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: 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>

diff --git a/sound/core/pcm_dmaengine.c b/sound/core/pcm_dmaengine.c
index 5749a8a..d8be7b4 100644 (file)
--- 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);