vc4.ko brings unusable&unstable ALSA sinks

[Ryutaroh Matsumoto]

From: Ryutaroh Matsumoto <ryutaroh at ict.e.titech.ac.jp>
Subject: vc4.ko brings unusable&unstable ALSA sinks
Date: Fri, 26 Mar 2021 17:15:40 +0900 (JST)
> Touching vc4-hdmi-[01] too many times makes the kernel unstable,
> and shutting down often needs several minutes.
> /usr/bin/pulseaudio in its default setting touches all available  ALSA sinks
> and causes the above inconvenience.
> I mainly use HDMI audio output, and 

In my last email, a pointed reproducing procedure should have been given:

0. Assume an RPi4B and a high resolution HDMI display.
1. Install pulseaudio on a sensible distro with the upstream kernel and systemd,
    e.g.  https://raspi.debian.net
2. Make a non-root user and login as that user.
3. Run the following script by the non-root user:
#!/bin/sh
set -x
while true; do
  systemctl --user status pulseaudio
  pacmd list-sinks
  pacmd exit
  systemctl --user restart pulseaudio
done

Then every command in the above script gets stuck or fails.

I also prepared an SD card image that can reproduce the reported symptom
on RPi4B 8GB at http://153.240.174.134:64193/tmp/sdimage8GB.img.xz
(268,112,012 bytes).

Best regards, Ryutaroh