iio: adc: ad4170-4: Add support for internal temperature sensor

The AD4170-4 has an internal temperature sensor that can be read using the
ADC. Whenever possible, configure an IIO channel to provide the chip's
temperature.

Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Link: https://patch.msgid.link/51abd3617dff088981f487b5bdd9e78b26f74929.1751289747.git.marcelo.schmitt@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Author: machschmitt

drivers/iio/adc/ad4170-4.c

@@ -870,6 +870,27 @@ static const struct iio_chan_spec ad4170_channel_template = {
 	},
 };
 
+static const struct iio_chan_spec ad4170_temp_channel_template = {
+	.type = IIO_TEMP,
+	.indexed = 0,
+	.channel = 17,
+	.channel2 = 17,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+			      BIT(IIO_CHAN_INFO_SCALE) |
+			      BIT(IIO_CHAN_INFO_OFFSET) |
+			      BIT(IIO_CHAN_INFO_CALIBSCALE) |
+			      BIT(IIO_CHAN_INFO_CALIBBIAS) |
+			      BIT(IIO_CHAN_INFO_SAMP_FREQ),
+	.info_mask_separate_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),
+	.scan_type = {
+		.sign = 's',
+		.realbits = 24,
+		.storagebits = 32,
+		.shift = 8,
+		.endianness = IIO_BE,
+	},
+};
+
 /*
  * Receives the number of a multiplexed AD4170 input (ain_n), and stores the
  * voltage (in µV) of the specified input into ain_voltage. If the input number
@@ -1172,9 +1193,27 @@ static int ad4170_read_raw(struct iio_dev *indio_dev,
 		return ret;
 	case IIO_CHAN_INFO_SCALE:
 		pga = FIELD_GET(AD4170_AFE_PGA_GAIN_MSK, setup->afe);
-		*val = chan_info->scale_tbl[pga][0];
-		*val2 = chan_info->scale_tbl[pga][1];
-		return IIO_VAL_INT_PLUS_NANO;
+		switch (chan->type) {
+		case IIO_VOLTAGE:
+			*val = chan_info->scale_tbl[pga][0];
+			*val2 = chan_info->scale_tbl[pga][1];
+			return IIO_VAL_INT_PLUS_NANO;
+
+		case IIO_TEMP:
+			/*
+			 * The scale_tbl converts output codes to mV units so
+			 * multiply by MILLI to make the factor convert to µV.
+			 * Then, apply the temperature sensor change sensitivity
+			 * of 477 μV/K. Finally, multiply the result by MILLI
+			 * again to comply with milli degrees Celsius IIO ABI.
+			 */
+			*val = 0;
+			*val2 = DIV_ROUND_CLOSEST(chan_info->scale_tbl[pga][1] * MILLI, 477) *
+						  MILLI;
+			return IIO_VAL_INT_PLUS_NANO;
+		default:
+			return -EINVAL;
+		}
 	case IIO_CHAN_INFO_OFFSET:
 		pga = FIELD_GET(AD4170_AFE_PGA_GAIN_MSK, setup->afe);
 		*val = chan_info->offset_tbl[pga];
@@ -1842,13 +1881,40 @@ static int ad4170_parse_channels(struct iio_dev *indio_dev)
 	if (num_channels > AD4170_MAX_CHANNELS)
 		return dev_err_probe(dev, -EINVAL, "Too many channels\n");
 
+	/* Add one for temperature */
+	num_channels = min(num_channels + 1, AD4170_MAX_CHANNELS);
+
 	chan_num = 0;
 	device_for_each_child_node_scoped(dev, child) {
 		ret = ad4170_parse_channel_node(indio_dev, child, chan_num++);
 		if (ret)
 			return ret;
 	}
 
+	/*
+	 * Add internal temperature sensor channel if the maximum number of
+	 * channels has not been reached.
+	 */
+	if (num_channels < AD4170_MAX_CHANNELS) {
+		struct ad4170_setup *setup = &st->chan_infos[chan_num].setup;
+
+		st->chans[chan_num] = ad4170_temp_channel_template;
+		st->chans[chan_num].address = chan_num;
+		st->chans[chan_num].scan_index = chan_num;
+
+		st->chan_infos[chan_num].setup_num = AD4170_INVALID_SETUP;
+		st->chan_infos[chan_num].initialized = true;
+
+		setup->afe |= FIELD_PREP(AD4170_AFE_REF_SELECT_MSK,
+					 AD4170_REF_AVDD);
+
+		ret = ad4170_get_input_range(st, &st->chans[chan_num], chan_num,
+					     AD4170_REF_AVDD);
+		if (ret < 0)
+			return dev_err_probe(dev, ret, "Invalid input config\n");
+
+		st->chan_infos[chan_num].input_range_uv = ret;
+	}
 	indio_dev->num_channels = num_channels;
 	indio_dev->channels = st->chans;