[PATCH 4.19 176/361] ASoC: AMD: Fix capture unstable in beginning for some runs

Greg Kroah-Hartman
2018-11-11T22:28:07Z

From: Akshu Agrawal <akshu.agrawal@amd.com>

[ Upstream commit c50535ed6a10fcae1b64ae83c0f6b1eeb5535afc ]

alsa_conformance_test -C hw:0,4 -p 1024 --debug
would sometime show:
TIME_DIFF(s) HW_LEVEL READ RATE
0.000095970 1024 1024 10670001.041992
0.042609555 1024 2048 24032.168372
0.021330364 1024 3072 48006.681930
0.021339559 1024 4096 47985.996337
The issue is that in dma pointer function we can have stale value
of the register for current descriptor of channel.
The register retains the number of the last descriptor that
was transferred.

Fix ensures that we report position, 0, till the one period worth of
data is transferred. After one period of data, in handler of period
completion interrupt we update the config and correct value of descriptor
starts reflecting.

Signed-off-by: Akshu Agrawal <akshu.agrawal@amd.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
sound/soc/amd/acp-pcm-dma.c | 22 ++++++++++++++--------
1 file changed, 14 insertions(+), 8 deletions(-)

--- a/sound/soc/amd/acp-pcm-dma.c
+++ b/sound/soc/amd/acp-pcm-dma.c
@@ -1036,16 +1036,22 @@ static snd_pcm_uframes_t acp_dma_pointer

if (substream->stream == SNDRV_PCM_STREAM_CAPTURE) {
period_bytes = frames_to_bytes(runtime, runtime->period_size);
- dscr = acp_reg_read(rtd->acp_mmio, rtd->dma_curr_dscr);
- if (dscr == rtd->dma_dscr_idx_1)
- pos = period_bytes;
- else
- pos = 0;
bytescount = acp_get_byte_count(rtd);
- if (bytescount > rtd->bytescount)
+ if (bytescount >= rtd->bytescount)
bytescount -= rtd->bytescount;
- delay = do_div(bytescount, period_bytes);
- runtime->delay = bytes_to_frames(runtime, delay);
+ if (bytescount < period_bytes) {
+ pos = 0;
+ } else {
+ dscr = acp_reg_read(rtd->acp_mmio, rtd->dma_curr_dscr);
+ if (dscr == rtd->dma_dscr_idx_1)
+ pos = period_bytes;
+ else
+ pos = 0;
+ }
+ if (bytescount > 0) {
+ delay = do_div(bytescount, period_bytes);
+ runtime->delay = bytes_to_frames(runtime, delay);
+ }
} else {
buffersize = frames_to_bytes(runtime, runtime->buffer_size);
bytescount = acp_get_byte_count(rtd);