How to set NoAccel to disable i915 GPU from Xorg.conf (to avoid GPU hang)

Question

I'm running Ubuntu on a new system with a GPU that uses the i915 kernel module. Unfortunately several times a week the gui crashes and dumps me to a terminal. journalctl shows the problem is:

kernel: i915 0000:00:02.0: [drm] GPU HANG: ecode 12:1:859fddff, in budgie-wm

I'm working on diagnosing the problem, but that's not my question today. Today I simply want to disable Xorg from using the GPU at all, so I can use Xorg without crashing. (I tried kernel parameter nomodeset which indeed disabled the GPU but then I couldn't even dim the screen backlight, so that's too extreme of a method for me. This is why I'm now looking at the Xorg layer.)

I read from the ArchLinux wiki that sometimes GPU hanging can be solved by setting Option "NoAccel" "True" in Xorg.conf. That's what I want to try.

There's some missing explanation, however. I think I should add this by creating a file under /etc/X11/xorg.conf.d/90-noaccel.conf. man xorg.conf explains that xorg.conf is organized into sections. What section should NoAccel go in? Maybe it should go in the Device section, but does that mean I have to put other lines in the same section to identify the device? And how can I tell whether NoAccel is recognized successfully in Xorg?

Answer 1

It is under device section. From X11R7.7 manpae

Section "Device"
Identifier "devname"
Driver "intel"   
...
EndSection

The option is

Option "NoAccel" "boolean"

Disable or enable acceleration.

Default: acceleration is enabled.

For some reason Arch manpage doesn't mention it. Instead it mention this (which can be found in previous one too)

Option "Accel" "boolean"

Enable or disable acceleration.
Default: acceleration is enabled.

Put the configuration in a xorg.conf file. /etc/X11/xorg.conf.d/99-disableacc.conf, put the device section.