[PATCH v4 3/5] iio: adc: ad7949: add support for internal vref

Liam Beguin
2021-07-27T23:29:29Z

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 | 132 +++++++++++++++++++++++++++++++++------
1 file changed, 114 insertions(+), 18 deletions(-)

diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
index f1702c54c8be..eaea8f5e87d8 100644
--- a/drivers/iio/adc/ad7949.c
+++ b/drivers/iio/adc/ad7949.c
@@ -35,7 +35,11 @@

/* REF: reference/buffer selection */
#define AD7949_CFG_BIT_REF GENMASK(5, 3)
-#define AD7949_CFG_VAL_REF_EXT_BUF 7
+#define AD7949_CFG_VAL_REF_EXT_TEMP_BUF 3
+#define AD7949_CFG_VAL_REF_EXT_TEMP 2
+#define AD7949_CFG_VAL_REF_INT_4096 1
+#define AD7949_CFG_VAL_REF_INT_2500 0
+#define AD7949_CFG_VAL_REF_EXTERNAL BIT(1)

/* SEQ: channel sequencer. Allows for scanning channels */
#define AD7949_CFG_BIT_SEQ GENMASK(2, 1)
@@ -60,6 +64,14 @@ static const struct ad7949_adc_spec ad7949_adc_spec[] = {
[ID_AD7689] = { .num_channels = 8, .resolution = 16 },
};

+/**
+ * struct ad7949_channel - ADC Channel parameters
+ * @refsel: reference selection
+ */
+struct ad7949_channel {
+ u32 refsel;
+};
+
/**
* struct ad7949_adc_chip - AD ADC chip
* @lock: protects write sequences
@@ -77,6 +89,7 @@ struct ad7949_adc_chip {
struct regulator *vref;
struct iio_dev *indio_dev;
struct spi_device *spi;
+ struct ad7949_channel *channels;
u8 resolution;
u8 bits_per_word;
u16 cfg;
@@ -133,6 +146,7 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
int ret;
int i;
struct spi_message msg;
+ struct ad7949_channel *ad7949_chan = &ad7949_adc->channels[channel];
struct spi_transfer tx[] = {
{
.rx_buf = &ad7949_adc->buffer,
@@ -149,8 +163,9 @@ static int ad7949_spi_read_channel(struct ad7949_adc_chip *ad7949_adc, int *val,
*/
for (i = 0; i < 2; i++) {
ret = ad7949_spi_write_cfg(ad7949_adc,
- FIELD_PREP(AD7949_CFG_BIT_INX, channel),
- AD7949_CFG_BIT_INX);
+ FIELD_PREP(AD7949_CFG_BIT_INX, channel) |
+ FIELD_PREP(AD7949_CFG_BIT_REF, ad7949_chan->refsel),
+ AD7949_CFG_BIT_INX | AD7949_CFG_BIT_REF);
if (ret)
return ret;
if (channel == ad7949_adc->current_channel)
@@ -219,6 +234,7 @@ static int ad7949_spi_read_raw(struct iio_dev *indio_dev,
int *val, int *val2, long mask)
{
struct ad7949_adc_chip *ad7949_adc = iio_priv(indio_dev);
+ struct ad7949_channel *ad7949_chan = &ad7949_adc->channels[chan->channel];
int ret;

if (!val)
@@ -236,12 +252,26 @@ 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_chan->refsel) {
+ case AD7949_CFG_VAL_REF_INT_2500:
+ *val = 2500;
+ break;
+ case AD7949_CFG_VAL_REF_INT_4096:
+ *val = 4096;
+ break;
+ case AD7949_CFG_VAL_REF_EXT_TEMP:
+ case AD7949_CFG_VAL_REF_EXT_TEMP_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;
@@ -280,7 +310,7 @@ 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_FULL, 1) |
- FIELD_PREP(AD7949_CFG_BIT_REF, AD7949_CFG_VAL_REF_EXT_BUF) |
+ FIELD_PREP(AD7949_CFG_BIT_REF, ad7949_adc->channels[0].refsel) |
FIELD_PREP(AD7949_CFG_BIT_SEQ, 0x0) |
FIELD_PREP(AD7949_CFG_BIT_RBN, 1);

@@ -296,14 +326,24 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
return ret;
}

+static void ad7949_disable_reg(void *reg)
+{
+ regulator_disable(reg);
+}
+
static int ad7949_spi_probe(struct spi_device *spi)
{
u32 spi_ctrl_mask = spi->controller->bits_per_word_mask;
struct device *dev = &spi->dev;
const struct ad7949_adc_spec *spec;
struct ad7949_adc_chip *ad7949_adc;
+ struct ad7949_channel *ad7949_chan;
+ struct fwnode_handle *child;
struct iio_dev *indio_dev;
+ int mode;
+ u32 tmp;
int ret;
+ int i;

indio_dev = devm_iio_device_alloc(dev, sizeof(*ad7949_adc));
if (!indio_dev) {
@@ -337,16 +377,74 @@ static int ad7949_spi_probe(struct spi_device *spi)
return -EINVAL;
}

- ad7949_adc->vref = devm_regulator_get(dev, "vref");
+ /* Setup external voltage ref, buffered? */
+ ad7949_adc->vref = devm_regulator_get(dev, "vrefin");
if (IS_ERR(ad7949_adc->vref)) {
- dev_err(dev, "fail to request regulator\n");
- return PTR_ERR(ad7949_adc->vref);
+ /* unbuffered? */
+ ad7949_adc->vref = devm_regulator_get(dev, "vref");
+ if (IS_ERR(ad7949_adc->vref)) {
+ /* Internal then */
+ mode = AD7949_CFG_VAL_REF_INT_4096;
+ }
+ mode = AD7949_CFG_VAL_REF_EXT_TEMP;
}
+ mode = AD7949_CFG_VAL_REF_EXT_TEMP_BUF;

- ret = regulator_enable(ad7949_adc->vref);
- if (ret < 0) {
- dev_err(dev, "fail to enable regulator\n");
- return ret;
+ if (mode & AD7949_CFG_VAL_REF_EXTERNAL) {
+ ret = regulator_enable(ad7949_adc->vref);
+ if (ret < 0) {
+ dev_err(dev, "fail to enable regulator\n");
+ return ret;
+ }
+
+ ret = devm_add_action_or_reset(dev, ad7949_disable_reg,
+ ad7949_adc->vref);
+ if (ret)
+ return ret;
+ }
+
+ ad7949_adc->channels = devm_kcalloc(dev, spec->num_channels,
+ sizeof(*ad7949_adc->channels),
+ GFP_KERNEL);
+ if (!ad7949_adc->channels) {
+ dev_err(dev, "unable to allocate ADC channels\n");
+ return -ENOMEM;
+ }
+
+ /* Initialize all channel structures */
+ for (i = 0; i < spec->num_channels; i++)
+ ad7949_adc->channels[i].refsel = mode;
+
+ /* Read channel specific information form the devicetree */
+ device_for_each_child_node(dev, child) {
+ ret = fwnode_property_read_u32(child, "reg", &i);
+ if (ret) {
+ dev_err(dev, "missing reg property in %pfw\n", child);
+ fwnode_handle_put(child);
+ return ret;
+ }
+
+ ad7949_chan = &ad7949_adc->channels[i];
+
+ ret = fwnode_property_read_u32(child, "adi,internal-ref-microvolt", &tmp);
+ if (ret < 0 && ret != -EINVAL) {
+ dev_err(dev, "invalid internal reference in %pfw\n", child);
+ fwnode_handle_put(child);
+ return ret;
+ }
+
+ switch (tmp) {
+ case 2500000:
+ ad7949_chan->refsel = AD7949_CFG_VAL_REF_INT_2500;
+ break;
+ case 4096000:
+ ad7949_chan->refsel = AD7949_CFG_VAL_REF_INT_4096;
+ break;
+ default:
+ dev_err(dev, "unsupported internal voltage reference\n");
+ fwnode_handle_put(child);
+ return -EINVAL;
+ }
}

mutex_init(&ad7949_adc->lock);
@@ -367,7 +465,6 @@ static int ad7949_spi_probe(struct spi_device *spi)

err:
mutex_destroy(&ad7949_adc->lock);
- regulator_disable(ad7949_adc->vref);

return ret;
}
@@ -379,7 +476,6 @@ static int ad7949_spi_remove(struct spi_device *spi)

iio_device_unregister(indio_dev);
mutex_destroy(&ad7949_adc->lock);
- regulator_disable(ad7949_adc->vref);

return 0;
}
--
2.30.1.489.g328c10930387