[gentoo-user] Intel i915 sudden glitches

[Florian Philipp]

Hello list!

For a few days now I have issues with my i915 (GMA HD) graphics. Without
apparent reason (system load or whatever) everything except the mouse
pointer and audio freezes. After a few seconds it recovers but KDE
deactivates Composite. After that the system stays slow, watching videos
is impossible and some colors in some windows change.

dmesg is flooded with this after it happens:
drm:i915_do_wait_request] *ERROR* i915_do_wait_request returns -5
(awaiting 14302282 at 14260145)
[drm:init_ring_common] *ERROR* render ring head not reset to zero ctl
00000800 head 3241b08d tail 00000000 start 02001000
[drm:init_ring_common] *ERROR* render ring head forced to zero ctl
00000800 head 3241b08d tail 00000000 start 02001000
[drm:init_ring_common] *ERROR* render ring initialization failed ctl
0001f801 head 3241b08d tail 00000000 start 02001000

I did not change anything on the kernel (2.6.36-gentoo-r5 #3 SMP Sat Dec
25 19:00:13 CET 2010 x86_64 Intel(R) Core(TM) i5 CPU M 450 @ 2.40GHz).
The last change was the recent minor KDE update.

Sometimes I also notice that when I quickly flip between virtual
desktops, the rendering of windows gets messed up until a partial or
complete redraw happens after some event (mouse-over or resizing).

And just to throw in another symptome, sometimes GTK applications start
to mess up characters by randomly sustituting them. For example, last
time every occurence of "1" was rendered as "i". It only affects a few
characters but always different ones. I think this started after a
recent update to x11-libs/pango-1.28.3-r1.

My first guess is the turbo boost feature of these graphics chips but I
find it odd that it suddenly appeared after using this for months.

Does someone else experience the same or have a clue about the reason?

Thanks in advance!
Florian Philipp