[PATCH v2 11/16] iio: adc: ad7768-1: Add VCM output support

[Jonathan Santos]

From: Sergiu Cuciurean <sergiu.cuciurean@xxxxxxxxxx>

The VCM output voltage can be used as a common-mode voltage within the
amplifier preconditioning circuits external to the AD7768-1.

This change allows the user to configure VCM output trough a devicetree
attribute.

Co-developed-by: Jonathan Santos <Jonathan.Santos@xxxxxxxxxx>
Signed-off-by: Jonathan Santos <Jonathan.Santos@xxxxxxxxxx>
Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@xxxxxxxxxx>
---
v2 Changes:
* VCM output support is now defined by a devicetree property, instead of 
  and IIO attribute.
---
 drivers/iio/adc/ad7768-1.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
index 8487b9a06609..c540583808c2 100644
--- a/drivers/iio/adc/ad7768-1.c
+++ b/drivers/iio/adc/ad7768-1.c
@@ -24,6 +24,8 @@
 #include <linux/iio/triggered_buffer.h>
 #include <linux/iio/trigger_consumer.h>
 
+#include <dt-bindings/iio/adc/adi,ad7768-1.h>
+
 /* AD7768 registers definition */
 #define AD7768_REG_CHIP_TYPE		0x3
 #define AD7768_REG_PROD_ID_L		0x4
@@ -347,6 +349,11 @@ static int ad7768_set_freq(struct ad7768_state *st,
 	return 0;
 }
 
+static int ad7768_set_vcm_output(struct ad7768_state *st, unsigned int mode)
+{
+	return regmap_write(st->regmap, AD7768_REG_ANALOG2, mode);
+}
+
 static ssize_t ad7768_sampling_freq_avail(struct device *dev,
 					  struct device_attribute *attr,
 					  char *buf)
@@ -628,6 +635,7 @@ static int ad7768_probe(struct spi_device *spi)
 {
 	struct ad7768_state *st;
 	struct iio_dev *indio_dev;
+	u32 val;
 	int ret;
 
 	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
@@ -688,6 +696,18 @@ static int ad7768_probe(struct spi_device *spi)
 	indio_dev->info = &ad7768_info;
 	indio_dev->modes = INDIO_DIRECT_MODE;
 
+	ret = device_property_read_u32(&spi->dev, "adi,vcm-output", &val);
+	if (!ret) {
+		if (val > AD7768_VCM_OUTPUT_OFF) {
+			dev_err(&spi->dev, "Invalid VCM output value\n");
+			return -EINVAL;
+		}
+
+		ret = ad7768_set_vcm_output(st, val);
+		if (ret)
+			return ret;
+	}
+
 	ret = ad7768_setup(st);
 	if (ret < 0) {
 		dev_err(&spi->dev, "AD7768 setup failed\n");
-- 
2.34.1