[TGL][DSM] pop noise happens at the beginning of recording when playback is triggered first

[keqiaozhang]

Describe the bug
when testing DSM, there's a sharp pop noise at the beginning of recording, this issue only happens when playback is triggered first, delay for a few seconds then trigger capture, you will hear that pop noise. But this pop noise was not captured in the wav file. the waveform of 4 channels are pure, even at the beginning.

To Reproduce

1. Enable loopback mode for DSM
   run:
   amp_enable.sh.txt

2. Trigger playback on speaker:

aplay -Dhw:0,0 -f s32_le -c 2 -r 48000 sine_48k_32bit.wav & 

3. Delay for a few seconds

sleep 2 

4. Trigger capture on speaker

arecord -Dhw:0,0 -f s32_le -c 4 -r 48000 dsm.wav 

Reproduction Rate
10/10

Expected behavior
no pop noise.

Environment
Driver: fce7f93 + #1971 + https://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound.git/commit/?h=for-next&id=914f674bec6efe42f9d6b036850a618fd1698290
Firmware:
SOF branch: tgl-005-drop-stable Commit: 277a9717
TPLG: sof-tgl-max98373-rt5682.tplg

dsm_dmesg.txt
dsm-logger.txt

[keyonjie]

This could be Max98373 configuration issue, as there is no change of the data(channel L/R) transmitting from the ASoC SSP to the codec (no noise in the captured file proved this), @sathya-nujella can Dhara help to check this with Maxim engineer, I can't assign this to Dhara as she is not in the SOF group, so assigning it to you.

[sathya-nujella]

Sure @keyonjie.

I am not able to assign to Dhara. Not sure what is the issue. When I search for her ID in assignee field.. it does not show up.
Can you please help why it is happening: this is her GH: https://github.com/RDharageswari

[keyonjie]

@sathya-nujella please ask Dhara to join the sof-developers team: https://github.com/orgs/thesofproject/people

@lgirdwood do we need invitation for that?

[naveen-manohar]

Adding @RDharageswari

[RDharageswari]

Thanks @naveen-manohar, i couldnt subscribe to the group.

[RDharageswari]

was able to capture the register dump when the issue happened.
exactly During the pop noise I see that the register 0x2024, has a value 0xd8 initially and changes to 0x98 later. Bit 6 & 7 corresponds to PCM_DATA_WIDTH[1:0] . [10 : 24-bit] & [11: 32 bit]. SSP1 on which the playback was ongoing was initially 32bit and when the capture started it changed to 24bit . Both pb & capture share the same I2S bus . this change can cause pop noise. Debugging WIP

[keyonjie]

good finding @RDharageswari .
maybe worth to try setting to 24/25 bit in below snippet for a quick try:

static int max98373_hw_params(struct snd_pcm_substream *substream,
			      struct snd_pcm_hw_params *params)
{
	struct snd_soc_pcm_runtime *rtd = substream->private_data;
	struct snd_soc_dai *codec_dai;
	int j;

	for_each_rtd_codec_dais(rtd, j, codec_dai) {
		if (!strcmp(codec_dai->component->name, MAX_98373_DEV0_NAME)) {
			/* DEV0 tdm slot configuration */
-			snd_soc_dai_set_tdm_slot(codec_dai, 0x3, 0x1, 8, 32);
+			snd_soc_dai_set_tdm_slot(codec_dai, 0x3, 0x1, 8, 25);

		}
		if (!strcmp(codec_dai->component->name, MAX_98373_DEV1_NAME)) {
			/* DEV1 tdm slot configuration */
-			snd_soc_dai_set_tdm_slot(codec_dai, 0xC, 0x2, 8, 32);
+			snd_soc_dai_set_tdm_slot(codec_dai, 0xC, 0x2, 8, 25);

		}
	}
	return 0;
}