-----Original Message----- From: Pierre-Louis Bossart [mailto:pierre-louis.bossart@linux.intel.com] Sent: Thursday, March 23, 2017 7:13 AM To: Kp, Jeeja jeeja.kp@intel.com; alsa-devel@alsa-project.org Cc: R, Dharageswari dharageswari.r@intel.com; tiwai@suse.de; Shah, Hardik T hardik.t.shah@intel.com; Patches Audio patches.audio@intel.com; broonie@kernel.org; Girdwood, Liam R liam.r.girdwood@intel.com Subject: Re: [alsa-devel] [PATCH 09/11] ASoC: Intel: Skylake: Fix DMA position reporting for capture stream
On 3/23/17 8:32 AM, jeeja.kp@intel.com wrote:
From: Hardik T Shah hardik.t.shah@intel.com
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.
- 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@intel.com Signed-off-by: Hardik T Shah hardik.t.shah@intel.com Signed-off-by: Jeeja KP jeeja.kp@intel.com
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));snd_hdac_stream_get_pos_posbuf(hdac_stream(hstream));
}
if (pos >= hdac_stream(hstream)->bufsize) pos = 0;