Sound issues with the 5.10.x kernel (alsa)

[Ryutaroh Matsumoto]

Hi all,

From: Stefan Wahren <stefan.wahren at i2se.com>
Subject: Re: Sound issues with the 5.10.x kernel (alsa)
Date: Mon, 8 Feb 2021 13:22:56 +0100
>> This is basically me forwarding the bug I reported on Debian's BTS:
>> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=978025
>> TL;DR: I have a RPi 3B+ running pure Debian Bullseye arm64 (~from 
>> raspi.debian.net), named rpi-mpd, connected via HDMI cable to my AV Receiver.
> can you please confirm that the bcm2835-audio driver causing the issues?

I think the root cause of this issue is that both vc4.ko and snd_bcm2835.ko
try to provide ALSA sinks to HDMI audio outputs from RPi.
Why do the two drivers provide the same functionality for the same device?
It seems nonsense.
There must be some coordination between vc4.ko and snd_bcm2835.ko
on who provides ALSA sinks of RPi HDMI output.

The non-coordination that both drivers provide different ALSA sinks of the same
device already causes another symptom as
http://lists.infradead.org/pipermail/linux-rpi-kernel/2021-March/008077.html

Best regards, Ryutaroh Matsumoto