>-----Original Message----- >From: Pierre-Louis Bossart [mailto:pierre-louis.bossart@xxxxxxxxxxxxxxx] >Sent: Thursday, March 23, 2017 7:13 AM >To: Kp, Jeeja <jeeja.kp@xxxxxxxxx>; alsa-devel@xxxxxxxxxxxxxxxx >Cc: R, Dharageswari <dharageswari.r@xxxxxxxxx>; tiwai@xxxxxxx; Shah, Hardik >T <hardik.t.shah@xxxxxxxxx>; Patches Audio <patches.audio@xxxxxxxxx>; >broonie@xxxxxxxxxx; Girdwood, Liam R <liam.r.girdwood@xxxxxxxxx> >Subject: Re: [PATCH 09/11] ASoC: Intel: Skylake: Fix DMA position >reporting for capture stream > >On 3/23/17 8:32 AM, 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. >> >> 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 | 22 ++++++++++++++++++++-- >> 1 file changed, 20 insertions(+), 2 deletions(-) >> >> diff --git a/sound/soc/intel/skylake/skl-pcm.c >b/sound/soc/intel/skylake/skl-pcm.c >> index ef440d8..149221c 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 +1064,30 @@ 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. > >is this really 20us regardless of the sampling frequency/channel count? >20us is one sample at 48kHz so wondering how generic this work-around is... Yes, this is independent of PCM parameters. 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; >> _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
