| Message ID | 20200210140423.10232-1-peter.ujfalusi@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ASoC: dmaengine_pcm: Consider DMA cache caused delay in pointer callback | expand |
On Mon, 10 Feb 2020 15:04:23 +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, > > 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 | 6 ++++++ > sound/soc/soc-pcm.c | 2 +- > 2 files changed, 7 insertions(+), 1 deletion(-) > > diff --git a/sound/core/pcm_dmaengine.c b/sound/core/pcm_dmaengine.c > index 5749a8a49784..4f1395fd0160 100644 > --- a/sound/core/pcm_dmaengine.c > +++ b/sound/core/pcm_dmaengine.c > @@ -247,9 +247,15 @@ 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; > + int sample_bits = snd_pcm_format_physical_width(runtime->format); > + > buf_size = snd_pcm_lib_buffer_bytes(substream); > if (state.residue > 0 && state.residue <= buf_size) > pos = buf_size - state.residue; > + > + sample_bits *= runtime->channels; > + runtime->delay = state.in_flight_bytes / (sample_bits / 8); Can this be simply bytes_to_frames()? runtime->delay = bytes_to_frames(runtime, state.in_flight_bytes); > } > > return bytes_to_frames(substream->runtime, pos); > diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c > index ff1b7c7078e5..58ef508d70a3 100644 > --- a/sound/soc/soc-pcm.c > +++ b/sound/soc/soc-pcm.c > @@ -1151,7 +1151,7 @@ static snd_pcm_uframes_t soc_pcm_pointer(struct snd_pcm_substream *substream) > } > delay += codec_delay; > > - runtime->delay = delay; > + runtime->delay += delay; Is it correct? delay already takes runtime->delay as its basis, so it'll result in a double. thanks, Takashi
Hi Takashi, On 10/02/2020 16.21, Takashi Iwai wrote: > On Mon, 10 Feb 2020 15:04:23 +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, >> >> 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 | 6 ++++++ >> sound/soc/soc-pcm.c | 2 +- >> 2 files changed, 7 insertions(+), 1 deletion(-) >> >> diff --git a/sound/core/pcm_dmaengine.c b/sound/core/pcm_dmaengine.c >> index 5749a8a49784..4f1395fd0160 100644 >> --- a/sound/core/pcm_dmaengine.c >> +++ b/sound/core/pcm_dmaengine.c >> @@ -247,9 +247,15 @@ 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; >> + int sample_bits = snd_pcm_format_physical_width(runtime->format); >> + >> buf_size = snd_pcm_lib_buffer_bytes(substream); >> if (state.residue > 0 && state.residue <= buf_size) >> pos = buf_size - state.residue; >> + >> + sample_bits *= runtime->channels; >> + runtime->delay = state.in_flight_bytes / (sample_bits / 8); > > Can this be simply bytes_to_frames()? > > runtime->delay = bytes_to_frames(runtime, state.in_flight_bytes); Certainly it can, I looked at various helper but somehow missed the bytes_to_frames(). I'll send v2 in about an hour. > >> } >> >> return bytes_to_frames(substream->runtime, pos); >> diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c >> index ff1b7c7078e5..58ef508d70a3 100644 >> --- a/sound/soc/soc-pcm.c >> +++ b/sound/soc/soc-pcm.c >> @@ -1151,7 +1151,7 @@ static snd_pcm_uframes_t soc_pcm_pointer(struct snd_pcm_substream *substream) >> } >> delay += codec_delay; >> >> - runtime->delay = delay; >> + runtime->delay += delay; > > Is it correct? > delay already takes runtime->delay as its basis, so it'll result in a > double. The delay here is coming from the DAI and the codec. The runtime->delay hold the PCM (DMA) caused delay. > > thanks, > > Takashi > - Péter Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
On Mon, Feb 10, 2020 at 04:28:44PM +0200, Peter Ujfalusi wrote: > On 10/02/2020 16.21, Takashi Iwai wrote: > >> delay += codec_delay; > >> > >> - runtime->delay = delay; > >> + runtime->delay += delay; > > Is it correct? > > delay already takes runtime->delay as its basis, so it'll result in a > > double. > The delay here is coming from the DAI and the codec. > The runtime->delay hold the PCM (DMA) caused delay. I think Takashi's point here (and a query I have) is that we end up with delay = runtime->delay; delay += stuff; runtime->delay += delay; which is equivalent to runtime->delay = (runtime->delay * 2) + stuff; and that's a bit surprising.
On Mon, 10 Feb 2020 15:28:44 +0100, Peter Ujfalusi wrote: > > Hi Takashi, > > >> --- a/sound/soc/soc-pcm.c > >> +++ b/sound/soc/soc-pcm.c > >> @@ -1151,7 +1151,7 @@ static snd_pcm_uframes_t soc_pcm_pointer(struct snd_pcm_substream *substream) > >> } > >> delay += codec_delay; > >> > >> - runtime->delay = delay; > >> + runtime->delay += delay; > > > > Is it correct? > > delay already takes runtime->delay as its basis, so it'll result in a > > double. > > The delay here is coming from the DAI and the codec. > The runtime->delay hold the PCM (DMA) caused delay. Well, let's take a look at soc_pcm_pointer(): /* clearing the previous total delay */ runtime->delay = 0; offset = snd_soc_pcm_component_pointer(substream); /* base delay if assigned in pointer callback */ delay = runtime->delay; delay += snd_soc_dai_delay(cpu_dai, substream); for_each_rtd_codec_dai(rtd, i, codec_dai) { codec_delay = max(codec_delay, snd_soc_dai_delay(codec_dai, substream)); } delay += codec_delay; runtime->delay = delay; So, the code reads the current runtime->delay and saves it as delay variable. Then it adds the max delay from codec DAIs, and stores back to runtime->delay. If we change the last line to runtime->delay += delay; it'll add to the already existing value again, so it'll be doubly if runtime->delay was non-zero beforehand. That said, judging from the code, I believe the current soc-pcm.c code needs no change. thanks, Takashi
On 10/02/2020 16.37, Mark Brown wrote: > On Mon, Feb 10, 2020 at 04:28:44PM +0200, Peter Ujfalusi wrote: >> On 10/02/2020 16.21, Takashi Iwai wrote: > >>>> delay += codec_delay; >>>> >>>> - runtime->delay = delay; >>>> + runtime->delay += delay; > >>> Is it correct? >>> delay already takes runtime->delay as its basis, so it'll result in a >>> double. > >> The delay here is coming from the DAI and the codec. >> The runtime->delay hold the PCM (DMA) caused delay. > > I think Takashi's point here (and a query I have) is that we end up with > > delay = runtime->delay; > delay += stuff; > runtime->delay += delay; > > which is equivalent to > > runtime->delay = (runtime->delay * 2) + stuff; > > and that's a bit surprising. I see, I have missed what 9fb4c2bf130b ASoC: soc-pcm: Use delay set in component pointer function did. the soc-pcm part of the patch can be dropped then. - Péter Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
On 10/02/2020 16.38, Takashi Iwai wrote: > On Mon, 10 Feb 2020 15:28:44 +0100, > Peter Ujfalusi wrote: >> >> Hi Takashi, >> >>>> --- a/sound/soc/soc-pcm.c >>>> +++ b/sound/soc/soc-pcm.c >>>> @@ -1151,7 +1151,7 @@ static snd_pcm_uframes_t soc_pcm_pointer(struct snd_pcm_substream *substream) >>>> } >>>> delay += codec_delay; >>>> >>>> - runtime->delay = delay; >>>> + runtime->delay += delay; >>> >>> Is it correct? >>> delay already takes runtime->delay as its basis, so it'll result in a >>> double. >> >> The delay here is coming from the DAI and the codec. >> The runtime->delay hold the PCM (DMA) caused delay. > > Well, let's take a look at soc_pcm_pointer(): > > /* clearing the previous total delay */ > runtime->delay = 0; > > offset = snd_soc_pcm_component_pointer(substream); > > /* base delay if assigned in pointer callback */ > delay = runtime->delay; > > delay += snd_soc_dai_delay(cpu_dai, substream); > > for_each_rtd_codec_dai(rtd, i, codec_dai) { > codec_delay = max(codec_delay, > snd_soc_dai_delay(codec_dai, substream)); > } > delay += codec_delay; > > runtime->delay = delay; > > So, the code reads the current runtime->delay and saves it as delay > variable. Then it adds the max delay from codec DAIs, and stores back > to runtime->delay. > > If we change the last line to > runtime->delay += delay; > it'll add to the already existing value again, so it'll be doubly if > runtime->delay was non-zero beforehand. Yes, you are right. The change is added by 9fb4c2bf130b ASoC: soc-pcm: Use delay set in component pointer function which I have missed, apparently. > That said, judging from the code, I believe the current soc-pcm.c code > needs no change. Yes, there is no need to change soc-pcm. > > > thanks, > > Takashi > - Péter Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
diff --git a/sound/core/pcm_dmaengine.c b/sound/core/pcm_dmaengine.c index 5749a8a49784..4f1395fd0160 100644 --- a/sound/core/pcm_dmaengine.c +++ b/sound/core/pcm_dmaengine.c @@ -247,9 +247,15 @@ 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; + int sample_bits = snd_pcm_format_physical_width(runtime->format); + buf_size = snd_pcm_lib_buffer_bytes(substream); if (state.residue > 0 && state.residue <= buf_size) pos = buf_size - state.residue; + + sample_bits *= runtime->channels; + runtime->delay = state.in_flight_bytes / (sample_bits / 8); } return bytes_to_frames(substream->runtime, pos); diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c index ff1b7c7078e5..58ef508d70a3 100644 --- a/sound/soc/soc-pcm.c +++ b/sound/soc/soc-pcm.c @@ -1151,7 +1151,7 @@ static snd_pcm_uframes_t soc_pcm_pointer(struct snd_pcm_substream *substream) } delay += codec_delay; - runtime->delay = delay; + runtime->delay += delay; return offset; }
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, 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 | 6 ++++++ sound/soc/soc-pcm.c | 2 +- 2 files changed, 7 insertions(+), 1 deletion(-)