systemd-backlight@backlight:amdgpu_bl0.service cant restore backlight, when using "quiet" kernel command option

[fabiscafe]

systemd version the issue has been seen with

systemd 246 (246.6-1-arch)
+PAM +AUDIT -SELINUX -IMA -APPARMOR +SMACK -SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +ZSTD +SECCOMP +BLKID +ELFUTILS +KMOD +IDN2 -IDN +PCRE2 default-hierarchy=hybrid

Used distribution

Arch Linux

Linux kernel version used (uname -a)

Linux frigg 5.9.8-zen1-1-zen #1 ZEN SMP PREEMPT Tue, 10 Nov 2020 22:44:06 +0000 x86_64 GNU/Linux
Linux frigg 5.9.8-arch1-1 #1 SMP PREEMPT Tue, 10 Nov 2020 22:44:11 +0000 x86_64 GNU/Linux

CPU architecture issue was seen on

x86_64

Expected behaviour you didn't see

backlight restore working

Unexpected behaviour you saw

Failed to start Load/Save Screen Backlight Brightness of backlight:amdgpu_bl0.

Steps to reproduce the problem

1. add "quiet" to your kernel commmand line
2. reboot

Journal with quiet:

journalctl -b -1 -u systemd-backlight@backlight:amdgpu_bl0.service
-- Logs begin at Thu 2020-09-17 08:15:00 CEST, end at Tue 2020-11-17 14:19:18 CET. --
Nov 17 14:15:15 frigg systemd[1]: Starting Load/Save Screen Backlight Brightness of backlight:amdgpu_bl0...
Nov 17 14:15:15 frigg systemd-backlight[325]: amdgpu_bl0: Failed to write system 'brightness' attribute: No such device or address
Nov 17 14:15:15 frigg systemd[1]: systemd-backlight@backlight:amdgpu_bl0.service: Main process exited, code=exited, status=1/FAILURE
Nov 17 14:15:15 frigg systemd[1]: systemd-backlight@backlight:amdgpu_bl0.service: Failed with result 'exit-code'.
Nov 17 14:15:15 frigg systemd[1]: Failed to start Load/Save Screen Backlight Brightness of backlight:amdgpu_bl0.

Right after login, I can do: systemctl start systemd-backlight@backlight:amdgpu_bl0.service and backlight got restored successfully

journal without quiet:

journalctl -b -u systemd-backlight@backlight:amdgpu_bl0.service
-- Logs begin at Thu 2020-09-17 08:15:00 CEST, end at Tue 2020-11-17 14:23:50 CET. --
Nov 17 14:15:57 frigg systemd[1]: Starting Load/Save Screen Backlight Brightness of backlight:amdgpu_bl0...
Nov 17 14:15:57 frigg systemd[1]: Finished Load/Save Screen Backlight Brightness of backlight:amdgpu_bl0.

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Upstream Bug link: https://bugzilla.kernel.org/show_bug.cgi?id=210263 (with workaround)

[poettering]

sounds like a driver bug. i.e. if the "brightness" sysfs attribute of the amdgpu driver returns ENXIO you get what you see.

Please ping amdgpu maintainers about this, i.e. why the advertise a brightness device that returns ENXIO.

[poettering]

Anyway, let's close this here. I doubt there's anything for us to fix here. If the driver people say otherwise, please report back and we can reopen, but from all i can see it's a driver problem if they advertise a brightness device that results in ENXIO