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@ti.com

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@suse.de

thanks,

Takashi

The patch

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

has been applied to the asoc tree at

https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git for-5.7

All being well this means that it will be integrated into the linux-next tree (usually sometime in the next 24 hours) and sent to Linus during the next merge window (or sooner if it is a bug fix), however if problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing and review of the tree, please engage with people reporting problems and send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they should be sent as incremental updates against current git, existing patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying to this mail.

Thanks, Mark

From fa1f875c120fa44572c561d86022af2f6b0774c7 Mon Sep 17 00:00:00 2001

From: Peter Ujfalusi peter.ujfalusi@ti.com Date: Mon, 10 Feb 2020 17:14:02 +0200 Subject: [PATCH] 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 --- 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);