Wednesday, March 2, 2022

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

> 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.
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