[PATCH v5 08/14] iio: adc: ad7768-1: add regulator to control VCM output

Jonathan Santos
2025-04-11T15:58:18Z

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 using the regulator
framework.

Acked-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
---
v5 Changes:
* enforce AD7768_REG_ANALOG2_VCM macro argument evaluation.
* switched to the new iio_device_claim/release_direct() functions.

v4 Changes:
* Added iio_device_claim_direct_mode() to regulator callbacks to avoid register access
while in buffered mode.
* Changed regulator name to "ad7768-1-vcm".
* When regulator enable is called, it will set the last voltage selector configured.
* Disabled regulator before configuring it.
* Adressed other nits.

v3 Changes:
* Register VCM output via the regulator framework for improved flexibility
and external integration.

v2 Changes:
* VCM output support is now defined by a devicetree property, instead of
and IIO attribute.
---
drivers/iio/adc/Kconfig | 1 +
drivers/iio/adc/ad7768-1.c | 176 +++++++++++++++++++++++++++++++++++++
2 files changed, 177 insertions(+)

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index da3463a1d0bc..f1600a0fa5f2 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -322,6 +322,7 @@ config AD7766
config AD7768_1
tristate "Analog Devices AD7768-1 ADC driver"
depends on SPI
+ select REGULATOR
select REGMAP_SPI
select IIO_BUFFER
select IIO_TRIGGER
diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
index 66087fabe181..13d17a13b6ea 100644
--- a/drivers/iio/adc/ad7768-1.c
+++ b/drivers/iio/adc/ad7768-1.c
@@ -12,8 +12,10 @@
#include <linux/gpio/consumer.h>
#include <linux/kernel.h>
#include <linux/module.h>
+#include <linux/of.h>
#include <linux/regmap.h>
#include <linux/regulator/consumer.h>
+#include <linux/regulator/driver.h>
#include <linux/sysfs.h>
#include <linux/spi/spi.h>

@@ -80,6 +82,12 @@
#define AD7768_CONV_MODE_MSK GENMASK(2, 0)
#define AD7768_CONV_MODE(x) FIELD_PREP(AD7768_CONV_MODE_MSK, x)

+/* AD7768_REG_ANALOG2 */
+#define AD7768_REG_ANALOG2_VCM_MSK GENMASK(2, 0)
+#define AD7768_REG_ANALOG2_VCM(x) FIELD_PREP(AD7768_REG_ANALOG2_VCM_MSK, (x))
+
+#define AD7768_VCM_OFF 0x07
+
enum ad7768_conv_mode {
AD7768_CONTINUOUS,
AD7768_ONE_SHOT,
@@ -157,6 +165,8 @@ struct ad7768_state {
struct regmap *regmap;
struct regmap *regmap24;
struct regulator *vref;
+ struct regulator_dev *vcm_rdev;
+ unsigned int vcm_output_sel;
struct clk *mclk;
unsigned int mclk_freq;
unsigned int samp_freq;
@@ -644,6 +654,167 @@ static int ad7768_triggered_buffer_alloc(struct iio_dev *indio_dev)
&ad7768_buffer_ops);
}

+static int ad7768_vcm_enable(struct regulator_dev *rdev)
+{
+ struct iio_dev *indio_dev = rdev_get_drvdata(rdev);
+ struct ad7768_state *st = iio_priv(indio_dev);
+ int ret, regval;
+
+ if (!indio_dev)
+ return -EINVAL;
+
+ if (!iio_device_claim_direct(indio_dev))
+ return -EBUSY;
+
+ /* To enable, set the last selected output */
+ regval = AD7768_REG_ANALOG2_VCM(st->vcm_output_sel + 1);
+ ret = regmap_update_bits(st->regmap, AD7768_REG_ANALOG2,
+ AD7768_REG_ANALOG2_VCM_MSK, regval);
+ iio_device_release_direct(indio_dev);
+
+ return ret;
+}
+
+static int ad7768_vcm_disable(struct regulator_dev *rdev)
+{
+ struct iio_dev *indio_dev = rdev_get_drvdata(rdev);
+ struct ad7768_state *st = iio_priv(indio_dev);
+ int ret;
+
+ if (!indio_dev)
+ return -EINVAL;
+
+ if (!iio_device_claim_direct(indio_dev))
+ return -EBUSY;
+
+ ret = regmap_update_bits(st->regmap, AD7768_REG_ANALOG2,
+ AD7768_REG_ANALOG2_VCM_MSK, AD7768_VCM_OFF);
+ iio_device_release_direct(indio_dev);
+
+ return ret;
+}
+
+static int ad7768_vcm_is_enabled(struct regulator_dev *rdev)
+{
+ struct iio_dev *indio_dev = rdev_get_drvdata(rdev);
+ struct ad7768_state *st = iio_priv(indio_dev);
+ int ret, val;
+
+ if (!indio_dev)
+ return -EINVAL;
+
+ if (!iio_device_claim_direct(indio_dev))
+ return -EBUSY;
+
+ ret = regmap_read(st->regmap, AD7768_REG_ANALOG2, &val);
+ if (ret)
+ goto err_release;
+
+ ret = FIELD_GET(AD7768_REG_ANALOG2_VCM_MSK, val) != AD7768_VCM_OFF;
+err_release:
+ iio_device_release_direct(indio_dev);
+
+ return ret;
+}
+
+static int ad7768_set_voltage_sel(struct regulator_dev *rdev,
+ unsigned int selector)
+{
+ unsigned int regval = AD7768_REG_ANALOG2_VCM(selector + 1);
+ struct iio_dev *indio_dev = rdev_get_drvdata(rdev);
+ struct ad7768_state *st = iio_priv(indio_dev);
+ int ret;
+
+ if (!indio_dev)
+ return -EINVAL;
+
+ if (!iio_device_claim_direct(indio_dev))
+ return -EBUSY;
+
+ ret = regmap_update_bits(st->regmap, AD7768_REG_ANALOG2,
+ AD7768_REG_ANALOG2_VCM_MSK, regval);
+ iio_device_release_direct(indio_dev);
+ st->vcm_output_sel = selector;
+
+ return ret;
+}
+
+static int ad7768_get_voltage_sel(struct regulator_dev *rdev)
+{
+ struct iio_dev *indio_dev = rdev_get_drvdata(rdev);
+ struct ad7768_state *st = iio_priv(indio_dev);
+ int ret, val;
+
+ if (!indio_dev)
+ return -EINVAL;
+
+ if (!iio_device_claim_direct(indio_dev))
+ return -EBUSY;
+
+ ret = regmap_read(st->regmap, AD7768_REG_ANALOG2, &val);
+ if (ret)
+ goto err_release;
+
+ val = FIELD_GET(AD7768_REG_ANALOG2_VCM_MSK, val);
+ ret = clamp(val, 1, (int)rdev->desc->n_voltages) - 1;
+err_release:
+ iio_device_release_direct(indio_dev);
+
+ return ret;
+}
+
+static const struct regulator_ops vcm_regulator_ops = {
+ .enable = ad7768_vcm_enable,
+ .disable = ad7768_vcm_disable,
+ .is_enabled = ad7768_vcm_is_enabled,
+ .list_voltage = regulator_list_voltage_table,
+ .set_voltage_sel = ad7768_set_voltage_sel,
+ .get_voltage_sel = ad7768_get_voltage_sel,
+};
+
+static const unsigned int vcm_voltage_table[] = {
+ 2500000,
+ 2050000,
+ 1650000,
+ 1900000,
+ 1100000,
+ 900000,
+};
+
+static const struct regulator_desc vcm_desc = {
+ .name = "ad7768-1-vcm",
+ .of_match = of_match_ptr("vcm-output"),
+ .regulators_node = of_match_ptr("regulators"),
+ .n_voltages = ARRAY_SIZE(vcm_voltage_table),
+ .volt_table = vcm_voltage_table,
+ .ops = &vcm_regulator_ops,
+ .type = REGULATOR_VOLTAGE,
+ .owner = THIS_MODULE,
+};
+
+static int ad7768_register_regulators(struct device *dev, struct ad7768_state *st,
+ struct iio_dev *indio_dev)
+{
+ struct regulator_config config = {
+ .dev = dev,
+ .driver_data = indio_dev,
+ };
+ int ret;
+
+ /* Disable the regulator before registering it */
+ ret = regmap_update_bits(st->regmap, AD7768_REG_ANALOG2,
+ AD7768_REG_ANALOG2_VCM_MSK, AD7768_VCM_OFF);
+ if (ret)
+ return -EINVAL;
+
+ st->vcm_rdev = devm_regulator_register(dev, &vcm_desc, &config);
+ if (IS_ERR(st->vcm_rdev))
+ return dev_err_probe(dev, PTR_ERR(st->vcm_rdev),
+ "failed to register VCM regulator\n");
+
+ return 0;
+}
+
static int ad7768_probe(struct spi_device *spi)
{
struct ad7768_state *st;
@@ -708,6 +879,11 @@ static int ad7768_probe(struct spi_device *spi)
indio_dev->info = &ad7768_info;
indio_dev->modes = INDIO_DIRECT_MODE;

+ /* Register VCM output regulator */
+ ret = ad7768_register_regulators(&spi->dev, st, indio_dev);
+ if (ret)
+ return ret;
+
ret = ad7768_setup(st);
if (ret < 0) {
dev_err(&spi->dev, "AD7768 setup failed\n");
--
2.34.1