Re: [PATCH] Experimental vchiq and bcm2835_audio support for arm64

Hi Ronald,

Thanks so much for trying out the patch out.

> On 6 Feb 2022, at 13:05, Ronald Klop <ronald-lists@klop.ws> wrote:
> 
> Hi,
> 
> I compiled this on a RPI4 + 14-CURRENT. It boots, but I see no difference in available devices.
> I can try to boot it on a RPI3B+ on another time.

I *think* the GPU/VC in RPI-4 is a very different beast from the others. I'll
look into it, but if you could give it a try on the 3+ I'd be much obliged.

> 
> What would be the expected outcome? Where should I look at (or listen to)?
> 

You should see something like 

  vchiq0: <BCM2835 VCHIQ> mem 0x7e00b840-0x7e00b87b irq 54 on simplebus0
  vchiq: local ver 8 (min 3), remote ver 8.
  pcm0: <VCHIQ audio> on vchiq0

in your dmesg output.

The file /dev/vchiq should exist, as well as the following sysctl-s (I'm
assuming no other audio devices are attached)

  % sysctl dev.pcm
  dev.pcm.0.trace: 0
  ... 
  dev.pcm.0.dest: 0
  ... 
  dev.pcm.0.%parent: vchiq0
  ... 
  dev.pcm.0.%driver: pcm
  dev.pcm.0.%desc: VCHIQ audio
  …

Then if you `cat < /dev/random > /dev/dsp` you should hear some static coming
out of whatever is connected to hdmi (maybe headphones too? otherwise try
setting `sysctl dev.pcm.0.dest=1`)

Best,
Marco