linux-kernel - [PATCH] ASoC: Intel: Atom: read timestamp moved to period

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Message-Id: <20190709040147.111927-1-levinale@chromium.org>
Date:   Mon,  8 Jul 2019 21:01:47 -0700
From:   Alex Levin <levinale@...omium.org>
To:     alsa-devel@...a-project.org
Cc:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
        Jie Yang <yang.jie@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Alex Levin <levinale@...omium.org>,
        linux-kernel@...r.kernel.org, benzh@...omium.org,
        cujomalainey@...omium.org
Subject: [PATCH] ASoC: Intel: Atom: read timestamp moved to period_elapsed

sst_platform_pcm_pointer is called from both snd_pcm_period_elapsed and
from snd_pcm_ioctl. Calling read timestamp results in recalculating
pcm_delay and buffer_ptr (sst_calc_tstamp) which consumes buffers in a
faster rate than intended.
In a tested BSW system with chtrt5650, for a rate of 48000, the
measured rate was sometimes 10 times more than that.
After moving the timestamp read to period elapsed, buffer consumption is
as expected.

Signed-off-by: Alex Levin <levinale@...omium.org>
---
 sound/soc/intel/atom/sst-mfld-platform-pcm.c | 23 +++++++++++++-------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/sound/soc/intel/atom/sst-mfld-platform-pcm.c b/sound/soc/intel/atom/sst-mfld-platform-pcm.c
index 0e8b1c5eec88..196af0b30b41 100644
--- a/sound/soc/intel/atom/sst-mfld-platform-pcm.c
+++ b/sound/soc/intel/atom/sst-mfld-platform-pcm.c
@@ -265,16 +265,28 @@ static void sst_period_elapsed(void *arg)
 {
 	struct snd_pcm_substream *substream = arg;
 	struct sst_runtime_stream *stream;
-	int status;
+	struct snd_soc_pcm_runtime *rtd;
+	int status, ret_val;
 
 	if (!substream || !substream->runtime)
 		return;
 	stream = substream->runtime->private_data;
 	if (!stream)
 		return;
+
+	rtd = substream->private_data;
+	if (!rtd)
+		return;
+
 	status = sst_get_stream_status(stream);
 	if (status != SST_PLATFORM_RUNNING)
 		return;
+
+	ret_val = stream->ops->stream_read_tstamp(sst->dev, &stream->stream_info);
+	if (ret_val) {
+		dev_err(rtd->dev, "stream_read_tstamp err code = %d\n", ret_val);
+		return;
+	}
 	snd_pcm_period_elapsed(substream);
 }
 
@@ -658,20 +670,15 @@ static snd_pcm_uframes_t sst_platform_pcm_pointer
 			(struct snd_pcm_substream *substream)
 {
 	struct sst_runtime_stream *stream;
-	int ret_val, status;
+	int status;
 	struct pcm_stream_info *str_info;
-	struct snd_soc_pcm_runtime *rtd = substream->private_data;
 
 	stream = substream->runtime->private_data;
 	status = sst_get_stream_status(stream);
 	if (status == SST_PLATFORM_INIT)
 		return 0;
+
 	str_info = &stream->stream_info;
-	ret_val = stream->ops->stream_read_tstamp(sst->dev, str_info);
-	if (ret_val) {
-		dev_err(rtd->dev, "sst: error code = %d\n", ret_val);
-		return ret_val;
-	}
 	substream->runtime->delay = str_info->pcm_delay;
 	return str_info->buffer_ptr;
 }
-- 
2.22.0.410.gd8fdbe21b5-goog