I have been trying to get the vc4_hdmi audio to work in my own aarch64 debian system with the latest raspberrypi kernel sources built for aarch64.
I am using the vc4 overlay (dtoverlay=vc4-kms-v3d).
aplay -l lists the vc4hdmi card as card 0, and if I set dtparam=audio=on on config.txt, the ALSA card (meaning the bcm2835 ALSA card) is also listed and of course it works fine using both hdmi and jack audio.
So, if I DON'T load the bcm2835 modules, am I supposed to get audio using vc4hdmi alone? I guess so, since it IS a card registered by the kernel that ALSA detects, but alsamixer says it has "no controls available", and no API (SDL2, libretro, etc) is able to make it sound.
I have seen that vc4hdmi audio was incorporated into the kernel back in 2017, and it IS supposed to be working by now, but I don't know if it's supposed to work without bcm2835 sound modules.
So, what am I misunderstanding here?