hwmon: (ntc_thermistor) Add DT with IIO support to NTC thermistor driver

This patch adds DT support to NTC driver to parse the
platform data.

Also adds the support to work as an iio device client.

During the probe ntc driver gets the respective channels of ADC
and uses iio_raw_read calls to get the ADC converted value.

Signed-off-by: Naveen Krishna Chatradhi <[e-mail]>
[Guenter Roeck: fixed Kconfig dependencies; use ERR_CAST]
Tested-by: Doug Anderson <[e-mail]>
Signed-off-by: Guenter Roeck <[e-mail]>

Documentation/devicetree/bindings/hwmon/ntc_thermistor.txt

···
+NTC Thermistor hwmon sensors
+-------------------------------
+
+Requires node properties:
+- "compatible" value : one of
+	"ntc,ncp15wb473"
+	"ntc,ncp18wb473"
+	"ntc,ncp21wb473"
+	"ntc,ncp03wb473"
+	"ntc,ncp15wl333"
+- "pullup-uv"	Pull up voltage in micro volts
+- "pullup-ohm"	Pull up resistor value in ohms
+- "pulldown-ohm" Pull down resistor value in ohms
+- "connected-positive" Always ON, If not specified.
+		Status change is possible.
+- "io-channels"	Channel node of ADC to be used for
+		conversion.
+
+Read more about iio bindings at
+	Documentation/devicetree/bindings/iio/iio-bindings.txt
+
+Example:
+	ncp15wb473@0 {
+		compatible = "ntc,ncp15wb473";
+		pullup-uv = <1800000>;
+		pullup-ohm = <47000>;
+		pulldown-ohm = <0>;
+		io-channels = <&adc 3>;
+	};

drivers/hwmon/Kconfig

···
 
 config SENSORS_NTC_THERMISTOR
 	tristate "NTC thermistor support"
+	depends on (!OF && !IIO) || (OF && IIO)
 	help
 	  This driver supports NTC thermistors sensor reading and its
 	  interpretation. The driver can also monitor the temperature and

drivers/hwmon/ntc_thermistor.c

···
 #include <linux/math64.h>
 #include <linux/platform_device.h>
 #include <linux/err.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
 
 #include <linux/platform_data/ntc_thermistor.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/machine.h>
+#include <linux/iio/driver.h>
+#include <linux/iio/consumer.h>
 
 #include <linux/hwmon.h>
 #include <linux/hwmon-sysfs.h>
···
 struct ntc_compensation {
 	int		temp_C;
 	unsigned int	ohm;
+};
+
+static const struct platform_device_id ntc_thermistor_id[] = {
+	{ "ncp15wb473", TYPE_NCPXXWB473 },
+	{ "ncp18wb473", TYPE_NCPXXWB473 },
+	{ "ncp21wb473", TYPE_NCPXXWB473 },
+	{ "ncp03wb473", TYPE_NCPXXWB473 },
+	{ "ncp15wl333", TYPE_NCPXXWL333 },
+	{ },
 };
 
 /*
···
 	int n_comp;
 	char name[PLATFORM_NAME_SIZE];
 };
+
+#ifdef CONFIG_OF
+static int ntc_adc_iio_read(struct ntc_thermistor_platform_data *pdata)
+{
+	struct iio_channel *channel = pdata->chan;
+	unsigned int result;
+	int val, ret;
+
+	ret = iio_read_channel_raw(channel, &val);
+	if (ret < 0) {
+		pr_err("read channel() error: %d\n", ret);
+		return ret;
+	}
+
+	/* unit: mV */
+	result = pdata->pullup_uV * val;
+	result >>= 12;
+
+	return result;
+}
+
+static const struct of_device_id ntc_match[] = {
+	{ .compatible = "ntc,ncp15wb473",
+		.data = &ntc_thermistor_id[TYPE_NCPXXWB473] },
+	{ .compatible = "ntc,ncp18wb473",
+		.data = &ntc_thermistor_id[TYPE_NCPXXWB473] },
+	{ .compatible = "ntc,ncp21wb473",
+		.data = &ntc_thermistor_id[TYPE_NCPXXWB473] },
+	{ .compatible = "ntc,ncp03wb473",
+		.data = &ntc_thermistor_id[TYPE_NCPXXWB473] },
+	{ .compatible = "ntc,ncp15wl333",
+		.data = &ntc_thermistor_id[TYPE_NCPXXWL333] },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ntc_match);
+
+static struct ntc_thermistor_platform_data *
+ntc_thermistor_parse_dt(struct platform_device *pdev)
+{
+	struct iio_channel *chan;
+	struct device_node *np = pdev->dev.of_node;
+	struct ntc_thermistor_platform_data *pdata;
+
+	if (!np)
+		return NULL;
+
+	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
+	if (!pdata)
+		return ERR_PTR(-ENOMEM);
+
+	chan = iio_channel_get(&pdev->dev, NULL);
+	if (IS_ERR(chan))
+		return ERR_CAST(chan);
+
+	if (of_property_read_u32(np, "pullup-uv", &pdata->pullup_uV))
+		return ERR_PTR(-ENODEV);
+	if (of_property_read_u32(np, "pullup-ohm", &pdata->pullup_ohm))
+		return ERR_PTR(-ENODEV);
+	if (of_property_read_u32(np, "pulldown-ohm", &pdata->pulldown_ohm))
+		return ERR_PTR(-ENODEV);
+
+	if (of_find_property(np, "connected-positive", NULL))
+		pdata->connect = NTC_CONNECTED_POSITIVE;
+	else /* status change should be possible if not always on. */
+		pdata->connect = NTC_CONNECTED_GROUND;
+
+	pdata->chan = chan;
+	pdata->read_uV = ntc_adc_iio_read;
+
+	return pdata;
+}
+static void ntc_iio_channel_release(struct ntc_thermistor_platform_data *pdata)
+{
+	if (pdata->chan)
+		iio_channel_release(pdata->chan);
+}
+#else
+static struct ntc_thermistor_platform_data *
+ntc_thermistor_parse_dt(struct platform_device *pdev)
+{
+	return NULL;
+}
+
+static void ntc_iio_channel_release(struct ntc_thermistor_platform_data *pdata)
+{ }
+#endif
 
 static inline u64 div64_u64_safe(u64 dividend, u64 divisor)
 {
···
 		return data->pdata->read_ohm();
 
 	if (data->pdata->read_uV) {
-		read_uV = data->pdata->read_uV();
+		read_uV = data->pdata->read_uV(data->pdata);
 		if (read_uV < 0)
 			return read_uV;
 		return get_ohm_of_thermistor(data, read_uV);
···
 
 static int ntc_thermistor_probe(struct platform_device *pdev)
 {
+	const struct of_device_id *of_id =
+			of_match_device(of_match_ptr(ntc_match), &pdev->dev);
+	const struct platform_device_id *pdev_id;
+	struct ntc_thermistor_platform_data *pdata;
 	struct ntc_data *data;
-	struct ntc_thermistor_platform_data *pdata = pdev->dev.platform_data;
-	int ret = 0;
+	int ret;
+
+	pdata = ntc_thermistor_parse_dt(pdev);
+	if (IS_ERR(pdata))
+		return PTR_ERR(pdata);
+	else if (pdata == NULL)
+		pdata = pdev->dev.platform_data;
 
 	if (!pdata) {
 		dev_err(&pdev->dev, "No platform init data supplied.\n");
···
 	if (!data)
 		return -ENOMEM;
 
+	pdev_id = of_id ? of_id->data : platform_get_device_id(pdev);
+
 	data->dev = &pdev->dev;
 	data->pdata = pdata;
-	strlcpy(data->name, pdev->id_entry->name, sizeof(data->name));
+	strlcpy(data->name, pdev_id->name, sizeof(data->name));
 
-	switch (pdev->id_entry->driver_data) {
+	switch (pdev_id->driver_data) {
 	case TYPE_NCPXXWB473:
 		data->comp = ncpXXwb473;
 		data->n_comp = ARRAY_SIZE(ncpXXwb473);
···
 		break;
 	default:
 		dev_err(&pdev->dev, "Unknown device type: %lu(%s)\n",
-				pdev->id_entry->driver_data,
-				pdev->id_entry->name);
+				pdev_id->driver_data, pdev_id->name);
 		return -EINVAL;
 	}
 
···
 		goto err_after_sysfs;
 	}
 
-	dev_info(&pdev->dev, "Thermistor %s:%d (type: %s/%lu) successfully probed.\n",
-			pdev->name, pdev->id, pdev->id_entry->name,
-			pdev->id_entry->driver_data);
+	dev_info(&pdev->dev, "Thermistor type: %s successfully probed.\n",
+								pdev->name);
+
 	return 0;
 err_after_sysfs:
 	sysfs_remove_group(&data->dev->kobj, &ntc_attr_group);
+	ntc_iio_channel_release(pdata);
 	return ret;
 }
 
 static int ntc_thermistor_remove(struct platform_device *pdev)
 {
 	struct ntc_data *data = platform_get_drvdata(pdev);
+	struct ntc_thermistor_platform_data *pdata = data->pdata;
 
 	hwmon_device_unregister(data->hwmon_dev);
 	sysfs_remove_group(&data->dev->kobj, &ntc_attr_group);
+	ntc_iio_channel_release(pdata);
 	platform_set_drvdata(pdev, NULL);
 
 	return 0;
 }
 
-static const struct platform_device_id ntc_thermistor_id[] = {
-	{ "ncp15wb473", TYPE_NCPXXWB473 },
-	{ "ncp18wb473", TYPE_NCPXXWB473 },
-	{ "ncp21wb473", TYPE_NCPXXWB473 },
-	{ "ncp03wb473", TYPE_NCPXXWB473 },
-	{ "ncp15wl333", TYPE_NCPXXWL333 },
-	{ },
-};
-
 static struct platform_driver ntc_thermistor_driver = {
 	.driver = {
 		.name = "ntc-thermistor",
 		.owner = THIS_MODULE,
+		.of_match_table = of_match_ptr(ntc_match),
 	},
 	.probe = ntc_thermistor_probe,
 	.remove = ntc_thermistor_remove,

include/linux/platform_data/ntc_thermistor.h

···
 #ifndef _LINUX_NTC_H
 #define _LINUX_NTC_H
 
+struct iio_channel;
+
 enum ntc_thermistor_type {
 	TYPE_NCPXXWB473,
 	TYPE_NCPXXWL333,
···
 	 * described at Documentation/hwmon/ntc_thermistor
 	 *
 	 * pullup/down_ohm: 0 for infinite / not-connected
+	 *
+	 * chan: iio_channel pointer to communicate with the ADC which the
+	 * thermistor is using for conversion of the analog values.
 	 */
-	int (*read_uV)(void);
+	int (*read_uV)(struct ntc_thermistor_platform_data *);
 	unsigned int pullup_uV;
 
 	unsigned int pullup_ohm;
 	unsigned int pulldown_ohm;
 	enum { NTC_CONNECTED_POSITIVE, NTC_CONNECTED_GROUND } connect;
+	struct iio_channel *chan;
 
 	int (*read_ohm)(void);
 };