Re: [PATCH v3 2/4] iio: adc: ad799x: cache regulator voltages during probe

[David Lechner <dlechner@baylibre.com>]

On 3/2/26 7:06 AM, Archit Anant wrote:
> Reading the regulator voltage via regulator_get_voltage() can be a slow
> operation. Since the reference voltages for this ADC are not expected to
> change at runtime, it is inefficient to query the regulator API every
> time userspace reads the IIO_CHAN_INFO_SCALE attribute.
> 
> Cache the VCC and VREF voltages in the state structure during probe().
> This improves the performance of ad799x_read_raw() and removes the
> dependency on the regulator pointers during fast-path reads.
> 
> Suggested-by: Jonathan Cameron <jic23@kernel.org>
> Signed-off-by: Archit Anant <architanant5@gmail.com>
> ---
>  drivers/iio/adc/ad799x.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad799x.c b/drivers/iio/adc/ad799x.c
> index 7775be874081..35e0589428d0 100644
> --- a/drivers/iio/adc/ad799x.c
> +++ b/drivers/iio/adc/ad799x.c
> @@ -135,6 +135,10 @@ struct ad799x_state {
>  	u16				config;
>  
>  	unsigned int			transfer_size;
> +
> +	int				vcc_uv;
> +	int				vref_uv;
> +
>  	IIO_DECLARE_DMA_BUFFER_WITH_TS(__be16, rx_buf, AD799X_MAX_CHANNELS);
>  };
>  
> @@ -303,9 +307,9 @@ static int ad799x_read_raw(struct iio_dev *indio_dev,
>  		return IIO_VAL_INT;
>  	case IIO_CHAN_INFO_SCALE:
>  		if (st->vref)
> -			ret = regulator_get_voltage(st->vref);
> +			ret = st->vref_uv;
>  		else
> -			ret = regulator_get_voltage(st->reg);
> +			ret = st->vcc_uv;
>  
>  		if (ret < 0)
>  			return ret;

This can be simplified even more. See reply to v2.

We could even move the if statement to probe and only
add one state variable.