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ALSA: dmaengine_pcm: Consider DMA cache caused delay in pointer callback

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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@ti.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20200210151402.29634-1-peter.ujfalusi@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Peter Ujfalusi 2020-02-10 17:14:02 +02:00 committed by Mark Brown
parent 851fd87324
commit fa1f875c12
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1 changed files with 5 additions and 0 deletions
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5
sound/core/pcm_dmaengine.c
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@ -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);
}
return bytes_to_frames(substream->runtime, pos);