Heavy screen tearing in Wayland sessions on Raspberry Pi 4-B

[Daniel van Vugt]

Heavy screen tearing in Wayland sessions on Raspberry Pi 4-B when using the FMKS driver, meaning you have:

  dtoverlay=vc4-fkms-v3d

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1896167

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Daniel van Vugt (vanvugt)]

I've read a suggestion this is fixed in later kernels like 5.9. Need to test.

[Daniel van Vugt (vanvugt)]

It's kernel 5.10 apparently.

[Launchpad Janitor (janitor)]

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

[Juliane (juliane11)]

I can confirm this bug.

I'm using:
- Raspberry Pi 4B 8GB
- Ubuntu 20.10 Desktop

Choosing "Ubuntu on Wayland" as Desktop at the login-screen, I can login.
- Opening "files" works (I get a normal window)
- But, opening Firefox/Gimp/etc brings up broken windows (see attachment)

[Daniel van Vugt (vanvugt)]

Juliane,

That's not tearing, it's corruption. See bug 1896171 instead.

[Daniel van Vugt (vanvugt)]

The tearing still happens in hirsute, but only when you can convince the system to render at 60Hz. Most of the time it's stuttering (30Hz) and not tearing.

[Daniel van Vugt (vanvugt)]

Seems to depend on clock frequency, just like I see with Intel graphics. If you spin the CPU at 100% like:

  while true; do true; done

then the clock frequencies increase and desktop frame rates become very smooth. But that's also when the tearing starts.

[Daniel van Vugt (vanvugt)]

Seems to be fixed now using full KMS. Full KMS required both:

  * Kernel >= 5.10.7
  * Bug 1918110 to be fixed, which it now is.

[Daniel van Vugt (vanvugt)]

Also I am now using:

  dtoverlay=vc4-kms-v3d