2010/3/2 Peter Ujfalusi <peter.ujfalusi@xxxxxxxxx> > Hello, > > There has been discussion in alsa-devel in this subject several times, > but no actual patches has been sent. > > Based on the available information the latency caused by the HW buffer > on some systems can be handled by updating the runtime->delay. > > It has been discussed, that the runtime->delay can also be updated > dynamically to show more accurate delay. > > To further complicate things, in ASoC we could have more buffer in the > chain. To handle this we need soc level support. > > This RFC series tries to do that in soc by: > - introducing a pcm_pointer wrapper > - in this wrapper we call the original pcm_pointer functions to get the > DMA pointer > - introducing a new interface in dai_ops to ask the delay from the dais > - adding the cpu_dai and codec_dai returned delay to form the actual > delay > - update the runtime->delay with this value. > > With this approach none of the existing drivers need change, but they > can add support for specifying the FIFO caused delay. > > In this series on top of the core changes the omap(3) code is updated > to take this delay reporting into use. > I have not added the support to the tlv320dac33 codec driver, since it > needs a bit more work, but along the same line it can be done, and if > the tlv320dac33 is hooked to omap McBSP than applications can know the > whole delay/latency on that path. > > Since this is for RFC, I have based it on sound-2.6 topc/asoc branch, > which does not have the McBSP regcache nor the sidetone patches, but I > would like to get feedback on this method first than create a proper > series. > > I have left out linux-omap from this RFC round, since the problem > is ALSA related. > > Thank you, > Péter Ujfalusi > > --- > Peter Ujfalusi (4): > ASoC: core: soc level wrapper for pcm_pointer callback > ASoC: core: Add delay operation to snd_soc_dai_ops > OMAP3: McBSP: Add interface for transmit FIFO state query > ASoC: OMAP3: Report delay on playback caused by the internal FIFO > > arch/arm/plat-omap/include/plat/mcbsp.h | 4 +++ > arch/arm/plat-omap/mcbsp.c | 27 ++++++++++++++++++++++++ > include/sound/soc-dai.h | 6 +++++ > sound/soc/omap/omap-mcbsp.c | 26 +++++++++++++++++++++++ > sound/soc/soc-core.c | 34 > ++++++++++++++++++++++++++++++- > 5 files changed, 96 insertions(+), 1 deletions(-) > > > Do soc support snd_pcm_rewind() and snd_pcm_forward ? _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
