linux-kernel - Re: [PATCH v4 09/15] iio: adc: ad7091r: Enable internal vref if external vref is not supplied

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Date: Mon, 18 Dec 2023 14:35:27 -0300
From: Marcelo Schmitt <marcelo.schmitt1@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Marcelo Schmitt <marcelo.schmitt@...log.com>, apw@...onical.com,
	joe@...ches.com, dwaipayanray1@...il.com, lukas.bulwahn@...il.com,
	paul.cercueil@...log.com, Michael.Hennerich@...log.com,
	lars@...afoo.de, robh+dt@...nel.org,
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
	dan.carpenter@...aro.org, dlechner@...libre.com,
	linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 09/15] iio: adc: ad7091r: Enable internal vref if
 external vref is not supplied

On 12/17, Jonathan Cameron wrote:
> On Sat, 16 Dec 2023 14:49:07 -0300
> Marcelo Schmitt <marcelo.schmitt@...log.com> wrote:
> 
> > The ADC needs a voltage reference to work correctly.
> > Enable AD7091R internal voltage reference if no external vref is supplied.
> > 
> > Signed-off-by: Marcelo Schmitt <marcelo.schmitt@...log.com>
> This one sounds to me like it should have a fixes tag and be
> much earlier in the set to perhaps simplify backports.

Could be. If we stick to the fact that the dt-binding does not require a voltage
regulator then this can be seen as a fix.
Though, if users can provide an external reference this patch makes no
difference them.
I am using the internal reference for testing so having this one makes a
difference for me.

> 
> Jonathan
> 
> > ---
> >  drivers/iio/adc/ad7091r-base.c | 7 +++++++
> >  drivers/iio/adc/ad7091r-base.h | 1 +
> >  2 files changed, 8 insertions(+)
> > 
> > diff --git a/drivers/iio/adc/ad7091r-base.c b/drivers/iio/adc/ad7091r-base.c
> > index aead72ef55b6..9d0b489966f5 100644
> > --- a/drivers/iio/adc/ad7091r-base.c
> > +++ b/drivers/iio/adc/ad7091r-base.c
> > @@ -217,7 +217,14 @@ int ad7091r_probe(struct device *dev, const struct ad7091r_init_info *init_info,
> >  	if (IS_ERR(st->vref)) {
> >  		if (PTR_ERR(st->vref) == -EPROBE_DEFER)
> >  			return -EPROBE_DEFER;
> > +
> >  		st->vref = NULL;
> > +		/* Enable internal vref */
> > +		ret = regmap_update_bits(st->map, AD7091R_REG_CONF,
> > +					 AD7091R_REG_CONF_INT_VREF, BIT(0));
> > +		if (ret)
> > +			return dev_err_probe(st->dev, ret,
> > +					     "Error on enable internal reference\n");
> >  	} else {
> >  		ret = regulator_enable(st->vref);
> >  		if (ret)
> > diff --git a/drivers/iio/adc/ad7091r-base.h b/drivers/iio/adc/ad7091r-base.h
> > index 81b8a4bbb929..9cfb362a00a4 100644
> > --- a/drivers/iio/adc/ad7091r-base.h
> > +++ b/drivers/iio/adc/ad7091r-base.h
> > @@ -20,6 +20,7 @@
> >  #define AD7091R_REG_CH_HYSTERESIS(ch) ((ch) * 3 + 6)
> >  
> >  /* AD7091R_REG_CONF */
> > +#define AD7091R_REG_CONF_INT_VREF	BIT(0)
> >  #define AD7091R_REG_CONF_ALERT_EN	BIT(4)
> >  #define AD7091R_REG_CONF_AUTO		BIT(8)
> >  #define AD7091R_REG_CONF_CMD		BIT(10)
> 
>