[PATCH v1 3/4] iio: adc: ad7949: add support for internal vref

Liam Beguin
2021-07-08T23:56:47Z

From: Liam Beguin <lvb@xiphos.com>

Add support for selecting a custom reference voltage from the
devicetree. If an external source is used, a vref regulator should be
defined in the devicetree.

Signed-off-by: Liam Beguin <lvb@xiphos.com>
---
drivers/iio/adc/ad7949.c | 84 +++++++++++++++++++++++++++++++++-------
1 file changed, 69 insertions(+), 15 deletions(-)

diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
index bbc6b56330a3..3c1293922d2e 100644
--- a/drivers/iio/adc/ad7949.c
+++ b/drivers/iio/adc/ad7949.c
@@ -31,6 +31,7 @@
#define AD7949_CFG_VAL_BW_FULL 1
#define AD7949_CFG_VAL_BW_QUARTER 0
#define AD7949_CFG_BIT_REF GENMASK(5, 3)
+#define AD7949_CFG_VAL_REF_EXTERNAL BIT(1)
#define AD7949_CFG_BIT_SEQ GENMASK(2, 1)
#define AD7949_CFG_BIT_RBN BIT(0)

@@ -40,6 +41,33 @@ enum {
ID_AD7689,
};

+/**
+ * enum ad7949_ref - Reference selection
+ *
+ * AD7949_REF_INT_2500: Internal reference and temperature sensor enabled.
+ * Vref=2.5V, buffered output
+ * AD7949_REF_INT_4096: Internal reference and temperature sensor enabled.
+ * Vref=4.096V, buffered output
+ * AD7949_REF_EXT_TEMP: Use external reference, temperature sensor enabled.
+ * Internal buffer disabled
+ * AD7949_REF_EXT_TEMP_BUF: Use external reference, internal buffer and
+ * temperature sensor enabled.
+ * AD7949_REF_RSRV_4: Do not use
+ * AD7949_REF_RSRV_5: Do not use
+ * AD7949_REF_EXT: Use external reference, internal buffer and
+ * temperature sensor disabled.
+ * AD7949_REF_EXT_BUF: Use external reference, internal buffer enabled.
+ * Internal reference and temperature sensor disabled.
+ */
+enum ad7949_ref {
+ AD7949_REF_INT_2500 = 0,
+ AD7949_REF_INT_4096,
+ AD7949_REF_EXT_TEMP,
+ AD7949_REF_EXT_TEMP_BUF,
+ AD7949_REF_EXT = 6,
+ AD7949_REF_EXT_BUF,
+};
+
struct ad7949_adc_spec {
u8 num_channels;
u8 resolution;
@@ -55,6 +83,7 @@ static const struct ad7949_adc_spec ad7949_adc_spec[] = {
* struct ad7949_adc_chip - AD ADC chip
* @lock: protects write sequences
* @vref: regulator generating Vref
+ * @refsel: reference selection
* @indio_dev: reference to iio structure
* @spi: reference to spi structure
* @resolution: resolution of the chip
@@ -66,6 +95,7 @@ static const struct ad7949_adc_spec ad7949_adc_spec[] = {
struct ad7949_adc_chip {
struct mutex lock;
struct regulator *vref;
+ enum ad7949_ref refsel;
struct iio_dev *indio_dev;
struct spi_device *spi;
u8 resolution;
@@ -241,12 +271,28 @@ static int ad7949_spi_read_raw(struct iio_dev *indio_dev,
return IIO_VAL_INT;

case IIO_CHAN_INFO_SCALE:
- ret = regulator_get_voltage(ad7949_adc->vref);
- if (ret < 0)
- return ret;
+ switch (ad7949_adc->refsel) {
+ case AD7949_REF_INT_2500:
+ *val = 2500;
+ break;
+ case AD7949_REF_INT_4096:
+ *val = 4096;
+ break;
+ case AD7949_REF_EXT_TEMP:
+ case AD7949_REF_EXT_TEMP_BUF:
+ case AD7949_REF_EXT:
+ case AD7949_REF_EXT_BUF:
+ ret = regulator_get_voltage(ad7949_adc->vref);
+ if (ret < 0)
+ return ret;
+
+ /* convert value back to mV */
+ *val = ret / 1000;
+ break;
+ }

- *val = ret / 5000;
- return IIO_VAL_INT;
+ *val2 = (1 << ad7949_adc->resolution) - 1;
+ return IIO_VAL_FRACTIONAL;
}

return -EINVAL;
@@ -285,7 +331,7 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
FIELD_PREP(AD7949_CFG_BIT_INCC, AD7949_CFG_VAL_INCC_UNIPOLAR_GND) |
FIELD_PREP(AD7949_CFG_BIT_INX, ad7949_adc->current_channel) |
FIELD_PREP(AD7949_CFG_BIT_BW, AD7949_CFG_VAL_BW_FULL) |
- FIELD_PREP(AD7949_CFG_BIT_REF, AD7949_REF_EXT_BUF) |
+ FIELD_PREP(AD7949_CFG_BIT_REF, ad7949_adc->refsel) |
FIELD_PREP(AD7949_CFG_BIT_SEQ, 0x0) |
FIELD_PREP(AD7949_CFG_BIT_RBN, 1);

@@ -304,6 +350,7 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
static int ad7949_spi_probe(struct spi_device *spi)
{
struct device *dev = &spi->dev;
+ struct device_node *np = dev->of_node;
const struct ad7949_adc_spec *spec;
struct ad7949_adc_chip *ad7949_adc;
struct iio_dev *indio_dev;
@@ -315,6 +362,7 @@ static int ad7949_spi_probe(struct spi_device *spi)
return -ENOMEM;
}

+ indio_dev->dev.of_node = np;
indio_dev->info = &ad7949_spi_info;
indio_dev->name = spi_get_device_id(spi)->name;
indio_dev->modes = INDIO_DIRECT_MODE;
@@ -330,16 +378,22 @@ static int ad7949_spi_probe(struct spi_device *spi)
ad7949_adc->resolution = spec->resolution;
ad7949_set_bits_per_word(ad7949_adc);

- ad7949_adc->vref = devm_regulator_get(dev, "vref");
- if (IS_ERR(ad7949_adc->vref)) {
- dev_err(dev, "fail to request regulator\n");
- return PTR_ERR(ad7949_adc->vref);
- }
+ /* Set default devicetree parameters */
+ ad7949_adc->refsel = AD7949_REF_EXT_BUF;
+ of_property_read_u32(np, "adi,reference-select", &ad7949_adc->refsel);

- ret = regulator_enable(ad7949_adc->vref);
- if (ret < 0) {
- dev_err(dev, "fail to enable regulator\n");
- return ret;
+ if (ad7949_adc->refsel & AD7949_CFG_VAL_REF_EXTERNAL) {
+ ad7949_adc->vref = devm_regulator_get(dev, "vref");
+ if (IS_ERR(ad7949_adc->vref)) {
+ dev_err(dev, "fail to request regulator\n");
+ return PTR_ERR(ad7949_adc->vref);
+ }
+
+ ret = regulator_enable(ad7949_adc->vref);
+ if (ret < 0) {
+ dev_err(dev, "fail to enable regulator\n");
+ return ret;
+ }
}

mutex_init(&ad7949_adc->lock);
--
2.30.1.489.g328c10930387