[PATCH v4 2/3] iio: adc: ltc2497: add support for LTC2495

@@ -12,6 +12,7 @@
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/regulator/consumer.h>
+#include <linux/units.h>
 
 #include "ltc2497.h"
 

@@ -46,7 +47,8 @@ static int ltc2497core_wait_conv(struct ltc2497core_driverdata *ddata)
 	return 1;
 }
 
-static int ltc2497core_read(struct ltc2497core_driverdata *ddata, u8 address, int *val)
+static int ltc2497core_read(struct ltc2497core_driverdata *ddata, u8 address,
+			    enum iio_chan_type type, int *val)
 {
 	int ret;
 

@@ -54,11 +56,13 @@ static int ltc2497core_read(struct ltc2497core_driverdata *ddata, u8 address, in
 	if (ret < 0)
 		return ret;
 
-	if (ret || ddata->addr_prev != address) {
+	if (ret || ddata->addr_prev != address ||
+	    ddata->chan_type_prev != type) {
 		ret = ddata->result_and_measure(ddata, address, NULL);
 		if (ret < 0)
 			return ret;
 		ddata->addr_prev = address;
+		ddata->chan_type_prev = type;
 
 		if (msleep_interruptible(LTC2497_CONVERSION_TIME_MS))
 			return -ERESTARTSYS;

@@ -83,7 +87,7 @@ static int ltc2497core_read_raw(struct iio_dev *indio_dev,
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
 		mutex_lock(&ddata->lock);
-		ret = ltc2497core_read(ddata, chan->address, val);
+		ret = ltc2497core_read(ddata, chan->address, chan->type, val);
 		mutex_unlock(&ddata->lock);
 		if (ret < 0)
 			return ret;

@@ -95,10 +99,37 @@ static int ltc2497core_read_raw(struct iio_dev *indio_dev,
 		if (ret < 0)
 			return ret;
 
-		*val = ret / 1000;
-		*val2 = ddata->chip_info->resolution + 1;
+		switch (chan->type) {
+		case IIO_VOLTAGE:
+			*val = ret / 1000;
+			*val2 = ddata->chip_info->resolution + 1;
 
-		return IIO_VAL_FRACTIONAL_LOG2;
+			return IIO_VAL_FRACTIONAL_LOG2;
+
+		case IIO_TEMP:
+			if (!ddata->chip_info->has_temp_channel)
+				return -EINVAL;
+
+			*val = ret;
+			*val2 = ddata->chip_info->temp_scale_mV;
+
+			return IIO_VAL_FRACTIONAL;
+
+		default:
+			return -EINVAL;
+		}
+	case IIO_CHAN_INFO_OFFSET:
+		if (chan->type != IIO_TEMP)
+			return -EINVAL;
+
+		ret = regulator_get_voltage(ddata->ref);
+		if (ret < 0)
+			return ret;
+
+		*val = kelvin_to_celsius(0) * ddata->chip_info->temp_scale_mV;
+		*val2 = ret / 1000;
+
+		return IIO_VAL_FRACTIONAL;
 
 	default:
 		return -EINVAL;

@@ -126,39 +157,54 @@ static int ltc2497core_read_raw(struct iio_dev *indio_dev,
 	.differential = 1, \
 }
 
+#define LTC2497_TEMPERATURE_CHAN \
+{												\
+	.type = IIO_TEMP,									\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),						\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),	\
+}
+
+#define LTC2497_VOLTAGE_CHANNEL_LIST \
+	LTC2497_CHAN(0, LTC2497_SGL, "CH0"),			\
+	LTC2497_CHAN(1, LTC2497_SGL, "CH1"),			\
+	LTC2497_CHAN(2, LTC2497_SGL, "CH2"),			\
+	LTC2497_CHAN(3, LTC2497_SGL, "CH3"),			\
+	LTC2497_CHAN(4, LTC2497_SGL, "CH4"),			\
+	LTC2497_CHAN(5, LTC2497_SGL, "CH5"),			\
+	LTC2497_CHAN(6, LTC2497_SGL, "CH6"),			\
+	LTC2497_CHAN(7, LTC2497_SGL, "CH7"),			\
+	LTC2497_CHAN(8, LTC2497_SGL, "CH8"),			\
+	LTC2497_CHAN(9, LTC2497_SGL, "CH9"),			\
+	LTC2497_CHAN(10, LTC2497_SGL, "CH10"),			\
+	LTC2497_CHAN(11, LTC2497_SGL, "CH11"),			\
+	LTC2497_CHAN(12, LTC2497_SGL, "CH12"),			\
+	LTC2497_CHAN(13, LTC2497_SGL, "CH13"),			\
+	LTC2497_CHAN(14, LTC2497_SGL, "CH14"),			\
+	LTC2497_CHAN(15, LTC2497_SGL, "CH15"),			\
+	LTC2497_CHAN_DIFF(0, LTC2497_DIFF),			\
+	LTC2497_CHAN_DIFF(1, LTC2497_DIFF),			\
+	LTC2497_CHAN_DIFF(2, LTC2497_DIFF),			\
+	LTC2497_CHAN_DIFF(3, LTC2497_DIFF),			\
+	LTC2497_CHAN_DIFF(4, LTC2497_DIFF),			\
+	LTC2497_CHAN_DIFF(5, LTC2497_DIFF),			\
+	LTC2497_CHAN_DIFF(6, LTC2497_DIFF),			\
+	LTC2497_CHAN_DIFF(7, LTC2497_DIFF),			\
+	LTC2497_CHAN_DIFF(0, LTC2497_DIFF | LTC2497_SIGN),	\
+	LTC2497_CHAN_DIFF(1, LTC2497_DIFF | LTC2497_SIGN),	\
+	LTC2497_CHAN_DIFF(2, LTC2497_DIFF | LTC2497_SIGN),	\
+	LTC2497_CHAN_DIFF(3, LTC2497_DIFF | LTC2497_SIGN),	\
+	LTC2497_CHAN_DIFF(4, LTC2497_DIFF | LTC2497_SIGN),	\
+	LTC2497_CHAN_DIFF(5, LTC2497_DIFF | LTC2497_SIGN),	\
+	LTC2497_CHAN_DIFF(6, LTC2497_DIFF | LTC2497_SIGN),	\
+	LTC2497_CHAN_DIFF(7, LTC2497_DIFF | LTC2497_SIGN)
+
 static const struct iio_chan_spec ltc2497core_channel[] = {
-	LTC2497_CHAN(0, LTC2497_SGL, "CH0"),
-	LTC2497_CHAN(1, LTC2497_SGL, "CH1"),
-	LTC2497_CHAN(2, LTC2497_SGL, "CH2"),
-	LTC2497_CHAN(3, LTC2497_SGL, "CH3"),
-	LTC2497_CHAN(4, LTC2497_SGL, "CH4"),
-	LTC2497_CHAN(5, LTC2497_SGL, "CH5"),
-	LTC2497_CHAN(6, LTC2497_SGL, "CH6"),
-	LTC2497_CHAN(7, LTC2497_SGL, "CH7"),
-	LTC2497_CHAN(8, LTC2497_SGL, "CH8"),
-	LTC2497_CHAN(9, LTC2497_SGL, "CH9"),
-	LTC2497_CHAN(10, LTC2497_SGL, "CH10"),
-	LTC2497_CHAN(11, LTC2497_SGL, "CH11"),
-	LTC2497_CHAN(12, LTC2497_SGL, "CH12"),
-	LTC2497_CHAN(13, LTC2497_SGL, "CH13"),
-	LTC2497_CHAN(14, LTC2497_SGL, "CH14"),
-	LTC2497_CHAN(15, LTC2497_SGL, "CH15"),
-	LTC2497_CHAN_DIFF(0, LTC2497_DIFF),
-	LTC2497_CHAN_DIFF(1, LTC2497_DIFF),
-	LTC2497_CHAN_DIFF(2, LTC2497_DIFF),
-	LTC2497_CHAN_DIFF(3, LTC2497_DIFF),
-	LTC2497_CHAN_DIFF(4, LTC2497_DIFF),
-	LTC2497_CHAN_DIFF(5, LTC2497_DIFF),
-	LTC2497_CHAN_DIFF(6, LTC2497_DIFF),
-	LTC2497_CHAN_DIFF(7, LTC2497_DIFF),
-	LTC2497_CHAN_DIFF(0, LTC2497_DIFF | LTC2497_SIGN),
-	LTC2497_CHAN_DIFF(1, LTC2497_DIFF | LTC2497_SIGN),
-	LTC2497_CHAN_DIFF(2, LTC2497_DIFF | LTC2497_SIGN),
-	LTC2497_CHAN_DIFF(3, LTC2497_DIFF | LTC2497_SIGN),
-	LTC2497_CHAN_DIFF(4, LTC2497_DIFF | LTC2497_SIGN),
-	LTC2497_CHAN_DIFF(5, LTC2497_DIFF | LTC2497_SIGN),
-	LTC2497_CHAN_DIFF(6, LTC2497_DIFF | LTC2497_SIGN),
-	LTC2497_CHAN_DIFF(7, LTC2497_DIFF | LTC2497_SIGN),
+	LTC2497_VOLTAGE_CHANNEL_LIST,
+};
+
+static const struct iio_chan_spec ltc2497core_channel_with_temperature[] = {
+	LTC2497_VOLTAGE_CHANNEL_LIST,
+	LTC2497_TEMPERATURE_CHAN,
 };
 
 static const struct iio_info ltc2497core_info = {

@@ -182,8 +228,14 @@ int ltc2497core_probe(struct device *dev, struct iio_dev *indio_dev)
 
 	indio_dev->info = &ltc2497core_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
-	indio_dev->channels = ltc2497core_channel;
-	indio_dev->num_channels = ARRAY_SIZE(ltc2497core_channel);
+
+	if (ddata->chip_info->has_temp_channel) {
+		indio_dev->channels = ltc2497core_channel_with_temperature;
+		indio_dev->num_channels = ARRAY_SIZE(ltc2497core_channel_with_temperature);
+	} else {
+		indio_dev->channels = ltc2497core_channel;
+		indio_dev->num_channels = ARRAY_SIZE(ltc2497core_channel);
+	}
 
 	ret = ddata->result_and_measure(ddata, LTC2497_CONFIG_DEFAULT, NULL);
 	if (ret < 0)

@@ -18,7 +18,12 @@
 
 #include "ltc2497.h"
 
+/* Optional second byte fields for LTC2495 and LTC2499 */
+#define LTC2497_EN2	BIT(7)
+#define LTC2497_IM	BIT(6)
+
 enum ltc2497_chip_type {
+	TYPE_LTC2495,
 	TYPE_LTC2497,
 	TYPE_LTC2499,
 };

@@ -85,8 +90,28 @@ static int ltc2497_result_and_measure(struct ltc2497core_driverdata *ddata,
 			return 0;
 	}
 
-	ret = i2c_smbus_write_byte(st->client,
-				   LTC2497_ENABLE | address);
+	/*
+	 * Chips with temperature sensor support (e.g., LTC2495/LTC2499)
+	 * require a two-byte command format to select any channel.
+	 *
+	 * To read the internal temperature, LTC2497_EN2 and LTC2497_IM
+	 * are sent as the second byte. To read a voltage channel, LTC2497_EN2
+	 * is sent, which sets the default configuration: simultaneous 50/60Hz
+	 * rejection, 1x speed, and gain=1.
+	 *
+	 * Chips without this feature use a standard single-byte command.
+	 */
+	if (ddata->chip_info->has_temp_channel) {
+		if (ddata->chan_type_prev == IIO_TEMP)
+			ret = i2c_smbus_write_byte_data(st->client, LTC2497_ENABLE,
+							LTC2497_EN2 | LTC2497_IM);
+		else
+			ret = i2c_smbus_write_byte_data(st->client, LTC2497_ENABLE | address,
+							LTC2497_EN2);
+	} else {
+		ret = i2c_smbus_write_byte(st->client, LTC2497_ENABLE | address);
+	}
+
 	if (ret)
 		dev_err(&st->client->dev, "i2c transfer failed: %pe\n",
 			ERR_PTR(ret));

@@ -131,6 +156,12 @@ static void ltc2497_remove(struct i2c_client *client)
 }
 
 static const struct ltc2497_chip_info ltc2497_info[] = {
+	[TYPE_LTC2495] = {
+		.resolution = 16,
+		.name = "ltc2495",
+		.has_temp_channel = true,
+		.temp_scale_mV = 12250,
+	},
 	[TYPE_LTC2497] = {
 		.resolution = 16,
 		.name = NULL,

@@ -138,10 +169,13 @@ static const struct ltc2497_chip_info ltc2497_info[] = {
 	[TYPE_LTC2499] = {
 		.resolution = 24,
 		.name = "ltc2499",
+		.has_temp_channel = true,
+		.temp_scale_mV = 1570000,
 	},
 };
 
 static const struct i2c_device_id ltc2497_id[] = {
+	{ "ltc2495", (kernel_ulong_t)&ltc2497_info[TYPE_LTC2495] },
 	{ "ltc2497", (kernel_ulong_t)&ltc2497_info[TYPE_LTC2497] },
 	{ "ltc2499", (kernel_ulong_t)&ltc2497_info[TYPE_LTC2499] },
 	{ }

@@ -149,6 +183,7 @@ static const struct i2c_device_id ltc2497_id[] = {
 MODULE_DEVICE_TABLE(i2c, ltc2497_id);
 
 static const struct of_device_id ltc2497_of_match[] = {
+	{ .compatible = "lltc,ltc2495", .data = &ltc2497_info[TYPE_LTC2495] },
 	{ .compatible = "lltc,ltc2497", .data = &ltc2497_info[TYPE_LTC2497] },
 	{ .compatible = "lltc,ltc2499", .data = &ltc2497_info[TYPE_LTC2499] },
 	{ }

@@ -7,6 +7,16 @@
 struct ltc2497_chip_info {
 	u32 resolution;
 	const char *name;
+	/*
+	 * Represents the datasheet constant from the temperature formula:
+	 * T_Kelvin = (DATAOUT * Vref) / temp_scale, where Vref is in Volts.
+	 *
+	 * To allow the driver to use Vref in millivolts for the calculation
+	 * and also to avoid floating points, this stored value represents the
+	 * datasheet constant scaled by 1000.
+	 */
+	u32 temp_scale_mV;
+	bool has_temp_channel;
 };
 
 struct ltc2497core_driverdata {

@@ -18,6 +28,7 @@ struct ltc2497core_driverdata {
 	u8 addr_prev;
 	int (*result_and_measure)(struct ltc2497core_driverdata *ddata,
 				  u8 address, int *val);
+	enum iio_chan_type chan_type_prev;
 };
 
 int ltc2497core_probe(struct device *dev, struct iio_dev *indio_dev);