linux-kernel - Re: [PATCH 5/5] iio: adc: ad7944: use devm_regulator_get_enable_read

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Date: Sat, 1 Jun 2024 14:01:39 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: David Lechner <dlechner@...libre.com>
Cc: Marcelo Schmitt <marcelo.schmitt1@...il.com>, Nuno Sá
 <nuno.sa@...log.com>, Michael Hennerich <Michael.Hennerich@...log.com>,
 Mark Brown <broonie@...nel.org>, Liam Girdwood <lgirdwood@...il.com>,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] iio: adc: ad7944: use
 devm_regulator_get_enable_read_voltage

On Fri, 31 May 2024 16:19:36 -0500
David Lechner <dlechner@...libre.com> wrote:

> This makes use of the new devm_regulator_get_enable_read_voltage()
> function to reduce boilerplate code.
> 
> Signed-off-by: David Lechner <dlechner@...libre.com>
A possible corner case inline.

Patches 2-4 lgtm.
> ---
>  drivers/iio/adc/ad7944.c | 62 +++++++++++++++---------------------------------
>  1 file changed, 19 insertions(+), 43 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad7944.c b/drivers/iio/adc/ad7944.c
> index e2cb64cef476..42bbcb904778 100644
> --- a/drivers/iio/adc/ad7944.c
> +++ b/drivers/iio/adc/ad7944.c
> @@ -464,23 +464,16 @@ static const char * const ad7944_power_supplies[] = {
>  	"avdd",	"dvdd",	"bvdd", "vio"
>  };
>  
> -static void ad7944_ref_disable(void *ref)
> -{
> -	regulator_disable(ref);
> -}
> -
>  static int ad7944_probe(struct spi_device *spi)
>  {
>  	const struct ad7944_chip_info *chip_info;
>  	struct device *dev = &spi->dev;
>  	struct iio_dev *indio_dev;
>  	struct ad7944_adc *adc;
> -	bool have_refin = false;
> -	struct regulator *ref;
>  	struct iio_chan_spec *chain_chan;
>  	unsigned long *chain_scan_masks;
>  	u32 n_chain_dev;
> -	int ret;
> +	int ret, ref_mv, refin_mv;
>  
>  	indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));
>  	if (!indio_dev)
> @@ -531,47 +524,30 @@ static int ad7944_probe(struct spi_device *spi)
>  	 * - external reference: REF is connected, REFIN is not connected
>  	 */
>  
> -	ref = devm_regulator_get_optional(dev, "ref");
> -	if (IS_ERR(ref)) {
> -		if (PTR_ERR(ref) != -ENODEV)
> -			return dev_err_probe(dev, PTR_ERR(ref),
> -					     "failed to get REF supply\n");
> -
> -		ref = NULL;
> -	}
> +	ret = devm_regulator_get_enable_read_voltage(dev, "ref");
> +	if (ret == -ENODEV)
> +		ref_mv = 0;
> +	else if (ret < 0)
> +		return dev_err_probe(dev, ret, "failed to get REF voltage\n");
> +	else
> +		ref_mv = ret / 1000;
>  
> -	ret = devm_regulator_get_enable_optional(dev, "refin");
> -	if (ret == 0)
> -		have_refin = true;
> -	else if (ret != -ENODEV)
> -		return dev_err_probe(dev, ret,
> -				     "failed to get and enable REFIN supply\n");
> +	ret = devm_regulator_get_enable_read_voltage(dev, "refin");
> +	if (ret == -ENODEV)
> +		refin_mv = 0;
> +	else if (ret < 0)
> +		return dev_err_probe(dev, ret, "failed to get REFIN voltage\n");
> +	else
> +		refin_mv = ret / 1000;
How does refin_mv get used?  Previously we never queried it's voltage (I assume
because it supplies an internal reference?

Are there any regulators that are real enough to enable but for which a voltage
can't be queried?  I think fixed regulators with gpio control are in this
category...

>  
> -	if (have_refin && ref)
> +	if (ref_mv && refin_mv)
>  		return dev_err_probe(dev, -EINVAL,
>  				     "cannot have both refin and ref supplies\n");
>  
> -	if (ref) {
> -		ret = regulator_enable(ref);
> -		if (ret)
> -			return dev_err_probe(dev, ret,
> -					     "failed to enable REF supply\n");
> -
> -		ret = devm_add_action_or_reset(dev, ad7944_ref_disable, ref);
> -		if (ret)
> -			return ret;
> -
> -		ret = regulator_get_voltage(ref);
> -		if (ret < 0)
> -			return dev_err_probe(dev, ret,
> -					     "failed to get REF voltage\n");
> -
> -		/* external reference */
> -		adc->ref_mv = ret / 1000;
> -	} else {
> -		/* internal reference */
> +	if (ref_mv)
> +		adc->ref_mv = ref_mv;
> +	else
>  		adc->ref_mv = AD7944_INTERNAL_REF_MV;
> -	}
>  
>  	adc->cnv = devm_gpiod_get_optional(dev, "cnv", GPIOD_OUT_LOW);
>  	if (IS_ERR(adc->cnv))
>