Screen doesn't turn off when using Wayland on some devices

[Gabriel Ionescu]

When the screen of my laptop (Thinkpad E480) is supposed to turn off (because of inactivity or when actively locking screen), the screen dims, turns off for a second and then turns back on while remaining dimmed. I can see the backlight of the screen and the cursor.

This bug is only present when using a wayland-session regardless of my settings. It also happens with a fresh user account. Additionally, I tested with the 5.8 and 5.12 kernels with the same result.

ProblemType: Bug
DistroRelease: Ubuntu 21.04
Package: gnome-power-manager 3.32.0-2
ProcVersionSignature: Ubuntu 5.11.0-17.18-generic 5.11.12
Uname: Linux 5.11.0-17-generic x86_64
ApportVersion: 2.20.11-0ubuntu65.1
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Wed May 26 08:13:27 2021
InstallationDate: Installed on 2021-05-24 (1 days ago)
InstallationMedia: Ubuntu 21.04 "Hirsute Hippo" - Release amd64 (20210420)
SourcePackage: gnome-power-manager
UpgradeStatus: No upgrade log present (probably fresh install)

[Gabriel Ionescu (justoneslave)]

I tested with Fedora 34 (Gnome 40) and I get exactly the same result.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[mx80 (rzach)]

Same problem on Asus Zenbook 14/Ubuntu 21.04. Backlight stays on even in Suspend mode. Did not have that problem with 20.04

[Zac Schramm (zacman55)]

Also having this issue with Intel Nuc NUC5i5RYK with Fedora 34. Worked before on KDE.

[Gabriel Ionescu (justoneslave)]

Problem is still present with Ubuntu 21.10. I also tested Fedora with Gnome 41 and experienced the same behavior.

[Gabriel Ionescu (justoneslave)]

I issued a bug report on GitLab: https://gitlab.gnome.org/GNOME/mutter/-/issues/1991

[Daniel van Vugt (vanvugt)]

I noticed in the source code recently that power saving modes are implemented differently in atomic KMS, which only got switched on recently. Maybe try turning that off in /etc/environment to see if the problem is specific to atomic KMS:

  MUTTER_DEBUG_ENABLE_ATOMIC_KMS=0

and then reboot.

[Gerry Paradis (volksdude)]

I added :
MUTTER_DEBUG_ENABLE_ATOMIC_KMS=0
in /etc/environment and rebooted.

It didn't fix the problem...

[Gabriel Ionescu (justoneslave)]

In my case, adding MUTTER_DEBUG_ENABLE_ATOMIC_KMS=0 to /etc/environment worked. After reboot, the screen turns off and stays off. I will do further testing if this has some side effects.

[Daniel van Vugt (vanvugt)]

Gerry, please follow the instructions in bug 1949262 instead.

[Daniel van Vugt (vanvugt)]

Fixed in GNOME 42:
https://gitlab.gnome.org/GNOME/mutter/-/issues/1991#note_1427109