Re: [PATCH RESEND v3 11/17] iio: adc: ad7768-1: add regulator to control VCM output

[David Lechner <dlechner@baylibre.com>]

On 2/12/25 12:17 PM, Jonathan Santos wrote:
> 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.
> 
> Signed-off-by: Jonathan Santos <Jonathan.Santos@analog.com>
> ---
> 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/ad7768-1.c | 138 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 138 insertions(+)
> 
> diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
> index 378245bce199..a359cd8fceca 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>
>  
> @@ -80,9 +82,15 @@
>  #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_RD_FLAG_MSK(x)		(BIT(6) | ((x) & 0x3F))
>  #define AD7768_WR_FLAG_MSK(x)		((x) & 0x3F)
>  
> +#define AD7768_VCM_OFF			0x08
> +
>  enum ad7768_conv_mode {
>  	AD7768_CONTINUOUS,
>  	AD7768_ONE_SHOT,
> @@ -160,6 +168,7 @@ struct ad7768_state {
>  	struct regmap *regmap;
>  	struct regmap *regmap24;
>  	struct regulator *vref;
> +	struct regulator_dev *vcm_rdev;
>  	struct clk *mclk;
>  	unsigned int mclk_freq;
>  	unsigned int samp_freq;
> @@ -643,6 +652,130 @@ static int ad7768_triggered_buffer_alloc(struct iio_dev *indio_dev)
>  					       &ad7768_buffer_ops);
>  }
>  
> +static int ad7768_vcm_enable(struct regulator_dev *rdev)
> +{
> +	struct ad7768_state *st = rdev_get_drvdata(rdev);
> +	int ret, val;
> +
> +	if (!st)
> +		return -EINVAL;

Do we need iio_device_claim_direct_mode() here to prevent accessing
registers on the ADC during a buffered read?

Same applies to other functions too.

> +
> +	ret = regmap_read(st->regmap, AD7768_REG_ANALOG2, &val);
> +	if (ret)
> +		return ret;
> +
> +	/* if regulator is off, turn it on */
> +	if (FIELD_GET(AD7768_REG_ANALOG2_VCM_MSK, val) == AD7768_VCM_OFF)

regmap_update_bits() already does this sort of check internally, so
open-coding it here is redundant.

> +		return regmap_update_bits(st->regmap, AD7768_REG_ANALOG2,
> +					  AD7768_REG_ANALOG2_VCM_MSK, 0x00);

Can be simplified with regmap_clear_bits().

> +
> +	return 0;
> +}
> +
> +static int ad7768_vcm_disable(struct regulator_dev *rdev)
> +{
> +	struct ad7768_state *st = rdev_get_drvdata(rdev);
> +
> +	if (!st)
> +		return -EINVAL;
> +
> +	return regmap_update_bits(st->regmap, AD7768_REG_ANALOG2,
> +				  AD7768_REG_ANALOG2_VCM_MSK, AD7768_VCM_OFF);
> +}
> +
> +static int ad7768_vcm_is_enabled(struct regulator_dev *rdev)
> +{
> +	struct ad7768_state *st = rdev_get_drvdata(rdev);
> +	int ret, val;
> +
> +	if (!st)
> +		return -EINVAL;
> +
> +	ret = regmap_read(st->regmap, AD7768_REG_ANALOG2, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (FIELD_GET(AD7768_REG_ANALOG2_VCM_MSK, val) == AD7768_VCM_OFF)
> +		return 0;

Could skip the if and just return directly.

> +
> +	return 1;
> +}
> +
> +static int ad7768_set_voltage_sel(struct regulator_dev *rdev,
> +				  unsigned int selector)
> +{
> +	unsigned int regval = AD7768_REG_ANALOG2_VCM(selector + 1);
> +	struct ad7768_state *st = rdev_get_drvdata(rdev);
> +
> +	if (!st)
> +		return -EINVAL;
> +
> +	return regmap_update_bits(st->regmap, AD7768_REG_ANALOG2,
> +				  AD7768_REG_ANALOG2_VCM_MSK, regval);
> +}
> +
> +static int ad7768_get_voltage_sel(struct regulator_dev *rdev)
> +{
> +	struct ad7768_state *st = rdev_get_drvdata(rdev);
> +	int ret, val;
> +
> +	if (!st)
> +		return -EINVAL;
> +
> +	ret = regmap_read(st->regmap, AD7768_REG_ANALOG2, &val);
> +	if (ret)
> +		return ret;
> +
> +	val = FIELD_GET(AD7768_REG_ANALOG2_VCM_MSK, val) - 1;
> +	val = clamp(val, 0, 8);
> +
> +	return val;
> +}
> +
> +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 = "vcm_output",

It looks like this is typically a datasheet name, like

"AD7768-1 VCM"

> +	.of_match = of_match_ptr("vcm_output"),

"vcm-output" as in DT bindings review.

> +	.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 regulator_config config = {
> +		.dev = dev,
> +		.driver_data = st,
> +	};
> +
> +	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;
> @@ -707,6 +840,11 @@ 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);
> +	if (ret)
> +		return ret;
> +
>  	ret = ad7768_setup(st);
>  	if (ret < 0) {
>  		dev_err(&spi->dev, "AD7768 setup failed\n");