Ubuntu Desktop freezing with Raspberry PI: the right way to repair

With the brand new Ubuntu Desktop 21.10 coming in manufacturing, I’ve discovered random freeze issues with my Raspberry PI 4 mannequin B laptop. After checks and googling the issue, I used to be in a position to remedy it

On this tutorial I’m going to indicate you the right way to repair the display freezing drawback with some Ubuntu Desktop kernels on Raspberry PI 4 / 400.

Raspberry PI 4 model B image

In keeping with https://bugs.launchpad.net/ubuntu/+source/linux-raspi/+bug/1946368, this can be a recognized bug on some Ubuntu kernel variations. Generally, this situation occurs when utilizing excessive decision screens (larger than 1920×1080@60Hz). Some customers report this situation additionally enjoying excessive decision movies and/or dragging functions to sidebar. Nevertheless, I discovered this drawback occurring in my Raspberry PI 4 mannequin B even when merely looking easy pages…

The problem comes from the default KMS, which seems to be unstable on Raspberry PI {hardware}. The workaround is enabling a “faux” KMS model, which limits the variety of features out there for video output however avoids freezing.

What's KMS (Kernel Mode-Setting)

As reported in Wikipedia, mode setting is a software program operation that prompts a show mode (display decision, shade depth, and refresh fee) for a pc’s show controller by utilizing VESA BIOS Extensions or UEFI Graphics extensions (on extra fashionable computer systems).

The show mode is about by the kernel.

In user-space mode-setting (UMS), a user-space course of units the show mode. Kernel mode-setting is extra versatile and permits displaying of an error within the case of a deadly system error within the kernel, even when utilizing a user-space show server. Person-space mode setting would require superuser privileges for direct {hardware} entry, so kernel-based mode setting shuns such requirement for the user-space graphics server.

Each Raspberry PI OS and Ubuntu use KMS.

Referring to a selected matter on Raspberry PI forum, the distinction between “vc4-fkms-v3d” and “vc4-kms-v3d” is the way it drives the video scaler (HVS), pixel valves, and output show blocks (HDMI/VEC/DSI/DPI).

  • With vc4-fkms-v3d this stays with the firmware, and the firmware nonetheless permits DispmanX or MMAL so as to add further layers.
  • With vc4-kms-v3d, the Linux kernel is driving all that lot, and DRM prohibits a number of shoppers including layers on the similar time.

Step-by-Step Process

From a terminal session in your Raspberry PI, open the config.txt file to edit:

sudo nano /boot/firmware/config.txt

Establish following line:


and alter it to:


Please word that new string merely provides a “f” char earlier than “kms”. Save and shut.

Reboot your OS and the problem must be fastened now.

Take pleasure in!

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