Sound issues with the 5.10.x kernel (alsa)

[Diederik de Haas]

On dinsdag 16 februari 2021 01:12:12 CET Diederik de Haas wrote:
> On maandag 8 februari 2021 13:22:56 CET Stefan Wahren wrote:
> > Currently i cannot see any of the fixes by Phil
> > Elwell in linux-stable. Maybe they won't apply and needs to be backport
> > manually.
> > 
> > Just for reference here are the revelant patches:
> > 
> > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit
> > /d
> > rivers/staging/vc04_services?h=next-20210205&id=96ae327678eceabf455b11a88
> > ba1 4ad540d4b046
> > 
> > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit
> > /d
> > rivers/staging/vc04_services?h=next-20210205&id=88753cc19f087abe0d39644b8
> > 44e 67a59cfb5a3d
> > 
> > Could you please try?

I've cherry-picked both patches on top of 5.10.16 and they apply cleanly.
 
> I've now successfully build and booted a 5.10.16 kernel 'pristine' and with
> the above mentioned patches.
> In the 'pristine' variant, I had the same bad/horrible quality as I
> experienced with Debian's 5.10 kernels.
> The 'patched' variant seems to be a tad better, but didn't completely solve
> the audio problem. There's still some noise intermixed with the music and
> other artifacts, but I'm inclined to think it's not as horrible as before.
> 
> I'll do some more hearing tests tomorrow when I'm fresh again, but figured
> I'd share these preliminary results already.

It may have been wishful thinking. 
If there is a difference then isn't big like night and day that would make 
sound play properly. 
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=935456#33 also mentions
that digital audio is not working on arm64, but does work with armhf.

What is bloody annoying is that the sequence of the sound cards keep 
switching, which in turn means I have to check the config and enable or 
disable the settings in /etc/asound.conf to make ALSA use the ALSA card.
The net result is that instead of being able to compare the sounds within 
(say) 1 minute, it takes 3 minutes, 'just' too long to (easily) compare.

diederik at rpi-mpd:~$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: vc4hdmi [vc4-hdmi], device 0: MAI PCM vc4-hdmi-hifi-0 [MAI PCM vc4-hdmi-hifi-0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
  Subdevices: 6/7
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
card 1: ALSA [bcm2835 ALSA], device 1: bcm2835 IEC958/HDMI [bcm2835 IEC958/HDMI]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

My rpi-mpd device is connected to my multichannel audio capable AV receiver. 
Is one of these cards capable of just passing through the bitstream? 
If so, which. And how?

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