Internal microphone does not work with 5.12 (Tiger Lake, X1 Nano)

[Pierre-Louis Bossart]

>> arecord -fdat -vv -Dplugw:0,6 -c4 /dev/null
> 
> That does not work:
> 
> [15:55] nb3:~% arecord -fdat -vv -Dplugw:0,6 -c4 /dev/null
> ALSA lib pcm.c:2660:(snd_pcm_open_noupdate) Unknown PCM plugw:0,6
> arecord: main:830: audio open error: No such file or directory

typo: you need to use plughw:0,6 or just hw:0,6

> 
> However, recording with audacity produces to results:
> 
> - no sound recorded by default
> - sound recorded when I plugin an external headset
> 
> And using arecord -fdat -vv -c4 /dev/null (without -Dplugw) I get
> output, but the level is always 00% without the headset, ranges 02 ~ 90%
> with the headset plugged in.
> 
> I was wondering if there's a hardware switch "broken"
> for the detection of the headset and that's why the mic is muted
> internally?

No, the DMIC has nothing to do with the headset, it's an independent 
interface.