Created attachment 115108 [details]
Example of missing letters 1
Dear Intel graphic Team, Chris,
Copied from a Ubuntu bug report at:
As the issue doesn't looks like others, please find attached some screenshots.
A workaround is to enable UXA instead of SNA. Tested with last drivers from 01.org.
Created attachment 115109 [details]
Example of missing letters 2
Fixed several months ago in upstream, I even warned ubuntu about the bug...
Thank you Chris for your response; Now I have to convince someone from Ubuntu.
Do you remember the bug ID?
I informed tjaalton on irc about which patches he was missing...
In particular you need commit 7a9bdadd71730adc5266bc6758982abec5917b93
Author: Chris Wilson <firstname.lastname@example.org>
Date: Wed Oct 22 19:31:10 2014 +0100
sna/gen8: Clamp URB allocations for GT3
Does that patch apply to the HD Graphics 5500 (GT2) as well? I'm seeing the same issue running on Ubuntu 15.04. I downloaded the source package for the Intel drivers I'm currently running, and I'm seeing that patch already applied.
Just check upstream first, if you still have issues you have an entirely different bug.
FWIW, I tested the driver as of commit 4fdd3a7 and was still seeing the same issues. Turns out if I run a glx program (e.g. compton), I can't reproduce the issue. I also use awesomewm which doesn't come with a compositing window manager, however I noticed that I wasn't able to reproduce the issue with Unity or Gnome which both do include compositing window managers. The other thing I noticed is that if I didn't use a compositing window manager but opened glxgears after the screen corruption, the screen would be restored to normal.
That sounds more like a different kernel bug if a pageflip is flushing the scanout.