[Wayland] Screen blanks for a second whenever discrete GPU is powered up

[Chris Halse Rogers]

On this Kaby Lake G laptop, GNOME Shell blanks the screen for a second each time the AMD GPU is powered up. Triggers for powering up include: launching something which loads GL such as Steam or glxinfo, loading the Display configuration page, and so on.

This behaviour does *not* occur with GNOME Shell under X, so it's probably something to do with mutter's KMS interactions.

Because the GPU powers down quite aggressively (I think it's about 5sec without activity) this can be quite annoying :)

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: gnome-shell 3.33.91-1ubuntu1
ProcVersionSignature: Ubuntu 5.1.0+bcachefs.git20190828.bc3a6a71-1-generic 5.1.2
Uname: Linux 5.1.0+bcachefs.git20190828.bc3a6a71-1-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu7
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Fri Aug 30 09:48:25 2019
DisplayManager: gdm3
InstallationDate: Installed on 2019-08-29 (0 days ago)
InstallationMedia: Ubuntu 19.10 bcachefs (20190828)
RelatedPackageVersions: mutter-common 3.33.91-1ubuntu1
SourcePackage: gnome-shell
UpgradeStatus: No upgrade log present (probably fresh install)

[Daniel van Vugt (vanvugt)]

Can you tell if the "blanking" is either:

  * The output entering sleep mode; or
  * A black frame being accidentally flipped.

I guess checking if the backlight is still on would answer that.

[Daniel van Vugt (vanvugt)]

or

  * An invalid framebuffer being accidentally flipped.

[Chris Halse Rogers (raof)]

It looks like modesetting, or at least a destructive probe of the attached displays.

There's nothing KMS related in dmesg corresponding to the blanking, so I don't think it's an invalid FB (I'd expect i915 to spit something in dmesg in that case)

[Daniel van Vugt (vanvugt)]

A black frame can also mean a zero FB ID, IIRC...

Can you tell if the backlight is going off?

[Daniel van Vugt (vanvugt)]

Regardless, please also create an upstream bug:

  https://gitlab.gnome.org/GNOME/mutter/issues

[Daniel van Vugt (vanvugt)]

Thank you for reporting this bug to Ubuntu.
Ubuntu 19.10 (eoan) reached end-of-life on July 17, 2020.

See this document for currently supported Ubuntu releases:
https://wiki.ubuntu.com/Releases

We appreciate that this bug may be old and you might not be interested in discussing it any more. But if you are then please upgrade to the latest Ubuntu version and re-test. If you then find the bug is still present in the newer Ubuntu version, please add a comment here telling us which new version it is in and change the bug status to Confirmed.