hwmon: (ntc_thermistor) Add ntc thermistor to thermal subsystem as a sensor.

To get more comprehensive and integrated thermal management, it adds ntc
thermistor to thermal framework as a thermal sensor. It's governed thermal
susbsystem only if it is described in DT node. Otherwise, it just notifies
temperature to userspace via sysfs as it used to be.

Signed-off-by: Jonghwa Lee <jonghwa3.lee@samsung.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

2 files changed, 26 insertions, 0 deletions

diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 4289a4fa1a03..f790b41283d0 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1077,6 +1077,7 @@ config SENSORS_PC87427
 config SENSORS_NTC_THERMISTOR
         tristate "NTC thermistor support from Murata"
         depends on !OF || IIO=n || IIO
+        depends on THERMAL || !THERMAL_OF
         help
           This driver supports NTC thermistors sensor reading and its
           interpretation. The driver can also monitor the temperature and
diff --git a/drivers/hwmon/ntc_thermistor.c b/drivers/hwmon/ntc_thermistor.c
index bd410722cd4b..4ff89b2482e4 100644
--- a/drivers/hwmon/ntc_thermistor.c
+++ b/drivers/hwmon/ntc_thermistor.c
@@ -38,6 +38,7 @@
 
 #include <linux/hwmon.h>
 #include <linux/hwmon-sysfs.h>
+#include <linux/thermal.h>
 
 struct ntc_compensation {
         int             temp_c;
@@ -182,6 +183,7 @@ struct ntc_data {
         struct device *dev;
         int n_comp;
         char name[PLATFORM_NAME_SIZE];
+        struct thermal_zone_device *tz;
 };
 
 #if defined(CONFIG_OF) && IS_ENABLED(CONFIG_IIO)
@@ -428,6 +430,20 @@ static int ntc_thermistor_get_ohm(struct ntc_data *data)
         return -EINVAL;
 }
 
+static int ntc_read_temp(void *dev, long *temp)
+{
+        struct ntc_data *data = dev_get_drvdata(dev);
+        int ohm;
+
+        ohm = ntc_thermistor_get_ohm(data);
+        if (ohm < 0)
+                return ohm;
+
+        *temp = get_temp_mc(data, ohm);
+
+        return 0;
+}
+
 static ssize_t ntc_show_name(struct device *dev,
                 struct device_attribute *attr, char *buf)
 {
@@ -562,6 +578,13 @@ static int ntc_thermistor_probe(struct platform_device *pdev)
         dev_info(&pdev->dev, "Thermistor type: %s successfully probed.\n",
                                                                 pdev_id->name);
 
+        data->tz = thermal_zone_of_sensor_register(data->dev, 0, data->dev,
+                                                ntc_read_temp, NULL);
+        if (IS_ERR(data->tz)) {
+                dev_dbg(&pdev->dev, "Failed to register to thermal fw.\n");
+                data->tz = NULL;
+        }
+
         return 0;
 err_after_sysfs:
         sysfs_remove_group(&data->dev->kobj, &ntc_attr_group);
@@ -578,6 +601,8 @@ static int ntc_thermistor_remove(struct platform_device *pdev)
         sysfs_remove_group(&data->dev->kobj, &ntc_attr_group);
         ntc_iio_channel_release(pdata);
 
+        thermal_zone_of_sensor_unregister(data->dev, data->tz);
+
         return 0;
 }