>-----Original Message----- >From: alsa-devel-bounces@xxxxxxxxxxxxxxxx [mailto:alsa-devel-bounces@alsa- >project.org] On Behalf Of Takashi Iwai >Sent: Friday, March 24, 2017 11:50 AM >To: Ughreja, Rakesh A <rakesh.a.ughreja@xxxxxxxxx> >Cc: alsa-devel@xxxxxxxxxxxxxxxx; R, Dharageswari <dharageswari.r@xxxxxxxxx>; >Patches Audio <patches.audio@xxxxxxxxx>; Shah, Hardik T ><hardik.t.shah@xxxxxxxxx>; broonie@xxxxxxxxxx; Girdwood, Liam R ><liam.r.girdwood@xxxxxxxxx>; Kp, Jeeja <jeeja.kp@xxxxxxxxx> >Subject: Re: [PATCH v2 09/11] ASoC: Intel: Skylake: Fix DMA >position reporting for capture stream > >On Fri, 24 Mar 2017 19:43:52 +0100, >Ughreja, Rakesh A wrote: >> >> >> >> >-----Original Message----- >> >From: alsa-devel-bounces@xxxxxxxxxxxxxxxx [mailto:alsa-devel- >bounces@alsa- >> >project.org] On Behalf Of Takashi Iwai >> >Sent: Friday, March 24, 2017 11:38 AM >> >To: Kp, Jeeja <jeeja.kp@xxxxxxxxx> >> >Cc: alsa-devel@xxxxxxxxxxxxxxxx; R, Dharageswari ><dharageswari.r@xxxxxxxxx>; >> >Patches Audio <patches.audio@xxxxxxxxx>; Shah, Hardik T >> ><hardik.t.shah@xxxxxxxxx>; broonie@xxxxxxxxxx; Girdwood, Liam R >> ><liam.r.girdwood@xxxxxxxxx> >> >Subject: Re: [PATCH v2 09/11] ASoC: Intel: Skylake: Fix DMA >> >position reporting for capture stream >> > >> >On Fri, 24 Mar 2017 18:40:32 +0100, >> >jeeja.kp@xxxxxxxxx wrote: >> >> >> >> From: Hardik T Shah <hardik.t.shah@xxxxxxxxx> >> >> >> >> As per hardware recommendation, for every capture stream completion >> >> following operations need to be done in order to reflect the actual >> >> data that is received in position buffer. >> >> >> >> 1. Wait for 20us before reading the DMA position in buffer once the >> >> interrupt is generated for stream completion. >> >> 2. Read any of the register to flush the DMA position value. This is >> >> dummy read operation. >> > >> >Are these workarounds needed for the legacy driver? >> >If yes, which chips require it? >> > >> >> Yes, these are needed in legacy driver as well. >> From SKL and BXT onwards, it is needed. > >OK, thanks for confirmation. > >Now, from what I read in the above, is the workaround required *only* >after the interrupt is generated? 20us delay isn't so cheap, and we >tend to inquire PCM positions often. If the workaround is needed only >after the PCM period elapse, we can set some flag in the irq handler >and apply the workaround only when necessary. > Yes, Takashi the workaround is required only in the period elapsed interrupt. In some cases the DMA Position updates are delayed and so when the period elapsed interrupt occurs the wait_for_avail thinks that one period worth of data is not available and so returns only on the next period elapsed interrupt. This creates problem for 2 periods playback/capture streams. So even in the period elapsed interrupt the wait is required only if the position is less than the period boundary. > >Takashi > >> >> > >> >thanks, >> > >> >Takashi >> > >> >> >> >> Signed-off-by: Dharageswari R <dharageswari.r@xxxxxxxxx> >> >> Signed-off-by: Hardik T Shah <hardik.t.shah@xxxxxxxxx> >> >> Signed-off-by: Jeeja KP <jeeja.kp@xxxxxxxxx> >> >> --- >> >> sound/soc/intel/skylake/skl-pcm.c | 23 +++++++++++++++++++++-- >> >> 1 file changed, 21 insertions(+), 2 deletions(-) >> >> >> >> diff --git a/sound/soc/intel/skylake/skl-pcm.c >> >b/sound/soc/intel/skylake/skl-pcm.c >> >> index ef440d8..1823197 100644 >> >> --- a/sound/soc/intel/skylake/skl-pcm.c >> >> +++ b/sound/soc/intel/skylake/skl-pcm.c >> >> @@ -21,6 +21,7 @@ >> >> >> >> #include <linux/pci.h> >> >> #include <linux/pm_runtime.h> >> >> +#include <linux/delay.h> >> >> #include <sound/pcm_params.h> >> >> #include <sound/soc.h> >> >> #include "skl.h" >> >> @@ -1063,13 +1064,31 @@ static snd_pcm_uframes_t >> >skl_platform_pcm_pointer >> >> * HAD space reflects the actual data that is transferred. >> >> * Use the position buffer for capture, as DPIB write gets >> >> * completed earlier than the actual data written to the DDR. >> >> + * >> >> + * For capture stream following workaround is required to fix the >> >> + * incorrect position reporting. >> >> + * >> >> + * 1. Wait for 20us before reading the DMA position in buffer once >> >> + * the interrupt is generated for stream completion as update happens >> >> + * on the HDA frame boundary i.e. 20.833uSec. >> >> + * 2. Read DPIB register to flush the DMA position value. This dummy >> >> + * read is required to flush DMA position value. >> >> + * 3. Read the DMA Position-in-Buffer. This value now will be equal to >> >> + * or greater than period boundary. >> >> */ >> >> - if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) >> >> + >> >> + if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) { >> >> pos = readl(ebus->bus.remap_addr + >> >AZX_REG_VS_SDXDPIB_XBASE + >> >> (AZX_REG_VS_SDXDPIB_XINTERVAL * >> >> hdac_stream(hstream)->index)); >> >> - else >> >> + } else { >> >> + udelay(20); >> >> + readl(ebus->bus.remap_addr + >> >> + AZX_REG_VS_SDXDPIB_XBASE + >> >> + (AZX_REG_VS_SDXDPIB_XINTERVAL * >> >> + hdac_stream(hstream)->index)); >> >> pos = >> >snd_hdac_stream_get_pos_posbuf(hdac_stream(hstream)); >> >> + } >> >> >> >> if (pos >= hdac_stream(hstream)->bufsize) >> >> pos = 0; >> >> -- >> >> 2.5.0 >> >> >> >> _______________________________________________ >> >> Alsa-devel mailing list >> >> Alsa-devel@xxxxxxxxxxxxxxxx >> >> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel >> >> >> >_______________________________________________ >> >Alsa-devel mailing list >> >Alsa-devel@xxxxxxxxxxxxxxxx >> >http://mailman.alsa-project.org/mailman/listinfo/alsa-devel >> >_______________________________________________ >Alsa-devel mailing list >Alsa-devel@xxxxxxxxxxxxxxxx >http://mailman.alsa-project.org/mailman/listinfo/alsa-devel _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
