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

Am 03.03.22 um 02:29 schrieb Chris Adams:
> Once upon a time, Stefan Wahren <stefan.wahren@i2se.com> 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:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.16.y&id=266423e60ea1b953fcc0cd97f3dad85857e434d1
>>
>> Unfortunately this is a change which requires this DTS fix:
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-5.16.y&id=c8013355ead68dce152cf426686f8a5f80d88b40
>>
>> So DTB and kernel must "match".
> Okay, so what's the best way to do that?
>
> I have EFI firmware from https://github.com/pftf/RPi4 in /boot/efi, and
> the /boot/dtb symlink removed. The bcm2711-rpi-4-b.dtb file in
> /boot/efi is from the RPi4_UEFI_Firmware_v1.32.zip 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.

Let me recap the situation. mainline and rpi vendor tree are independent
in development. Synchronization (incl. device tree) happens in both
directions.

U-Boot bootloader decided to keep an own copy of the mainline DT files
(which is currently based on an older 5.15 version which lacks the
gpio-ranges property). According to this statement [1] the EDK2 UEFI
decided to use the rpi vendor tree and don't care about the mainline DT
files.

I'm sorry but as a spare-time kernel developer, i don't have to time to
fight against all this mess.

I hope i will have some time for debugging in the near future ...

[1] - https://github.com/pftf/RPi4/issues/193

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