[PATCH v6 10/10] iio: adc: ad7124: Implement temperature measurement

Uwe Kleine-König
2024-12-06T17:29:31Z

If the maximal count of channels the driver supports isn't fully
utilized, add an attribute providing the internal temperature.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
---
drivers/iio/adc/ad7124.c | 112 +++++++++++++++++++++++++++++++--------
1 file changed, 91 insertions(+), 21 deletions(-)

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index 9405cb579324..d858bffd2628 100644
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -95,6 +95,10 @@
#define AD7124_MAX_CONFIGS 8
#define AD7124_MAX_CHANNELS 16

+/* AD7124 input sources */
+#define AD7124_INPUT_TEMPSENSOR 16
+#define AD7124_INPUT_AVSS 17
+
enum ad7124_ids {
ID_AD7124_4,
ID_AD7124_8,
@@ -589,26 +593,59 @@ static int ad7124_read_raw(struct iio_dev *indio_dev,

return IIO_VAL_INT;
case IIO_CHAN_INFO_SCALE:
- mutex_lock(&st->cfgs_lock);
+ switch (chan->type) {
+ case IIO_VOLTAGE:
+ mutex_lock(&st->cfgs_lock);

- idx = st->channels[chan->address].cfg.pga_bits;
- *val = st->channels[chan->address].cfg.vref_mv;
- if (st->channels[chan->address].cfg.bipolar)
- *val2 = chan->scan_type.realbits - 1 + idx;
- else
- *val2 = chan->scan_type.realbits + idx;
+ idx = st->channels[chan->address].cfg.pga_bits;
+ *val = st->channels[chan->address].cfg.vref_mv;
+ if (st->channels[chan->address].cfg.bipolar)
+ *val2 = chan->scan_type.realbits - 1 + idx;
+ else
+ *val2 = chan->scan_type.realbits + idx;
+
+ mutex_unlock(&st->cfgs_lock);
+ return IIO_VAL_FRACTIONAL_LOG2;
+
+ case IIO_TEMP:
+ /*
+ * According to the data sheet
+ * Temperature (°C)
+ * = ((Conversion − 0x800000)/13584) − 272.5
+ * = (Conversion − 0x800000 - 13584 * 272.5) / 13584
+ * = (Conversion − 12090248) / 13584
+ * So scale with 1000/13584 to yield °mC. Reduce by 8 to
+ * 125/1698.
+ */
+ *val = 125;
+ *val2 = 1698;
+ return IIO_VAL_FRACTIONAL;
+
+ default:
+ return -EINVAL;
+ }

- mutex_unlock(&st->cfgs_lock);
- return IIO_VAL_FRACTIONAL_LOG2;
case IIO_CHAN_INFO_OFFSET:
- mutex_lock(&st->cfgs_lock);
- if (st->channels[chan->address].cfg.bipolar)
- *val = -(1 << (chan->scan_type.realbits - 1));
- else
- *val = 0;
+ switch (chan->type) {
+ case IIO_VOLTAGE:
+ mutex_lock(&st->cfgs_lock);
+ if (st->channels[chan->address].cfg.bipolar)
+ *val = -(1 << (chan->scan_type.realbits - 1));
+ else
+ *val = 0;
+
+ mutex_unlock(&st->cfgs_lock);
+ return IIO_VAL_INT;
+
+ case IIO_TEMP:
+ /* see calculation above */
+ *val = -12090248;
+ return IIO_VAL_INT;
+
+ default:
+ return -EINVAL;
+ }

- mutex_unlock(&st->cfgs_lock);
- return IIO_VAL_INT;
case IIO_CHAN_INFO_SAMP_FREQ:
mutex_lock(&st->cfgs_lock);
*val = st->channels[chan->address].cfg.odr;
@@ -826,11 +863,10 @@ static int ad7124_parse_channel_config(struct iio_dev *indio_dev,
struct ad7124_channel *channels;
struct iio_chan_spec *chan;
unsigned int ain[2], channel = 0, tmp;
+ unsigned int num_channels;
int ret;

- st->num_channels = device_get_child_node_count(dev);
- if (!st->num_channels)
- return dev_err_probe(dev, -ENODEV, "no channel children\n");
+ num_channels = device_get_child_node_count(dev);

/*
* The driver assigns each logical channel defined in the device tree
@@ -839,9 +875,12 @@ static int ad7124_parse_channel_config(struct iio_dev *indio_dev,
* CHANNEL_15) as an additional channel register. The driver could be
* improved to lift this limitation.
*/
- if (st->num_channels > AD7124_MAX_CHANNELS)
+ if (num_channels > AD7124_MAX_CHANNELS)
return dev_err_probe(dev, -EINVAL, "Too many channels defined\n");

+ /* Add one for temperature */
+ st->num_channels = min(num_channels + 1, AD7124_MAX_CHANNELS);
+
chan = devm_kcalloc(indio_dev->dev.parent, st->num_channels,
sizeof(*chan), GFP_KERNEL);
if (!chan)
@@ -862,7 +901,7 @@ static int ad7124_parse_channel_config(struct iio_dev *indio_dev,
return dev_err_probe(dev, ret,
"Failed to parse reg property of %pfwP\n", child);

- if (channel >= indio_dev->num_channels)
+ if (channel >= num_channels)
return dev_err_probe(dev, -EINVAL,
"Channel index >= number of channels in %pfwP\n", child);

@@ -902,6 +941,37 @@ static int ad7124_parse_channel_config(struct iio_dev *indio_dev,
chan[channel].channel2 = ain[1];
}

+ if (num_channels < AD7124_MAX_CHANNELS) {
+ st->channels[num_channels] = (struct ad7124_channel) {
+ .nr = num_channels,
+ .ain = AD7124_CHANNEL_AINP(AD7124_INPUT_TEMPSENSOR) |
+ AD7124_CHANNEL_AINM(AD7124_INPUT_AVSS),
+ .cfg = {
+ .bipolar = true,
+ },
+ };
+
+ chan[num_channels] = (struct iio_chan_spec) {
+ .type = IIO_TEMP,
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+ BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET) |
+ BIT(IIO_CHAN_INFO_SAMP_FREQ),
+ .scan_type = {
+ /*
+ * You might find it strange that a bipolar
+ * measurement yields an unsigned value, but
+ * this matches the device's manual.
+ */
+ .sign = 'u',
+ .realbits = 24,
+ .storagebits = 32,
+ .endianness = IIO_BE,
+ },
+ .address = num_channels,
+ .scan_index = num_channels,
+ };
+ };
+
return 0;
}

--
2.45.2