adt7475.o
 obj-$(CONFIG_SENSORS_APPLESMC)	+= applesmc.o
+obj-$(CONFIG_SENSORS_ARM_SCMI)	+= scmi-hwmon.o
 obj-$(CONFIG_SENSORS_ARM_SCPI)	+= scpi-hwmon.o
 obj-$(CONFIG_SENSORS_ASC7621)	+= asc7621.o
 obj-$(CONFIG_SENSORS_ASPEED)	+= aspeed-pwm-tacho.o

drivers/hwmon/scmi-hwmon.c

@@ -0,0 +1,225 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * System Control and Management Interface(SCMI) based hwmon sensor driver
+ *
+ * Copyright (C) 2018 ARM Ltd.
+ * Sudeep Holla <sudeep.holla@arm.com>
+ */
+
+#include <linux/hwmon.h>
+#include <linux/module.h>
+#include <linux/scmi_protocol.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/thermal.h>
+
+struct scmi_sensors {
+	const struct scmi_handle *handle;
+	const struct scmi_sensor_info **info[hwmon_max];
+};
+
+static int scmi_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
+			   u32 attr, int channel, long *val)
+{
+	int ret;
+	u64 value;
+	const struct scmi_sensor_info *sensor;
+	struct scmi_sensors *scmi_sensors = dev_get_drvdata(dev);
+	const struct scmi_handle *h = scmi_sensors->handle;
+
+	sensor = *(scmi_sensors->info[type] + channel);
+	ret = h->sensor_ops->reading_get(h, sensor->id, false, &value);
+	if (!ret)
+		*val = value;
+
+	return ret;
+}
+
+static int
+scmi_hwmon_read_string(struct device *dev, enum hwmon_sensor_types type,
+		       u32 attr, int channel, const char **str)
+{
+	const struct scmi_sensor_info *sensor;
+	struct scmi_sensors *scmi_sensors = dev_get_drvdata(dev);
+
+	sensor = *(scmi_sensors->info[type] + channel);
+	*str = sensor->name;
+
+	return 0;
+}
+
+static umode_t
+scmi_hwmon_is_visible(const void *drvdata, enum hwmon_sensor_types type,
+		      u32 attr, int channel)
+{
+	const struct scmi_sensor_info *sensor;
+	const struct scmi_sensors *scmi_sensors = drvdata;
+
+	sensor = *(scmi_sensors->info[type] + channel);
+	if (sensor && sensor->name)
+		return S_IRUGO;
+
+	return 0;
+}
+
+static const struct hwmon_ops scmi_hwmon_ops = {
+	.is_visible = scmi_hwmon_is_visible,
+	.read = scmi_hwmon_read,
+	.read_string = scmi_hwmon_read_string,
+};
+
+static struct hwmon_chip_info scmi_chip_info = {
+	.ops = &scmi_hwmon_ops,
+	.info = NULL,
+};
+
+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)
+{
+	int i;
+	u32 *cfg = devm_kcalloc(dev, num + 1, sizeof(*cfg), GFP_KERNEL);
+
+	if (!cfg)
+		return -ENOMEM;
+
+	scmi_hwmon_chan->type = type;
+	scmi_hwmon_chan->config = cfg;
+	for (i = 0; i < num; i++, cfg++)
+		*cfg = config;
+
+	return 0;
+}
+
+static enum hwmon_sensor_types scmi_types[] = {
+	[TEMPERATURE_C] = hwmon_temp,
+	[VOLTAGE] = hwmon_in,
+	[CURRENT] = hwmon_curr,
+	[POWER] = hwmon_power,
+	[ENERGY] = hwmon_energy,
+};
+
+static u32 hwmon_attributes[] = {
+	[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,
+	[hwmon_power] = HWMON_P_INPUT | HWMON_P_LABEL,
+	[hwmon_energy] = HWMON_E_INPUT | HWMON_E_LABEL,
+};
+
+static int scmi_hwmon_probe(struct scmi_device *sdev)
+{
+	int i, idx;
+	u16 nr_sensors;
+	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;
+	const struct hwmon_chip_info *chip_info;
+	struct device *hwdev, *dev = &sdev->dev;
+	struct hwmon_channel_info *scmi_hwmon_chan;
+	const struct hwmon_channel_info **ptr_scmi_ci;
+	const struct scmi_handle *handle = sdev->handle;
+
+	if (!handle || !handle->sensor_ops)
+		return -ENODEV;
+
+	nr_sensors = handle->sensor_ops->count_get(handle);
+	if (!nr_sensors)
+		return -EIO;
+
+	scmi_sensors = devm_kzalloc(dev, sizeof(*scmi_sensors), GFP_KERNEL);
+	if (!scmi_sensors)
+		return -ENOMEM;
+
+	scmi_sensors->handle = handle;
+
+	for (i = 0; i < nr_sensors; i++) {
+		sensor = handle->sensor_ops->info_get(handle, i);
+		if (!sensor)
+			return PTR_ERR(sensor);
+
+		switch (sensor->type) {
+		case TEMPERATURE_C:
+		case VOLTAGE:
+		case CURRENT:
+		case POWER:
+		case ENERGY:
+			type = scmi_types[sensor->type];
+			if (!nr_count[type])
+				nr_types++;
+			nr_count[type]++;
+			break;
+		}
+	}
+
+	if (nr_count[hwmon_temp])
+		nr_count[hwmon_chip]++, nr_types++;
+
+	scmi_hwmon_chan = devm_kcalloc(dev, nr_types, sizeof(*scmi_hwmon_chan),
+				       GFP_KERNEL);
+	if (!scmi_hwmon_chan)
+		return -ENOMEM;
+
+	ptr_scmi_ci = devm_kcalloc(dev, nr_types + 1, sizeof(*ptr_scmi_ci),
+				   GFP_KERNEL);
+	if (!ptr_scmi_ci)
+		return -ENOMEM;
+
+	scmi_chip_info.info = ptr_scmi_ci;
+	chip_info = &scmi_chip_info;
+
+	for (type = 0; type < hwmon_max && nr_count[type]; type++) {
+		scmi_hwmon_add_chan_info(scmi_hwmon_chan, dev, nr_count[type],
+					 type, hwmon_attributes[type]);
+		*ptr_scmi_ci++ = scmi_hwmon_chan++;
+
+		scmi_sensors->info[type] =
+			devm_kcalloc(dev, nr_count[type],
+				     sizeof(*scmi_sensors->info), GFP_KERNEL);
+		if (!scmi_sensors->info[type])
+			return -ENOMEM;
+	}
+
+	for (i = nr_sensors - 1; i >= 0 ; i--) {
+		sensor = handle->sensor_ops->info_get(handle, i);
+		if (!sensor)
+			continue;
+
+		switch (sensor->type) {
+		case TEMPERATURE_C:
+		case VOLTAGE:
+		case CURRENT:
+		case POWER:
+		case ENERGY:
+			type = scmi_types[sensor->type];
+			idx = --nr_count[type];
+			*(scmi_sensors->info[type] + idx) = sensor;
+			break;
+		}
+	}
+
+	hwdev = devm_hwmon_device_register_with_info(dev, "scmi_sensors",
+						     scmi_sensors, chip_info,
+						     NULL);
+
+	return PTR_ERR_OR_ZERO(hwdev);
+}
+
+static const struct scmi_device_id scmi_id_table[] = {
+	{ SCMI_PROTOCOL_SENSOR },
+	{ },
+};
+MODULE_DEVICE_TABLE(scmi, scmi_id_table);
+
+static struct scmi_driver scmi_hwmon_drv = {
+	.name		= "scmi-hwmon",
+	.probe		= scmi_hwmon_probe,
+	.id_table	= scmi_id_table,
+};
+module_scmi_driver(scmi_hwmon_drv);
+
+MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
+MODULE_DESCRIPTION("ARM SCMI HWMON interface driver");
+MODULE_LICENSE("GPL v2");