On Mon, 10 Feb 2020 16:14:02 +0100,
Peter Ujfalusi wrote:
>
> Some DMA engines can have big FIFOs which adds to the latency.
> The DMAengine framework can report the FIFO utilization in bytes. Use this
> information for the delay reporting.
>
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
> ---
> Hi,
>
> Changes since v1:
> - use bytes_to_frames() for the DMA delay calculation
> - Drop changes to soc-pcm
>
> 5.6-rc1 now have support for reporting the DMA cached data.
> With this patch we can include it to the delay calculation.
> The first DMA driver which reports this is the TI K3 UDMA driver.
>
> Regards,
> Peter
>
> sound/core/pcm_dmaengine.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/sound/core/pcm_dmaengine.c b/sound/core/pcm_dmaengine.c
> index 5749a8a49784..d8be7b488162 100644
> --- a/sound/core/pcm_dmaengine.c
> +++ b/sound/core/pcm_dmaengine.c
> @@ -247,9 +247,14 @@ snd_pcm_uframes_t snd_dmaengine_pcm_pointer(struct snd_pcm_substream *substream)
>
> status = dmaengine_tx_status(prtd->dma_chan, prtd->cookie, &state);
> if (status == DMA_IN_PROGRESS || status == DMA_PAUSED) {
> + struct snd_pcm_runtime *runtime = substream->runtime;
> +
> buf_size = snd_pcm_lib_buffer_bytes(substream);
> if (state.residue > 0 && state.residue <= buf_size)
> pos = buf_size - state.residue;
> +
> + runtime->delay = bytes_to_frames(runtime,
> + state.in_flight_bytes);
Another call of bytes_to_frames() below...
> }
>
> return bytes_to_frames(substream->runtime, pos);
... refers to substream->runtime.
Better to align both places, either runtime or substream->runtime.
With that minor nitpick, the change looks good:
Reviewed-by: Takashi Iwai <tiwai@xxxxxxx>
thanks,
Takashi
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