From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pierre-Louis Bossart Subject: Re: [PATCH 09/11] ASoC: Intel: Skylake: Fix DMA position reporting for capture stream Date: Thu, 23 Mar 2017 09:12:44 -0500 Message-ID: <8e50b63f-a9e7-537b-af1e-93e120d81ef9@linux.intel.com> References: <1490275926-2270-1-git-send-email-jeeja.kp@intel.com> <1490275926-2270-10-git-send-email-jeeja.kp@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mga06.intel.com (mga06.intel.com [134.134.136.31]) by alsa0.perex.cz (Postfix) with ESMTP id 75B6226721E for ; Thu, 23 Mar 2017 15:12:44 +0100 (CET) In-Reply-To: <1490275926-2270-10-git-send-email-jeeja.kp@intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: jeeja.kp@intel.com, alsa-devel@alsa-project.org Cc: Dharageswari R , tiwai@suse.de, Hardik T Shah , patches.audio@intel.com, broonie@kernel.org, liam.r.girdwood@intel.com List-Id: alsa-devel@alsa-project.org On 3/23/17 8:32 AM, jeeja.kp@intel.com wrote: > From: Hardik T Shah > > 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 > Signed-off-by: Hardik T Shah > Signed-off-by: Jeeja KP > --- > 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 > #include > +#include > #include > #include > #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... > + * 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; >