Re: [PATCH RFC 4/7] iio: addac: ad74115: Use devm_regulator_get_enable_get_voltage()

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 27 Mar 2024 18:18:53 -0500
David Lechner <dlechner@baylibre.com> wrote:

> We can reduce boilerplate code by using
> devm_regulator_get_enable_get_voltage().
There is a change in behaviour in this one. I'd like some
explanation in the patch title for why it is always safe to get
the voltage of avdd_mv when previously it wasn't.

There seems to me to be a corner case where a DTS is not providing
the entry because it's always powered on so we get a stub regulator
but that doesn't matter because we aren't in DIN_THRESHOLD_MOD_AVDD.
After this change that dts is broken as now we read the voltage
whatever.

You could use the optional form and then fail the probe if
in a mode where the value will be used?

> 
> Signed-off-by: David Lechner <dlechner@baylibre.com>
> ---
>  drivers/iio/addac/ad74115.c | 28 +++-------------------------
>  1 file changed, 3 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/iio/addac/ad74115.c b/drivers/iio/addac/ad74115.c
> index e6bc5eb3788d..01073d7de6aa 100644
> --- a/drivers/iio/addac/ad74115.c
> +++ b/drivers/iio/addac/ad74115.c
> @@ -199,7 +199,6 @@ struct ad74115_state {
>  	struct spi_device		*spi;
>  	struct regmap			*regmap;
>  	struct iio_trigger		*trig;
> -	struct regulator		*avdd;
>  
>  	/*
>  	 * Synchronize consecutive operations when doing a one-shot
> @@ -1672,14 +1671,6 @@ static int ad74115_setup(struct iio_dev *indio_dev)
>  	if (ret)
>  		return ret;
>  
> -	if (val == AD74115_DIN_THRESHOLD_MODE_AVDD) {
> -		ret = regulator_get_voltage(st->avdd);
> -		if (ret < 0)
> -			return ret;
> -
> -		st->avdd_mv = ret / 1000;
> -	}
> -
>  	st->din_threshold_mode = val;
>  
>  	ret = ad74115_apply_fw_prop(st, &ad74115_dac_bipolar_fw_prop, &val);
> @@ -1788,11 +1779,6 @@ static int ad74115_reset(struct ad74115_state *st)
>  	return 0;
>  }
>  
> -static void ad74115_regulator_disable(void *data)
> -{
> -	regulator_disable(data);
> -}
> -
>  static int ad74115_setup_trigger(struct iio_dev *indio_dev)
>  {
>  	struct ad74115_state *st = iio_priv(indio_dev);
> @@ -1855,19 +1841,11 @@ static int ad74115_probe(struct spi_device *spi)
>  	indio_dev->modes = INDIO_DIRECT_MODE;
>  	indio_dev->info = &ad74115_info;
>  
> -	st->avdd = devm_regulator_get(dev, "avdd");
> -	if (IS_ERR(st->avdd))
> -		return PTR_ERR(st->avdd);
> -
> -	ret = regulator_enable(st->avdd);
> -	if (ret) {
> -		dev_err(dev, "Failed to enable avdd regulator\n");
> +	ret = devm_regulator_get_enable_get_voltage(dev, "avdd");
> +	if (ret < 0)
>  		return ret;
> -	}
>  
> -	ret = devm_add_action_or_reset(dev, ad74115_regulator_disable, st->avdd);
> -	if (ret)
> -		return ret;
> +	st->avdd_mv = ret / 1000;
>  
>  	ret = devm_regulator_bulk_get_enable(dev, ARRAY_SIZE(regulator_names),
>  					     regulator_names);
>