videocore: failed to open the mailbox to the GPU: open /dev/vcio: no such file or directory

[mpictor]

I'm able to toggle GPIOs on and off, but when I try PWM I get this error:

bcm283x-gpio (GPIO20): videocore: failed to open the mailbox to the GPU: open /dev/vcio: no such file or directory

some googling led me to raspberrypi/linux#4620, so applying the linked patches may fix it.
These look to be the latest from pelwell:
vcio driver raspberrypi/linux@ac4fd05
dts raspberrypi/linux@aa901b4

On rpi3b+

[stapelberg]

AFAICT, the vcio driver is not upstreamed to Linux, and only available in the Raspberry Pi Foundation’s linux kernel fork.

gokrazy uses the upstream Linux kernel, and I’m not sure if there is a way to use PWM with it. Are you using periph.io, or which library are you using to use GPIOs?

If you want to use the Raspberry Pi foundation kernel instead of gokrazy’s kernel, there is a community-supported repository for it: https://gokrazy.org/platforms/#community-supported-raspberry-pi-os-32-bit-kernelfirmware

[mpictor]

I am using periph.io - specifically, bcm283x.Pin.PWM() from periph.io/x/host/v3 v3.7.2

I'd tried a while back to add a patch for vcio, but couldn't get its device to show up. It hadn't occurred to me that the device tree would also need updating, as device trees aren't something I've done much with.

I'll try to find and update that patch, and figure out what files are needed for dt. I hope I can just copy over the bcm*-rpi* dts files without breaking anything...

[willgorman]

@mpictor Were you ever able to get PWM working with the standard gokrazy kernel?