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Date:   Fri, 09 Jul 2021 10:49:12 -0400
Message-Id: <CCOOXXRLLCT3.1HI9ZOJ2UT9W1@shaak>
Subject: RE: [PATCH v1 3/4] iio: adc: ad7949: add support for internal vref
From:   "Liam Beguin" <liambeguin@gmail.com>
To:     "Sa, Nuno" <Nuno.Sa@analog.com>,
        "lars@metafoo.de" <lars@metafoo.de>,
        "Hennerich, Michael" <Michael.Hennerich@analog.com>,
        "jic23@kernel.org" <jic23@kernel.org>,
        "charles-antoine.couret@essensium.com" 
        <charles-antoine.couret@essensium.com>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "robh+dt@kernel.org" <robh+dt@kernel.org>
References: <20210708235618.1541335-1-liambeguin@gmail.com>
 <20210708235618.1541335-4-liambeguin@gmail.com>
 <PH0PR03MB636680DD9F9530464FEBB7C399189@PH0PR03MB6366.namprd03.prod.outlook.com>
In-Reply-To: <PH0PR03MB636680DD9F9530464FEBB7C399189@PH0PR03MB6366.namprd03.prod.outlook.com>
Precedence: bulk

On Fri Jul 9, 2021 at 4:23 AM EDT, Sa, Nuno wrote:
> > From: Liam Beguin <liambeguin@gmail.com>
> > Sent: Friday, July 9, 2021 1:56 AM
> > To: liambeguin@gmail.com; lars@metafoo.de; Hennerich, Michael
> > <Michael.Hennerich@analog.com>; jic23@kernel.org; charles-
> > antoine.couret@essensium.com
> > Cc: linux-kernel@vger.kernel.org; linux-iio@vger.kernel.org;
> > devicetree@vger.kernel.org; robh+dt@kernel.org
> > Subject: [PATCH v1 3/4] iio: adc: ad7949: add support for internal vref
> >=20
> > [External]
> >=20
> > From: Liam Beguin <lvb@xiphos.com>
> >=20
> > 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.
> >=20
> > Signed-off-by: Liam Beguin <lvb@xiphos.com>
> > ---
> >  drivers/iio/adc/ad7949.c | 84
> > +++++++++++++++++++++++++++++++++-------
> >  1 file changed, 69 insertions(+), 15 deletions(-)
> >=20
> > diff --git a/drivers/iio/adc/ad7949.c b/drivers/iio/adc/ad7949.c
> > index bbc6b56330a3..3c1293922d2e 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)
> >=20
> > @@ -40,6 +41,33 @@ enum {
> >  	ID_AD7689,
> >  };
> >=20
> > +/**
> > + * enum ad7949_ref - Reference selection
> > + *
> > + * AD7949_REF_INT_2500:     Internal reference and temperature
> > sensor enabled.
> > + *                          Vref=3D2.5V, buffered output
> > + * AD7949_REF_INT_4096:     Internal reference and temperature
> > sensor enabled.
> > + *                          Vref=3D4.096V, 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 an=
d
> > + *                          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 =3D 0,
> > +	AD7949_REF_INT_4096,
> > +	AD7949_REF_EXT_TEMP,
> > +	AD7949_REF_EXT_TEMP_BUF,
> > +	AD7949_REF_EXT =3D 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[] =3D {
> >   * 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[] =3D {
> >  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;
> > @@ -241,12 +271,28 @@ static int ad7949_spi_read_raw(struct iio_dev
> > *indio_dev,
> >  		return IIO_VAL_INT;
> >=20
> >  	case IIO_CHAN_INFO_SCALE:
> > -		ret =3D regulator_get_voltage(ad7949_adc->vref);
> > -		if (ret < 0)
> > -			return ret;
> > +		switch (ad7949_adc->refsel) {
> > +		case AD7949_REF_INT_2500:
> > +			*val =3D 2500;
> > +			break;
> > +		case AD7949_REF_INT_4096:
> > +			*val =3D 4096;
> > +			break;
> > +		case AD7949_REF_EXT_TEMP:
> > +		case AD7949_REF_EXT_TEMP_BUF:
> > +		case AD7949_REF_EXT:
> > +		case AD7949_REF_EXT_BUF:
> > +			ret =3D regulator_get_voltage(ad7949_adc-
> > >vref);
> > +			if (ret < 0)
> > +				return ret;
> > +
> > +			/* convert value back to mV */
> > +			*val =3D ret / 1000;
> > +			break;
> > +		}
> >=20
> > -		*val =3D ret / 5000;
> > -		return IIO_VAL_INT;
> > +		*val2 =3D (1 << ad7949_adc->resolution) - 1;
> > +		return IIO_VAL_FRACTIONAL;
> >  	}
> >=20
> >  	return -EINVAL;
> > @@ -285,7 +331,7 @@ 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);
> >=20
> > @@ -304,6 +350,7 @@ static int ad7949_spi_init(struct
> > ad7949_adc_chip *ad7949_adc)
> >  static int ad7949_spi_probe(struct spi_device *spi)
> >  {
> >  	struct device *dev =3D &spi->dev;
> > +	struct device_node *np =3D dev->of_node;
> >  	const struct ad7949_adc_spec *spec;
> >  	struct ad7949_adc_chip *ad7949_adc;
> >  	struct iio_dev *indio_dev;
> > @@ -315,6 +362,7 @@ static int ad7949_spi_probe(struct spi_device
> > *spi)
> >  		return -ENOMEM;
> >  	}
> >=20
> > +	indio_dev->dev.of_node =3D np;
>
> Why doing this? The IIO core will do it for us at register time.

Sorry about that, will drop.

>
> >  	indio_dev->info =3D &ad7949_spi_info;
> >  	indio_dev->name =3D spi_get_device_id(spi)->name;
> >  	indio_dev->modes =3D INDIO_DIRECT_MODE;
> > @@ -330,16 +378,22 @@ static int ad7949_spi_probe(struct spi_device
> > *spi)
> >  	ad7949_adc->resolution =3D spec->resolution;
> >  	ad7949_set_bits_per_word(ad7949_adc);
> >=20
> > -	ad7949_adc->vref =3D 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 =3D AD7949_REF_EXT_BUF;
> > +	of_property_read_u32(np, "adi,reference-select",
> > &ad7949_adc->refsel);
>
> In case the property is given, we should make sure we get a valid
> value and error out if not...
>

I thought it would be handled later on when processing the sample, but
it's not really and it's better to fail early. I'll add that to v2.

Thanks,
Liam

> - Nuno S=C3=A1
> > -	ret =3D 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 =3D 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 =3D regulator_enable(ad7949_adc->vref);
> > +		if (ret < 0) {
> > +			dev_err(dev, "fail to enable regulator\n");
> > +			return ret;
> > +		}
> >  	}
> >=20
> >  	mutex_init(&ad7949_adc->lock);
> > --
> > 2.30.1.489.g328c10930387