[PATCH] ALSA: dmaengine_pcm: Consider DMA cache caused delay in pointer callback

[Peter Ujfalusi]

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>
Reviewed-by: Takashi Iwai <tiwai@xxxxxxx>
Link: https://lore.kernel.org/r/20200210151402.29634-1-peter.ujfalusi@xxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
 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);
 	}
 
 	return bytes_to_frames(substream->runtime, pos);
-- 
2.20.1