Bug#978025: Sound issues with the 5.10.x kernel (alsa)

[Ryutaroh Matsumoto <ryutaroh@ict.e.titech.ac.jp>]

> 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.

Giving "enable_hdmi=0" to snd_bcm2835.ko does not improve the situation,
while module_blacklisting snd_bcm2835 suppresses all the symptoms reported.
snd_bcm2835.ko in 5.10.24 seems having a bug ignoring "enable_hdmi=0".

Best regards, Ryutaroh