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Message-ID: <2bc93cdf-e6d0-4879-a637-04db0bfe45aa@baylibre.com>
Date: Thu, 20 Feb 2025 16:20:51 -0600
From: David Lechner <dlechner@...libre.com>
To: Jonathan Santos <Jonathan.Santos@...log.com>, linux-iio@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: lars@...afoo.de, Michael.Hennerich@...log.com,
marcelo.schmitt@...log.com, jic23@...nel.org, robh@...nel.org,
krzk+dt@...nel.org, conor+dt@...nel.org, jonath4nns@...il.com,
marcelo.schmitt1@...il.com
Subject: Re: [PATCH RESEND v3 11/17] iio: adc: ad7768-1: add regulator to
control VCM output
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@...log.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");
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