On 30-04-19, 17:00, Sameer Pujar wrote:
> During the DMA transfers from memory to I/O, it was observed that transfers
> were inconsistent and resulted in glitches for audio playback. It happened
> because fifo size on DMA did not match with slave channel configuration.
>
> currently 'dma_slave_config' structure does not have a field for fifo size.
> Hence the platform pcm driver cannot pass the fifo size as a slave_config.
> Note that 'snd_dmaengine_dai_dma_data' structure has fifo_size field which
> cannot be used to pass the size info. This patch introduces fifo_size field
> and the same can be populated on slave side. Users can set required size
> for slave peripheral (multiple channels can be independently running with
> different fifo sizes) and the corresponding sizes are programmed through
> dma_slave_config on DMA side.
FIFO size is a hardware property not sure why you would want an
interface to program that?
On mismatch, I guess you need to take care of src/dst_maxburst..
>
> Request for feedback/suggestions.
>
> Signed-off-by: Sameer Pujar <spujar@xxxxxxxxxx>
> ---
> include/linux/dmaengine.h | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index d49ec5c..9ec198b 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -351,6 +351,8 @@ enum dma_slave_buswidth {
> * @slave_id: Slave requester id. Only valid for slave channels. The dma
> * slave peripheral will have unique id as dma requester which need to be
> * pass as slave config.
> + * @fifo_size: Fifo size value. The dma slave peripheral can configure required
> + * fifo size and the same needs to be passed as slave config.
> *
> * This struct is passed in as configuration data to a DMA engine
> * in order to set up a certain channel for DMA transport at runtime.
> @@ -376,6 +378,7 @@ struct dma_slave_config {
> u32 dst_port_window_size;
> bool device_fc;
> unsigned int slave_id;
> + u32 fifo_size;
> };
>
> /**
> --
> 2.7.4
--
~Vinod
