FAILED to start Load/Save #ness of backlight:acpi_video0

Support
#1

Hi, guys,

Got such kind of problem directly from installation phase:
FAILED to start Load/Save #ness of backlight:acpi_video0
in a final installation goes well, but after in case of restart it is about 50/50 if the screen starts or not.
Browsed forum for a solution and found topic with the same name, but no solution there.
Tried that from wiki Manjaro:
Reactivating_the_Backlight (can not add links :frowning: )
Also no result.

Have a ryzen 5 with Renoir GPU.

Maybe someone have any solution.

Thank you in advance!

#2

$ ls /sys/class/backlight

depending on kernel parameter and device, you might one that’s not named acpi_video0 but still there’s a systemd service for it, which of course will fail.

#3

The request gives me such result:
amdgpu_bl0

What it may mean? Sorry for mb newbee question. Used to had HP laptops before with Intel GPU and never had such kind of issues.

Kernel 5.8.16 (by Default after install)

#4

Meanwhile restarting appeared another problem:
Failed to start Light Display Manager (no longer call Backlight)
$ systemctl status lightdm writes the as on photo:

155201e0-3eaf-451f-95a9-7312a167d9b8
155201e0-3eaf-451f-95a9-7312a167d9b81599×1200 161 KB

#5

The request gives me such result:
amdgpu_bl0

What it may mean?

There’s no acpi_video0 device that controls your backlight, simply disable the corresponding service:

$ sudo systemctl disable systemd-backlight@backlight:acpi_video0.service

/sys/class/backlight lists all devices that control the backlight in your device, be it monitor or keyboard (if yours has any).

Meanwhile restarting appeared another problem:
Failed to start Light Display Manager (no longer call Backlight)

This is the display manager failing to start. Usually it doesn’t log very well because the logging is not its responsibility, but rather display system. In this case, move to a virtual terminal (ctrl+alt+f<2-6>, any number is fine), login and do:

$ grep EE /var/log/Xorg.0.log

It should explain why the display system crashes.

#6

$sudo lightdm --test-mode --debug
It launches the GUI, but next restart brings the same mistake again

8b05c347-f36f-45dd-9652-73272d0b1092
8b05c347-f36f-45dd-9652-73272d0b10921599×352 52.9 KB

Any advice?

Thank you in advance

#7

After
$ pacman -S xf86-video-vesa xf86-video-fbdev
Just Initializing extension MIT-SCREEN-SAVER left in the log.
But the same problem while restart
Failed to start Light Display Manager

#8

This means no more error from the driver side. It just coincidentally matches my ‘EE’ grep query due to ‘SCREEN’.

I just realized lightdm also has its own log directory. Could you check what’s inside /var/log/lightdm? Typically lightdm.log should exist, read its contents to find out why it keeps restarting.

#9