[PATCH v2 6/7] iio: adc: ad4170: Add support for internal temperature sensor

Marcelo Schmitt
2025-04-28T12:29:41Z

The AD4170 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>
---
changes since v1:
- Dropped a unneeded comment
- Collected review tag

drivers/iio/adc/ad4170.c | 72 ++++++++++++++++++++++++++++++++++++++--
1 file changed, 69 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/adc/ad4170.c b/drivers/iio/adc/ad4170.c
index 612676c1c88a..335b4194c7eb 100644
--- a/drivers/iio/adc/ad4170.c
+++ b/drivers/iio/adc/ad4170.c
@@ -891,6 +891,27 @@ 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
@@ -1189,9 +1210,27 @@ 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];
@@ -1852,12 +1891,39 @@ 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);
+
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;
return 0;
--
2.47.2