Unverified Commit fa1f875c authored by Peter Ujfalusi's avatar Peter Ujfalusi Committed by Mark Brown
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ALSA: dmaengine_pcm: Consider DMA cache caused delay in pointer callback 



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: default avatarPeter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: default avatarTakashi Iwai <tiwai@suse.de>
Link: https://lore.kernel.org/r/20200210151402.29634-1-peter.ujfalusi@ti.com


Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 851fd873

sound/core/pcm_dmaengine.c

+5 −0
Original line number Diff line number Diff line
@@ -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);