linux-kernel - Re: [PATCH v3 08/13] iio: adc: ad7091r: Enable internal vref if external vref is not supplied

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Message-ID: <20231210122218.6c0c1d19@jic23-huawei>
Date:   Sun, 10 Dec 2023 12:22:18 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Marcelo Schmitt <marcelo.schmitt@...log.com>
Cc:     <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>,
        <marcelo.schmitt1@...il.com>, <linux-iio@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 08/13] iio: adc: ad7091r: Enable internal vref if
 external vref is not supplied

On Thu, 7 Dec 2023 15:41:25 -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>
> ---
>  drivers/iio/adc/ad7091r-base.c | 9 ++++++---
>  drivers/iio/adc/ad7091r-base.h | 1 +
>  2 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad7091r-base.c b/drivers/iio/adc/ad7091r-base.c
> index f2cb638b8d77..59a7ec44955d 100644
> --- a/drivers/iio/adc/ad7091r-base.c
> +++ b/drivers/iio/adc/ad7091r-base.c
> @@ -215,10 +215,13 @@ int ad7091r_probe(struct device *dev, const char *name,
>  	iio_dev->channels = st->chip_info->channels;
>  
>  	st->vref = devm_regulator_get_optional(dev, "vref");

This does not return NULL, only a valid regulator or an error code.

> -	if (IS_ERR(st->vref)) {
> -		if (PTR_ERR(st->vref) == -EPROBE_DEFER)
> -			return -EPROBE_DEFER;
> +	if (IS_ERR_OR_NULL(st->vref)) {

You still need to explicitly handle deferal here.
There might be a perfectly good regulator that just isn't ready yet and
if that happens we want to try probing this driver again later rather
than papering over it.


> +		/* Enable internal vref */
>  		st->vref = NULL;
> +		ret = regmap_update_bits(st->map, AD7091R_REG_CONF,
> +					 AD7091R_REG_CONF_INT_VREF, BIT(0));
> +		if (ret)
> +			return ret;
>  	} 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 9546d0bf1da7..e153c2d7deb5 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)