Re: [PATCH v2] iio: adc: axp20x_adc: fix charging current reporting on AXP22x

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 17 Nov 2021 00:37:46 +0300
Evgeny Boger <boger@wirenboard.com> wrote:

> Both the charging and discharging currents on AXP22x are stored as
> 12-bit integers, in accordance with the datasheet.
> It's also confirmed by vendor BSP (axp20x_adc.c:axp22_icharge_to_mA).
> 
> The scale factor of 0.5 is never mentioned in datasheet, nor in the
> vendor source code. I think it was here to compensate for
> erroneous addition bit in register width.
> 
> Tested on custom A40i+AXP221s board with external ammeter as
> a reference.
> 
> Signed-off-by: Evgeny Boger <boger@wirenboard.com>

I know Quentin has moved on from Bootlin, so looking for input from Chen-Yu Tsai
for these as I have no idea :)

I have pinged Quentin as well on off chance he still wants to take a look.

Jonathan

> ---
> 
> Notes:
>     Changes from v1:
>       - return scale factor of 1 as IIO_VAL_INT, not IIO_VAL_INT_PLUS_MICRO
>       - get rid of unused variable
> 
>  drivers/iio/adc/axp20x_adc.c | 18 +++---------------
>  1 file changed, 3 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/iio/adc/axp20x_adc.c b/drivers/iio/adc/axp20x_adc.c
> index 3e0c0233b431..df99f1365c39 100644
> --- a/drivers/iio/adc/axp20x_adc.c
> +++ b/drivers/iio/adc/axp20x_adc.c
> @@ -251,19 +251,8 @@ static int axp22x_adc_raw(struct iio_dev *indio_dev,
>  			  struct iio_chan_spec const *chan, int *val)
>  {
>  	struct axp20x_adc_iio *info = iio_priv(indio_dev);
> -	int size;
>  
> -	/*
> -	 * N.B.: Unlike the Chinese datasheets tell, the charging current is
> -	 * stored on 12 bits, not 13 bits. Only discharging current is on 13
> -	 * bits.
> -	 */
> -	if (chan->type == IIO_CURRENT && chan->channel == AXP22X_BATT_DISCHRG_I)
> -		size = 13;
> -	else
> -		size = 12;
> -
> -	*val = axp20x_read_variable_width(info->regmap, chan->address, size);
> +	*val = axp20x_read_variable_width(info->regmap, chan->address, 12);
>  	if (*val < 0)
>  		return *val;
>  
> @@ -386,9 +375,8 @@ static int axp22x_adc_scale(struct iio_chan_spec const *chan, int *val,
>  		return IIO_VAL_INT_PLUS_MICRO;
>  
>  	case IIO_CURRENT:
> -		*val = 0;
> -		*val2 = 500000;
> -		return IIO_VAL_INT_PLUS_MICRO;
> +		*val = 1;
> +		return IIO_VAL_INT;
>  
>  	case IIO_TEMP:
>  		*val = 100;