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

From: Jonathan Cameron <jic23@kernel.org>
To: Olivier Moysan <olivier.moysan@st.com>
Cc: lars@metafoo.de, alexandre.torgue@st.com,
	linux-iio@vger.kernel.org, pmeerw@pmeerw.net,
	linux-kernel@vger.kernel.org, mcoquelin.stm32@gmail.com,
	knaack.h@gmx.de, fabrice.gasnier@st.com,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org, benjamin.gaignard@st.com
Subject: Re: [PATCH 5/5] iio: adc: stm32-dfsdm: add comment for 16 bits record
Date: Sat, 22 Jun 2019 10:33:07 +0100	[thread overview]
Message-ID: <20190622103307.50ba052b@archlinux> (raw)
In-Reply-To: <1560949431-22948-6-git-send-email-olivier.moysan@st.com>

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

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


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