Re: D43399 FreeBSD Review, enable VCHIQ HDMI Audio subsystem for BCM2711 Raspberry Pi 4B, 400 adding 3 patch files.

Hello Marco,

Thanks for taking a look into it. I will try sox soon and do that l/r test.

Related to listening stereo, do you have any success test?

Cheers,

Marco Devesas Campos <[email protected]> escreveu (sábado,
27/12/2025 à(s) 19:21):

> Hi,
>
> For future reference, here's what's going on.
>
> Here's the driver code that get's called when you change the volume. You
> don't need to be a C guru to spot the problem:
>
>         static int
>         bcmmix_set(struct snd_mixer *m, unsigned dev, unsigned left,
> unsigned right)
>         {
>                 struct bcm2835_audio_info *sc = mix_getdevinfo(m);
>
>                 switch (dev) {
>                 case SOUND_MIXER_VOLUME:
>                         BCM2835_AUDIO_LOCK(sc);
>                         sc->volume = left;
>                         bcm2835_worker_update_params(sc);
>                         BCM2835_AUDIO_UNLOCK(sc);
>
>                 break;
>
>         default:
>                 break;
>         }
>
>                 return left | (left << 8);
>         }
>
> afaict, the sound subsystem code that calls this doesn't check the return
> value so that's why the output of `mixer` doesn't reflect what is going on
> in the driver.
>
> I checked the netbsd driver and it seems to be doing something similar
> [1], so this looks like a hardware shortcoming.
>
> You can check l/r separation with sox
>
>         play -n synth 3 sine 440 sine 0 #left
>         play -n synth 3 sine 0 sine 440 #right
>
> and that works fine for me.
>
>
> Best,
> Marco
>
> [1]:
> https://github.com/NetBSD/src/blob/e18008ace77d058ca7c3b2b5aab54fd9e8eee462/sys/arch/arm/broadcom/bcm2835_vcaudio.c#L650
>
> > On 16 Nov 2025, at 11:39, Nuno Teixeira <[email protected]> wrote:
> >
> > Hello Adrian,
> >
> > On my rpi4 connected via hdmi to external monitor.
> > Using headphones connected to monitor and I got sound!
> >
> > I noticed that only 1 channel can be listening in mono, i.e., I can hear
> both sides as mono.
> >
> > A simple test is to run:
> >
> > % mixer vol=0:1 (no sound at all)
> > % mixer vol=1:0 (sound on both sides, mono)
> >
> > NOTE: It could be a monitor/cable problem at my side, but it's worth to
> make this tests.
> >
> > vchiq0: <BCM2835 VCHIQ> mem 0x7e00b840-0x7e00b87b irq 78 on simplebus0
> >
> > % mixer
> > pcm0:mixer: <VCHIQ audio> at VCHIQ (play) (default)
> >     vol       = 1.00:1.00     pbk
> >
> > Thanks!
> >
> > Adrian Chadd <[email protected]> escreveu (sábado, 15/11/2025 à(s)
> 15:47):
> > hi!
> >
> > it's all in -HEAD now. Please update to get the support and lets get any
> other bugs shaken out!
> >
> >
> >
> > -adrian
> >
> >
> > On Mon, 27 Oct 2025 at 23:16, Adrian Chadd <[email protected]> wrote:
> > hi!
> >
> > so!
> >
> > * D36431 landed
> > * i've pulled the logging/tracing routines out of the big diff (D37878)
> into two smaller diffs (D53371 and D53372)
> > * I've pushed updates to D37878 to fix some style(9) stuff and pull out
> the code that's now in D53371 and D53372
> >
> > Now, the audio works fine out of the 3.5' jack. However if I load the
> system up (eg doing a buildkernel in parallel) then I saw the audio get
> stuck and then not ever restart.
> > I figure that we can tackle that once the above diffs have landed.
> >
> > I'll work with Andrew/Ed and whoever else on IRC is up for reviewing and
> getting D53371 and D53372 landed.
> >
> > The big diff is now around 1400 lines, which is still big and I can
> likely pull little bits and pieces of the diff out and land incrementally.
> >
> > But yes it is getting there! If you've got a rpi4 and you'd like to test
> this out (or you're running a 32 bit kernel on an older
> > RPI and want to verify these didn't break) then please give the diff
> stack at D37879 (four diffs) a go on the latest -head tree
> > and report back!
> >
> > Thanks again,
> >
> >
> > -adrian
> >
> >
> > --
> > Nuno Teixeira
> > FreeBSD UNIX:  <[email protected]>   Web:  https://FreeBSD.org
>
>

-- 
Nuno Teixeira
FreeBSD UNIX:  <[email protected]>   Web:  https://FreeBSD.org