Bug 210263

Summary: brightness device returns ENXIO (?) on brightness restore at boot, with bootoption "quiet"
Product: Drivers Reporter: Fabian (fabiscafe)
Component: Video(DRI - non Intel)Assignee: drivers_video-dri
Status: NEW ---    
Severity: normal CC: filip.hejsek, jaromir.obr, jplatte+linux, ninelore
Priority: P1    
Hardware: x86-64   
OS: Linux   
Kernel Version: 5.9.8 Subsystem:
Regression: No Bisected commit-id:
Attachments: dmesg

Description Fabian 2020-11-18 22:33:02 UTC 
Created attachment 293729 [details]
dmesg

Following: https://github.com/systemd/systemd/issues/17645

If I set kernel boot option "quiet", systemd fails to restore brightness level with error

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

At boot.

full journal output is: 

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.


This is an AMD Renoir system, with AMD Ryzen 5 4500U APU,

This happens only, if I set 'quiet' as boot option. If I remove it, brightness restore works fine.

If I boot with quiet set, after login I can do 

systemctl start systemd-backlight@backlight:amdgpu_bl0.service

And it will successfully restore my brightness level.
Comment 1 ninelore 2021-02-02 11:32:39 UTC 
Can confirm this with a Ryzen 7 4800H. Any news on this?
Comment 2 ninelore 2021-02-10 11:19:12 UTC 
I just found out that this Issue does NOT occur when you additionally add the fbcon=nodefer kernel parameter.
Comment 3 Fabian 2021-02-10 16:10:11 UTC 
(In reply to ninelore from comment #2)
> I just found out that this Issue does NOT occur when you additionally add
> the fbcon=nodefer kernel parameter.

This workaround works for me too.
Comment 4 Jonas Platte 2021-07-29 13:23:20 UTC 
Workaround works for me too, on a Lenovo Ideapad 530S-14ARR with an AMD Ryzen 2500U. I also set acpi_backlight=vendor to fix the same error message for backlight:acpi_video1. (No idea why it tries to restore backlight brightness twice)
Comment 5 Fabian 2021-12-02 08:35:38 UTC 
As of Kernel 5.15, I don't need fbcon=nodefer anymore. By default the backlight works and is set on start. I still get from time to time an boot-error by systemd, but that can be also worked around by loading amdgpu early.

Can someone confirm this?
Comment 6 jaromir.obr 2022-01-05 21:25:08 UTC 
@Fabian
I have the same experience. I was running kernel 5.13 on Ubuntu 21.10 and when I upgraded to mainline kernel 5.15.13 (using https://github.com/pimlie/ubuntu-mainline-kernel.sh), the service "systemd-backlight@backlight:amdgpu_bl0.service" starts as expected and backlight seems to be restored.

With kernel 5.13 it failed: "Failed to start Load/Save Screen Backlight Brightness of backlight:amdgpu_bl0" and I was not able to start it manually.
Comment 7 jaromir.obr 2022-01-08 13:05:56 UTC 
Related fix for resume from suspend in kernel 5.15 explained here: https://www.phoronix.com/scan.php?page=news_item&px=AMD-S2idle-Fix-Linux-5.15
The say it could also fix an issue with brightness.
Comment 8 ninelore 2022-01-12 15:08:49 UTC 
(In reply to Fabian from comment #5)
> As of Kernel 5.15, I don't need fbcon=nodefer anymore. By default the
> backlight works and is set on start. I still get from time to time an
> boot-error by systemd, but that can be also worked around by loading amdgpu
> early.
> 
> Can someone confirm this?

(In reply to jaromir.obr from comment #6)
> @Fabian
> I have the same experience. I was running kernel 5.13 on Ubuntu 21.10 and
> when I upgraded to mainline kernel 5.15.13 (using
> https://github.com/pimlie/ubuntu-mainline-kernel.sh), the service
> "systemd-backlight@backlight:amdgpu_bl0.service" starts as expected and
> backlight seems to be restored.
> 
> With kernel 5.13 it failed: "Failed to start Load/Save Screen Backlight
> Brightness of backlight:amdgpu_bl0" and I was not able to start it manually.

Can confirm this bug is fixed with 5.15