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 <[email protected]>
---
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);
}
return bytes_to_frames(substream->runtime, pos);
--
Peter
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
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 <[email protected]>
> ---
> 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 <[email protected]>
thanks,
Takashi
On 10/02/2020 17.23, Takashi Iwai wrote:
> 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 <[email protected]>
>> ---
>> 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.
Sure, I'll use the runtime as with substream->runtime the delay part is
not nicely wrapping.
> With that minor nitpick, the change looks good:
> Reviewed-by: Takashi Iwai <[email protected]>
>
>
> thanks,
>
> Takashi
>
- Péter
Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
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 <[email protected]>
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 <[email protected]>
Reviewed-by: Takashi Iwai <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mark Brown <[email protected]>
---
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