Wednesday, March 2, 2022

[fedora-arm] Re: Change in kernel PPS GPIO handling?

Once upon a time, Stefan Wahren <> said:
> Hi Chris,
> Am 02.03.22 um 10:51 schrieb Peter Robinson:
> >> I have an RPi4 running Fedora 35. It hadn't been updated in a while, so
> >> I applied updates today. When I boot to the kernel 5.16.11-200, I lose
> >> the PPS device from my GPS hat. Boot back to 5.14.16-301.fc35 and it
> >> works.
> >>
> >> I'm booting with EFI firmware, and with a device tree config.txt that
> > All our firmware are EFI, that's the only way we support booting, is
> > it the default U-Boot based one or are you using the edk2 one?
> >
> >> has "dtoverlay=pps-gpio,gpiopin=4" in it. I removed the /boot/dtb
> >> symlink and set /etc/u-boot.conf to not re-add it.
> >>
> >> When I boot 5.16, I see /proc/device-tree, and it has
> >> /proc/device-tree/pps@4 in it (and the contents look correct), but
> >> loading the pps-gpio kernel module just gives:
> >>
> >> pps-gpio: probe of pps@4 failed with error -22
> > Any chance you can tell us which kernel it started with, 5.14.x to
> > 5.16.x is a big window to debug and looking at kernel logs for
> > drivers/pps there's been no changes in that space in the 5.15+ kernels
> > at all.
> >
> > I wonder if it's a change/regression in the firmware overlay <->
> > kernel interface.
> do you use the DTB file from 5.14.x or 5.16x?
> I guess this is related to this commit:
> Unfortunately this is a change which requires this DTS fix:
> So DTB and kernel must "match".

Okay, so what's the best way to do that?

I have EFI firmware from in /boot/efi, and
the /boot/dtb symlink removed. The bcm2711-rpi-4-b.dtb file in
/boot/efi is from the file. I have a
config.txt in /boot/efi that references overlays in /boot/efi/overlays
from RPM bcm283x-overlays (like pps-gpio)..

I'm not quite sure how I need to fit all this together.
Chris Adams <>
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