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

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Date: Mon, 3 Jun 2024 08:38:34 -0500
From: David Lechner <dlechner@...libre.com>
To: Jonathan Cameron <jic23@...nel.org>
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 6/1/24 8:01 AM, Jonathan Cameron wrote:
> 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...
> 

Hmm... don't remember why I did it that way (was a while ago). I will bring
back the have_refin flag instead.