[PATCH v7 4/7] iio: adc: ad7380: add support for pseudo-differential parts

Julien Stephan
2024-05-28T14:20:42Z

From: David Lechner <dlechner@baylibre.com>

Add support for AD7383, AD7384 pseudo-differential compatible parts.
Pseudo differential parts require common mode voltage supplies so add
the support for them and add the support of IIO_CHAN_INFO_OFFSET to
retrieve the offset

Signed-off-by: David Lechner <dlechner@baylibre.com>
Signed-off-by: Julien Stephan <jstephan@baylibre.com>
---
drivers/iio/adc/ad7380.c | 110 ++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 94 insertions(+), 16 deletions(-)

diff --git a/drivers/iio/adc/ad7380.c b/drivers/iio/adc/ad7380.c
index dac7e11755ff..4ad283cf970d 100644
--- a/drivers/iio/adc/ad7380.c
+++ b/drivers/iio/adc/ad7380.c
@@ -7,6 +7,7 @@
*
* Datasheets of supported parts:
* ad7380/1 : https://www.analog.com/media/en/technical-documentation/data-sheets/AD7380-7381.pdf
+ * ad7383/4 : https://www.analog.com/media/en/technical-documentation/data-sheets/ad7383-7384.pdf
*/

#include <linux/bitfield.h>
@@ -66,16 +67,19 @@ struct ad7380_chip_info {
const char *name;
const struct iio_chan_spec *channels;
unsigned int num_channels;
+ const char * const *vcm_supplies;
+ unsigned int num_vcm_supplies;
};

-#define AD7380_CHANNEL(index, bits) { \
+#define AD7380_CHANNEL(index, bits, diff) { \
.type = IIO_VOLTAGE, \
- .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
+ ((diff) ? 0 : BIT(IIO_CHAN_INFO_OFFSET)), \
.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
.indexed = 1, \
- .differential = 1, \
- .channel = 2 * (index), \
- .channel2 = 2 * (index) + 1, \
+ .differential = (diff), \
+ .channel = (diff) ? (2 * (index)) : (index), \
+ .channel2 = (diff) ? (2 * (index) + 1) : 0, \
.scan_index = (index), \
.scan_type = { \
.sign = 's', \
@@ -85,15 +89,23 @@ struct ad7380_chip_info {
}, \
}

-#define DEFINE_AD7380_2_CHANNEL(name, bits) \
-static const struct iio_chan_spec name[] = { \
- AD7380_CHANNEL(0, bits), \
- AD7380_CHANNEL(1, bits), \
- IIO_CHAN_SOFT_TIMESTAMP(2), \
+#define DEFINE_AD7380_2_CHANNEL(name, bits, diff) \
+static const struct iio_chan_spec name[] = { \
+ AD7380_CHANNEL(0, bits, diff), \
+ AD7380_CHANNEL(1, bits, diff), \
+ IIO_CHAN_SOFT_TIMESTAMP(2), \
}

-DEFINE_AD7380_2_CHANNEL(ad7380_channels, 16);
-DEFINE_AD7380_2_CHANNEL(ad7381_channels, 14);
+/* fully differential */
+DEFINE_AD7380_2_CHANNEL(ad7380_channels, 16, 1);
+DEFINE_AD7380_2_CHANNEL(ad7381_channels, 14, 1);
+/* pseudo differential */
+DEFINE_AD7380_2_CHANNEL(ad7383_channels, 16, 0);
+DEFINE_AD7380_2_CHANNEL(ad7384_channels, 14, 0);
+
+static const char * const ad7380_2_channel_vcm_supplies[] = {
+ "aina", "ainb",
+};

/* Since this is simultaneous sampling, we don't allow individual channels. */
static const unsigned long ad7380_2_channel_scan_masks[] = {
@@ -113,11 +125,28 @@ static const struct ad7380_chip_info ad7381_chip_info = {
.num_channels = ARRAY_SIZE(ad7381_channels),
};

+static const struct ad7380_chip_info ad7383_chip_info = {
+ .name = "ad7383",
+ .channels = ad7383_channels,
+ .num_channels = ARRAY_SIZE(ad7383_channels),
+ .vcm_supplies = ad7380_2_channel_vcm_supplies,
+ .num_vcm_supplies = ARRAY_SIZE(ad7380_2_channel_vcm_supplies),
+};
+
+static const struct ad7380_chip_info ad7384_chip_info = {
+ .name = "ad7384",
+ .channels = ad7384_channels,
+ .num_channels = ARRAY_SIZE(ad7384_channels),
+ .vcm_supplies = ad7380_2_channel_vcm_supplies,
+ .num_vcm_supplies = ARRAY_SIZE(ad7380_2_channel_vcm_supplies),
+};
+
struct ad7380_state {
const struct ad7380_chip_info *chip_info;
struct spi_device *spi;
struct regmap *regmap;
unsigned int vref_mv;
+ unsigned int vcm_mv[2];
/*
* DMA (thus cache coherency maintenance) requires the
* transfer buffers to live in their own cache lines.
@@ -288,13 +317,24 @@ static int ad7380_read_raw(struct iio_dev *indio_dev,
unreachable();
case IIO_CHAN_INFO_SCALE:
/*
- * According to the datasheet, the LSB size for fully differential ADC is
- * (2 × VREF) / 2^N, where N is the ADC resolution (i.e realbits)
+ * According to the datasheet, the LSB size is:
+ * * (2 × VREF) / 2^N, for differential chips
+ * * VREF / 2^N, for pseudo-differential chips
+ * where N is the ADC resolution (i.e realbits)
*/
*val = st->vref_mv;
- *val2 = chan->scan_type.realbits - 1;
+ *val2 = chan->scan_type.realbits - chan->differential;

return IIO_VAL_FRACTIONAL_LOG2;
+ case IIO_CHAN_INFO_OFFSET:
+ /*
+ * According to IIO ABI, offset is applied before scale,
+ * so offset is: vcm_mv / scale
+ */
+ *val = st->vcm_mv[chan->channel] * (1 << chan->scan_type.realbits)
+ / st->vref_mv;
+
+ return IIO_VAL_INT;
default:
return -EINVAL;
}
@@ -341,7 +381,7 @@ static int ad7380_probe(struct spi_device *spi)
struct iio_dev *indio_dev;
struct ad7380_state *st;
struct regulator *vref;
- int ret;
+ int ret, i;

indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
if (!indio_dev)
@@ -385,6 +425,40 @@ static int ad7380_probe(struct spi_device *spi)
st->vref_mv = AD7380_INTERNAL_REF_MV;
}

+ if (st->chip_info->num_vcm_supplies > ARRAY_SIZE(st->vcm_mv))
+ return dev_err_probe(&spi->dev, -EINVAL,
+ "invalid number of VCM supplies\n");
+
+ /*
+ * pseudo-differential chips have common mode supplies for the negative
+ * input pin.
+ */
+ for (i = 0; i < st->chip_info->num_vcm_supplies; i++) {
+ struct regulator *vcm;
+
+ vcm = devm_regulator_get(&spi->dev,
+ st->chip_info->vcm_supplies[i]);
+ if (IS_ERR(vcm))
+ return dev_err_probe(&spi->dev, PTR_ERR(vcm),
+ "Failed to get %s regulator\n",
+ st->chip_info->vcm_supplies[i]);
+
+ ret = regulator_enable(vcm);
+ if (ret)
+ return ret;
+
+ ret = devm_add_action_or_reset(&spi->dev,
+ ad7380_regulator_disable, vcm);
+ if (ret)
+ return ret;
+
+ ret = regulator_get_voltage(vcm);
+ if (ret < 0)
+ return ret;
+
+ st->vcm_mv[i] = ret / 1000;
+ }
+
st->regmap = devm_regmap_init(&spi->dev, NULL, st, &ad7380_regmap_config);
if (IS_ERR(st->regmap))
return dev_err_probe(&spi->dev, PTR_ERR(st->regmap),
@@ -413,12 +487,16 @@ static int ad7380_probe(struct spi_device *spi)
static const struct of_device_id ad7380_of_match_table[] = {
{ .compatible = "adi,ad7380", .data = &ad7380_chip_info },
{ .compatible = "adi,ad7381", .data = &ad7381_chip_info },
+ { .compatible = "adi,ad7383", .data = &ad7383_chip_info },
+ { .compatible = "adi,ad7384", .data = &ad7384_chip_info },
{ }
};

static const struct spi_device_id ad7380_id_table[] = {
{ "ad7380", (kernel_ulong_t)&ad7380_chip_info },
{ "ad7381", (kernel_ulong_t)&ad7381_chip_info },
+ { "ad7383", (kernel_ulong_t)&ad7383_chip_info },
+ { "ad7384", (kernel_ulong_t)&ad7384_chip_info },
{ }
};
MODULE_DEVICE_TABLE(spi, ad7380_id_table);

--
2.44.0