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SubjectRe: [PATCH v2 3/4] iio: adc: ad7949: add support for internal vref
On Fri,  9 Jul 2021 11:58:55 -0400
Liam Beguin <liambeguin@gmail.com> wrote:

> 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 | 94 ++++++++++++++++++++++++++++++++++------
> 1 file changed, 80 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> index 770112ac820f..a20fd81a0830 100644
> --- a/drivers/iio/adc/ad7949.c
> +++ b/drivers/iio/adc/ad7949.c
> @@ -31,6 +31,7 @@
> #define AD7949_CFG_VAL_BW_FULL 1
> #define AD7949_CFG_VAL_BW_QUARTER 0
> #define AD7949_CFG_BIT_REF GENMASK(5, 3)
> +#define AD7949_CFG_VAL_REF_EXTERNAL BIT(1)
> #define AD7949_CFG_BIT_SEQ GENMASK(2, 1)
> #define AD7949_CFG_BIT_RBN BIT(0)
>
> @@ -40,6 +41,33 @@ enum {
> ID_AD7689,
> };
>
> +/**
> + * enum ad7949_ref - Reference selection
> + *
> + * AD7949_REF_INT_2500: Internal reference and temperature sensor enabled.
> + * Vref=2.5V, buffered output
> + * AD7949_REF_INT_4096: Internal reference and temperature sensor enabled.
> + * Vref=4.096V, buffered output
> + * AD7949_REF_EXT_TEMP: Use external reference, temperature sensor enabled.
> + * Internal buffer disabled
> + * AD7949_REF_EXT_TEMP_BUF: Use external reference, internal buffer and
> + * temperature sensor enabled.
> + * AD7949_REF_RSRV_4: Do not use
> + * AD7949_REF_RSRV_5: Do not use
> + * AD7949_REF_EXT: Use external reference, internal buffer and
> + * temperature sensor disabled.
> + * AD7949_REF_EXT_BUF: Use external reference, internal buffer enabled.
> + * Internal reference and temperature sensor disabled.
> + */
> +enum ad7949_ref {
> + AD7949_REF_INT_2500 = 0,

For case where you have gaps like this, an ENUM is probably not appropriate.
I'd just used defines.

> + AD7949_REF_INT_4096,
> + AD7949_REF_EXT_TEMP,
> + AD7949_REF_EXT_TEMP_BUF,
> + AD7949_REF_EXT = 6,
> + AD7949_REF_EXT_BUF,
> +};
> +
> struct ad7949_adc_spec {
> u8 num_channels;
> u8 resolution;
> @@ -55,6 +83,7 @@ static const struct ad7949_adc_spec ad7949_adc_spec[] = {
> * struct ad7949_adc_chip - AD ADC chip
> * @lock: protects write sequences
> * @vref: regulator generating Vref
> + * @refsel: reference selection
> * @indio_dev: reference to iio structure
> * @spi: reference to spi structure
> * @resolution: resolution of the chip
> @@ -66,6 +95,7 @@ static const struct ad7949_adc_spec ad7949_adc_spec[] = {
> struct ad7949_adc_chip {
> struct mutex lock;
> struct regulator *vref;
> + enum ad7949_ref refsel;
> struct iio_dev *indio_dev;
> struct spi_device *spi;
> u8 resolution;
> @@ -243,12 +273,28 @@ 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_adc->refsel) {
> + case AD7949_REF_INT_2500:
> + *val = 2500;
> + break;
> + case AD7949_REF_INT_4096:
> + *val = 4096;
> + break;
> + case AD7949_REF_EXT_TEMP:
> + case AD7949_REF_EXT_TEMP_BUF:
> + case AD7949_REF_EXT:
> + case AD7949_REF_EXT_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;
> @@ -287,7 +333,7 @@ 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, AD7949_CFG_VAL_BW_FULL) |
> - FIELD_PREP(AD7949_CFG_BIT_REF, AD7949_REF_EXT_BUF) |
> + FIELD_PREP(AD7949_CFG_BIT_REF, ad7949_adc->refsel) |
> FIELD_PREP(AD7949_CFG_BIT_SEQ, 0x0) |
> FIELD_PREP(AD7949_CFG_BIT_RBN, 1);
>
> @@ -306,6 +352,7 @@ static int ad7949_spi_init(struct ad7949_adc_chip *ad7949_adc)
> static int ad7949_spi_probe(struct spi_device *spi)
> {
> struct device *dev = &spi->dev;
> + struct device_node *np = dev->of_node;
> const struct ad7949_adc_spec *spec;
> struct ad7949_adc_chip *ad7949_adc;
> struct iio_dev *indio_dev;
> @@ -332,16 +379,35 @@ static int ad7949_spi_probe(struct spi_device *spi)
> ad7949_adc->resolution = spec->resolution;
> ad7949_set_bits_per_word(ad7949_adc);
>
> - ad7949_adc->vref = devm_regulator_get(dev, "vref");
> - if (IS_ERR(ad7949_adc->vref)) {
> - dev_err(dev, "fail to request regulator\n");
> - return PTR_ERR(ad7949_adc->vref);
> + /* Set default devicetree parameters */
> + ad7949_adc->refsel = AD7949_REF_EXT_BUF;
> + of_property_read_u32(np, "adi,reference-select", &ad7949_adc->refsel);

Check for errors. Not being present is fine, but other errors may not be.


> + switch (ad7949_adc->refsel) {
> + case AD7949_REF_INT_2500:
> + case AD7949_REF_INT_4096:
> + case AD7949_REF_EXT_TEMP:
> + case AD7949_REF_EXT_TEMP_BUF:
> + case AD7949_REF_EXT:
> + case AD7949_REF_EXT_BUF:
> + break;
> + default:
> + dev_err(dev, "invalid adi,reference-select value (%d)\n",
> + ad7949_adc->refsel);
> + return -EINVAL;
> }
>
> - ret = regulator_enable(ad7949_adc->vref);
> - if (ret < 0) {
> - dev_err(dev, "fail to enable regulator\n");
> - return ret;
> + if (ad7949_adc->refsel & AD7949_CFG_VAL_REF_EXTERNAL) {
> + ad7949_adc->vref = devm_regulator_get(dev, "vref");
> + if (IS_ERR(ad7949_adc->vref)) {
> + dev_err(dev, "fail to request regulator\n");
> + return PTR_ERR(ad7949_adc->vref);
> + }
> +
> + ret = regulator_enable(ad7949_adc->vref);

Shouldn't be calling regulator_disable unless you enabled it...

> + if (ret < 0) {
> + dev_err(dev, "fail to enable regulator\n");
> + return ret;
> + }
> }
>
> mutex_init(&ad7949_adc->lock);

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