Re: [PATCH 3/5] iio: adc: stm32-dfsdm: manage data resolution in trigger mode

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 19 Jun 2019 15:03:49 +0200
Olivier Moysan <olivier.moysan@st.com> wrote:

> Add output sample resolution management in scan mode.
> Add stm32_dfsdm_process_data() function to share sample
> processing between continuous and trigger modes.
> 
> Signed-off-by: Olivier Moysan <olivier.moysan@st.com>
Makes sense, though I would have preferred a little bit more info
on what the user visible effects fo this change are in
the patch description.  I think I know from reading the code,
but not every one will do that ;)

Applied to the togreg branch of iio.git and pushed out as
testing for the autobuilders to play with it.

Thanks,

Jonathan

> ---
>  drivers/iio/adc/stm32-dfsdm-adc.c | 41 ++++++++++++++++++++++++++-------------
>  1 file changed, 28 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
> index 6b90a40882f2..5b19a88412a6 100644
> --- a/drivers/iio/adc/stm32-dfsdm-adc.c
> +++ b/drivers/iio/adc/stm32-dfsdm-adc.c
> @@ -779,6 +779,30 @@ static unsigned int stm32_dfsdm_adc_dma_residue(struct stm32_dfsdm_adc *adc)
>  	return 0;
>  }
>  
> +static inline void stm32_dfsdm_process_data(struct stm32_dfsdm_adc *adc,
> +					    s32 *buffer)
> +{
> +	struct stm32_dfsdm_filter *fl = &adc->dfsdm->fl_list[adc->fl_id];
> +	struct stm32_dfsdm_filter_osr *flo = &fl->flo;
> +	unsigned int i = adc->nconv;
> +	s32 *ptr = buffer;
> +
> +	while (i--) {
> +		/* Mask 8 LSB that contains the channel ID */
> +		*ptr &= 0xFFFFFF00;
> +		/* Convert 2^(n-1) sample to 2^(n-1)-1 to avoid wrap-around */
> +		if (*ptr > flo->max)
> +			*ptr -= 1;
> +		/*
> +		 * Samples from filter are retrieved with 23 bits resolution
> +		 * or less. Shift left to align MSB on 24 bits.
> +		 */
> +		*ptr <<= flo->lshift;
> +
> +		ptr++;
> +	}
> +}
> +
>  static irqreturn_t stm32_dfsdm_adc_trigger_handler(int irq, void *p)
>  {
>  	struct iio_poll_func *pf = p;
> @@ -787,7 +811,9 @@ static irqreturn_t stm32_dfsdm_adc_trigger_handler(int irq, void *p)
>  	int available = stm32_dfsdm_adc_dma_residue(adc);
>  
>  	while (available >= indio_dev->scan_bytes) {
> -		u32 *buffer = (u32 *)&adc->rx_buf[adc->bufi];
> +		s32 *buffer = (s32 *)&adc->rx_buf[adc->bufi];
> +
> +		stm32_dfsdm_process_data(adc, buffer);
>  
>  		iio_push_to_buffers_with_timestamp(indio_dev, buffer,
>  						   pf->timestamp);
> @@ -806,8 +832,6 @@ static void stm32_dfsdm_dma_buffer_done(void *data)
>  {
>  	struct iio_dev *indio_dev = data;
>  	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
> -	struct stm32_dfsdm_filter *fl = &adc->dfsdm->fl_list[adc->fl_id];
> -	struct stm32_dfsdm_filter_osr *flo = &fl->flo;
>  	int available = stm32_dfsdm_adc_dma_residue(adc);
>  	size_t old_pos;
>  
> @@ -832,16 +856,7 @@ static void stm32_dfsdm_dma_buffer_done(void *data)
>  	while (available >= indio_dev->scan_bytes) {
>  		s32 *buffer = (s32 *)&adc->rx_buf[adc->bufi];
>  
> -		/* Mask 8 LSB that contains the channel ID */
> -		*buffer &= 0xFFFFFF00;
> -		/* Convert 2^(n-1) sample to 2^(n-1)-1 to avoid wrap-around */
> -		if (*buffer > flo->max)
> -			*buffer -= 1;
> -		/*
> -		 * Samples from filter are retrieved with 23 bits resolution
> -		 * or less. Shift left to align MSB on 24 bits.
> -		 */
> -		*buffer <<= flo->lshift;
> +		stm32_dfsdm_process_data(adc, buffer);
>  
>  		available -= indio_dev->scan_bytes;
>  		adc->bufi += indio_dev->scan_bytes;