linux-kernel - Re: [PATCH 5/5] iio: adc: stm32-dfsdm: add comment for 16 bits record

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Message-ID: <20190622103307.50ba052b@archlinux>
Date:   Sat, 22 Jun 2019 10:33:07 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Olivier Moysan <olivier.moysan@...com>
Cc:     <knaack.h@....de>, <lars@...afoo.de>, <pmeerw@...erw.net>,
        <mcoquelin.stm32@...il.com>, <alexandre.torgue@...com>,
        <fabrice.gasnier@...com>, <linux-iio@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <benjamin.gaignard@...com>
Subject: Re: [PATCH 5/5] iio: adc: stm32-dfsdm: add comment for 16 bits
 record

On Wed, 19 Jun 2019 15:03:51 +0200
Olivier Moysan <olivier.moysan@...com> wrote:

> Add a comment on DMA configuration for 16 bits record.
> 
> Signed-off-by: Olivier Moysan <olivier.moysan@...com>
Applied.

Thanks,

Jonathan

> ---
>  drivers/iio/adc/stm32-dfsdm-adc.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
> index d855a605eab6..ee1e0569d0e1 100644
> --- a/drivers/iio/adc/stm32-dfsdm-adc.c
> +++ b/drivers/iio/adc/stm32-dfsdm-adc.c
> @@ -918,6 +918,11 @@ static void stm32_dfsdm_dma_buffer_done(void *data)
>  static int stm32_dfsdm_adc_dma_start(struct iio_dev *indio_dev)
>  {
>  	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
> +	/*
> +	 * The DFSDM supports half-word transfers. However, for 16 bits record,
> +	 * 4 bytes buswidth is kept, to avoid losing samples LSBs when left
> +	 * shift is required.
> +	 */
>  	struct dma_slave_config config = {
>  		.src_addr = (dma_addr_t)adc->dfsdm->phys_base,
>  		.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES,