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Is it possible to disable VC4 sound?
Hi,
Using the BRCM drivers, there's the "dtparam=audio=off" option in config.txt to disable loading the audio modules, but what's the way to do the same with the VC4 drivers? I am having problems with my HifiBerry DAC+ and I would like to disable the onboard audio. I suppose I could build a kernel without VC4 audio support, but I'm sure there must be a way to archieve the same without rebuilding the kernel, right?
Thanks
@popcornmix @pelwell Not quite sure what is wanted here. Is there such a thing as VC4 audio support? Nothing in the kernel config about it.
@vanfanel What do you mean by VC4 audio with regard to the Linux kernel?
The audio driver is bcm2835-audio, it's a module, so can you simply remove the module to disable it?
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I'm pretty sure he's referring to the HDMI audio support available from the VC4 driver, but why he couldn't reply to that effect beats me.
Audio is part of the regular vc4_hdmi driver, which is itself bundled into the overall vc4 module, so blacklisting won't work. It will skip the audio initialisation without failing to create everything else if the Device Tree node has no dmas property, but deleting a property isn't possible with an overlay. Fortunately a present-but-empty dmas doesn't make any sense, so we can modify the driver to treat an empty dmas the same as an absent one.
If @vanfanel shows an interest I can make that change and add an overlay parameter to control it, otherwise I have more important things to do.
@JamesH65 and @pelwell : I am VERY sorry I did nor reply earlier. I thought I had! Sorry.
I am referring to the VC4-related vc4-hdmi ALSA card, yes, not the bcm2835 ALSA card. The bcm2835 card works fine, and I know it can be disabled on config.txt very easily. But the vc4-hdmi audio card provided by the VC4 stack only seems to support one format and frequency:
https://github.com/raspberrypi/linux/issues/3043
So, yes, disabling the vc4-hdmi in config.txt card via an overlay parameter would be desirable. But even better would be having the vc4-hdmi audio card working instead of depending on the (deprecated?) bmc2835 interface.
Tweaking the driver and adding the overlay parameter is something I can do in a few minutes, getting the driver to work could take days/weeks for me.
@pelwell: I perfectly understand. Do you have an idea on why the vc4-hdmi driver only supports one audio format? Is it still being developed?
Is it still being developed?
Yes and no - it isn't finished (in that it isn't fully featured), but the developer isn't actively working on it.
@pelwell : This is shocking! The vc4 development is abandoned? What will be the graphics standard for the Pi then?
Others are being moved onto the project, but progress will be slow for a while.
Note: you can still use the legacy alsa driver with vc4-fkms-v3d (and vc4-kms-v3d). That is how LibreELEC is configured on Pi4.
@popcornmix : full vc4-kms-v3d is what I use on my projects involving small Pi systems. I know the legacy alsa driver (bmc2835) works fine with that, but having two ALSA drivers (legacy bmc2835 and vc4-hdmi) is causing problems, thats why I was asking if the non-working vc4-hdmi alsa driver could be somehow disabled.
I've pushed patches that should resolve this issue for you. They'll get picked up by future kernel builds.
@pelwell: Great! I hope one day we can rely on the vc4-hdmi ALSA driver... but for now, this will do!
The hardware only supports one format, and that is SNDRV_PCM_FMTBIT_IEC958_SUBFRAME_LE. Questions were asked on the relevant kernel mailing lists as to who or what should be responsible for adding that encapsulation when the client wants to provide something else, but no answers were forthcoming.
Duplication in all relevant drivers seems wrong and alsa should in theory support it, but getting the magic runes in asoundrc correct is non-trivial. There is some reference in https://anholt.livejournal.com/49474.html?nojs=1, but I can't find the kernel mailing list references at present. Memory says Pulseaudio will also deal with it all for you, and allows mixing of the streams prior to encapsulation which AIUI alsalib won't allow you to do.
@vanfanel this is in latest rpi-update kernel. Can you test? I think you want:
dtoverlay=vc4-kms-v3d,audio=off
@popcornmix : Yes! It works! :+1:
@6by9 : I put all the information I could find regarding a possible asoundrc here: https://github.com/raspberrypi/linux/issues/3043 There is a supposedly working asoundrc in: https://raw.githubusercontent.com/takaswie/alsa-lib/master/src/conf/cards/vc4-hdmi.conf ...but sadly it does not work for me. As you can see, I tried different combinations with no success... I believe ALSA can take care of format conversions.
Hey @popcornmix @vanfanel , with audio=off I just deactivate the brcm sound card, what do I have to deactivate vc4-hdmi soundcard? How can I add a present but empty dmas?
What are the entries in config.txt?
@AndistormEm As stated earlier in this thread,
dtoverlay=vc4-kms-v3d,audio=off
Also documented in the overlays README - https://github.com/raspberrypi/linux/blob/rpi-4.19.y/arch/arm/boot/dts/overlays/README#L2721
@6by9 Yes this is as I tried, but I deactivate brcm soundcard and not the vc4-hdmi
More information required from you. Kernel version, and Pi version for a start.
Pi 4, kernel 5.4.20
dtoverlay=vc4-kms-v3d
pi@raspberrypi:~ $ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: vc4hdmi [vc4-hdmi], device 0: MAI PCM vc4-hdmi-hifi-0 [MAI PCM vc4-hdmi-hifi-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: vc4hdmi1 [vc4-hdmi1], device 0: MAI PCM vc4-hdmi-hifi-0 [MAI PCM vc4-hdmi-hifi-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
dtoverlay=vc4-kms-v3d,audio=off
pi@raspberrypi:~ $ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: vc4hdmi1 [vc4-hdmi1], device 0: MAI PCM vc4-hdmi-hifi-0 [MAI PCM vc4-hdmi-hifi-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
dtoverlay=vc4-kms-v3d,audio=off,audio1=off
pi@raspberrypi:~ $ aplay -l
aplay: device_list:272: no soundcards found...
dtparam=audio=on would be the normal line for controlling the direct audio driver.
@AndistormEm Are you running a 5.4 kernel and not using a Pi 4? If so, I understand the problem. There were some recent changes to the way CMA is configured - it now uses Device Tree rather than kernel command line parameters - and the audio parameter in the 5.4 (and later) version of the vc4-kms-v3d overlay got broken.
There's a fixed version in the kernel source tree which will be in subsequent releases, but you can test it now.
- Download the source file: https://github.com/raspberrypi/linux/blob/rpi-5.4.y/arch/arm/boot/dts/overlays/vc4-kms-v3d-overlay.dts
- Compile it:
dtc -@ -I dts -O dtb -o vc4-kms-v3d.dtbo vc4-kms-v3d-overlay.dts - Install it:
sudo cp vc4-kms-v3d.dtbo /boot/overlays
I am running a 4.9 kernel, and now I understand. The 'audio' parameter hasn't been implemented in 4.9. So I have to look for another solution or update the kernel. Thanks @pelwell and @6by9 !!
Thank you to everyone who asked for or who added the command: dtoverlay=vc4-kms-v3d,audio=off
I have spent days trying to get a HiFiBerry Dac+ to work on a raspberry pie built on Bullseye and that command fixed the issue. For some reason not needed with Buster OS.
Thanks again.
I'd also like to disable VC4 audio, so my HiFiBerry becomes card 0.
However, when I add dtoverlay=vc4-kms-v3d,audio=off to config.txt as suggested above, it will only remove one of the vc4 devices (vc4hdmi0). vc4hdmi1 will still be present.
Any idea why that is?
With dtoverlay=vc4-kms-v3d:
$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: vc4hdmi0 [vc4-hdmi-0], device 0: MAI PCM i2s-hifi-0 [MAI PCM i2s-hifi-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: vc4hdmi1 [vc4-hdmi-1], device 0: MAI PCM i2s-hifi-0 [MAI PCM i2s-hifi-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 2: sndrpihifiberry [snd_rpi_hifiberry_digi], device 0: HifiBerry Digi HiFi wm8804-spdif-0 [HifiBerry Digi HiFi wm8804-spdif-0]
Subdevices: 0/1
Subdevice #0: subdevice #0
With dtoverlay=vc4-kms-v3d,audio=off:
$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: vc4hdmi1 [vc4-hdmi-1], device 0: MAI PCM i2s-hifi-0 [MAI PCM i2s-hifi-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 1: sndrpihifiberry [snd_rpi_hifiberry_digi], device 0: HifiBerry Digi HiFi wm8804-spdif-0 [HifiBerry Digi HiFi wm8804-spdif-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
It works for me - compare this:
pi@raspberrypi:~ $ grep kms /boot/config.txt
dtoverlay=vc4-kms-v3d
pi@raspberrypi:~ $ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Headphones [bcm2835 Headphones], device 0: bcm2835 Headphones [bcm2835 Headphones]
Subdevices: 8/8
Subdevice #0: subdevice #0
Subdevice #1: subdevice #1
Subdevice #2: subdevice #2
Subdevice #3: subdevice #3
Subdevice #4: subdevice #4
Subdevice #5: subdevice #5
Subdevice #6: subdevice #6
Subdevice #7: subdevice #7
card 1: vc4hdmi0 [vc4-hdmi-0], device 0: MAI PCM i2s-hifi-0 [MAI PCM i2s-hifi-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
card 2: vc4hdmi1 [vc4-hdmi-1], device 0: MAI PCM i2s-hifi-0 [MAI PCM i2s-hifi-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
with this:
pi@raspberrypi:~ $ grep kms /boot/config.txt
dtoverlay=vc4-kms-v3d,noaudio
pi@raspberrypi:~ $ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: Headphones [bcm2835 Headphones], device 0: bcm2835 Headphones [bcm2835 Headphones]
Subdevices: 8/8
Subdevice #0: subdevice #0
Subdevice #1: subdevice #1
Subdevice #2: subdevice #2
Subdevice #3: subdevice #3
Subdevice #4: subdevice #4
Subdevice #5: subdevice #5
Subdevice #6: subdevice #6
Subdevice #7: subdevice #7
What does uname -a report on your system?
Please forgive me, I'm sure you know this but I didn't until yesterday afternoon. Yesterday morning I found out about the command : dtoverlay=vc4-kms-v3d,audio=off And on my old pi with one HDMI port it fixed the issue. But, it made me look for vc4-kms-v3d and I found it in /boot/config.txt So now I go to /boot/config.txt and remove: dtparam=audio=on (on board audio) dtoverlay=vc4-kms-v3d (HDMI)
and reboot. No sound cards at all and no need for the new command either. This is before I add the driver for the HIFIBerry DAC. On a pi4 it removed all 3 cards ie. on board and two HDMI.
pi@LinnPi4:~ $ aplay -l aplay: device_list:274: no soundcards found...
I'm sorry, I'm sure you already know about this but I had to be sure, folks helped me.
Bob.
@pelwell Thanks! I see you are using noaudio instead of audio=off. I’ve updated my config accordingly and this did the trick!
Since I have also disabled onboard audio by removing dtparam=audio from config.txt, this leaves me with:
$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: sndrpihifiberry [snd_rpi_hifiberry_digi], device 0: HifiBerry Digi HiFi wm8804-spdif-0 [HifiBerry Digi HiFi wm8804-spdif-0]
Subdevices: 1/1
Subdevice #0: subdevice #0
Perfect!
For the record, uname -a is reporting the following:
Linux info-pi 5.10.63-v7l+ #1459 SMP Wed Oct 6 16:41:57 BST 2021 armv7l GNU/Linux