PCM3060 DAI driver ".format" value seems to be incorrect

[TommyTom]

Hi,

I am using a PCM3060 codec connected to a STM32MP135 MPU over I2S1 and I2C, and compiling STM Linux (v6.1) (along with STM's version of TF-A, Optee, and U-Boot) using Buildroot.

I had some trouble getting ALSA to output to the codec, it kept giving the response:

44004000.audio-controller-pcm3060-dac: ASoC: pcm3060-dac <-> 44004000.audio-controller No matching formats

I managed to work around the issue by changing the formats entry in snd_soc_dai_driver, in pcm3060.c (https://github.com/STMicroelectronics/linux/blob/7928f69738d2e57ee2a0dba6e9e680a3bf75ded9/sound/soc/codecs/pcm3060.c#L189) to SNDRV_PCM_FMTBIT_S32_LE.

#define PCM3060_FORMATS (SNDRV_PCM_FMTBIT_S32_LE)

static struct snd_soc_dai_driver pcm3060_dai[] = {
	{
		.name = "pcm3060-dac",
		.id = PCM3060_DAI_ID_DAC,
		.playback = {
			.stream_name = "Playback",
			.channels_min = 2,
			.channels_max = 2,
			.rates = PCM3060_DAI_RATES_DAC,
			.formats = PCM3060_FORMATS,
		},
		.ops = &pcm3060_dai_ops,
	},
	{
		.name = "pcm3060-adc",
		.id = PCM3060_DAI_ID_ADC,
		.capture = {
			.stream_name = "Capture",
			.channels_min = 2,
			.channels_max = 2,
			.rates = PCM3060_DAI_RATES_ADC,
			.formats = PCM3060_FORMATS,
		},
		.ops = &pcm3060_dai_ops,
	},
};

Everything seems to be working great now. I'm party posting here in case anybody else searches for the same problem, but also because I don't really understand the underlying cause of the problem. Is this a bug in STM's implementation of Linux, or the mainline driver? Or just a quirk of my set up? It's a fairly old chip but the code seems to still be maintained so I'm just wondering if I should report a bug or if I've just mucked something up in my configuration?

Thanks for any advice,

Tom

[Erwan SZYMANSKI · Accepted solution]

Hello @TommyTom,
Yes that's right. In fact in <kernel>/sound/soc/stm/stm32_i2s.c file, you can see this : 

static void stm32_i2s_dai_init(struct snd_soc_pcm_stream *stream,
			       char *stream_name)
{
	stream->stream_name = stream_name;
	stream->channels_min = 1;
	stream->channels_max = 2;
	stream->rates = SNDRV_PCM_RATE_8000_192000;
	stream->formats = SNDRV_PCM_FMTBIT_S16_LE |
				   SNDRV_PCM_FMTBIT_S32_LE;
}

The format is either SNDRV_PCM_FMTBIT_S16_LE or SNDRV_PCM_FMTBIT_S32_LE. Why ? Because our DMA only support these sizes of transfer. Explanation is here.

Kind regards, and thank you for this interesting sharing that can help other community members !

Erwan.

[TommyTom]

Thank you for the detailed response, that answers my question perfectly.

Tom