[Intel-gfx] Corruption in glxgears with Compiz

[Peter Clifton]

On Fri, 2010-10-22 at 14:39 +0100, Chris Wilson wrote:
> On Fri, 22 Oct 2010 13:53:16 +0100, Peter Clifton <pcjc2 at cam.ac.uk> wrote:
> > Hi guys,	
> > 
> > I was wondering whether anyone has tried the latest stack of drivers
> > with compiz running?
> > 
> > I'm running the Ubuntu Xorg edgers PPA with a home-brew backport of
> > drm-intel-next against the 2.6.35 ubuntu kernel. That was working fine
> > until recently, but with compiz running I'm getting some visual
> > corruption. (I've attached a fragment of a screen-shot captured during
> > the problem).
> 
> Which commit did you take your backport from? There were a couple of
> pageflip related commits that I'm interested in knowing how they fare and
> QA has chastised me for introducing a couple of bugs as well.
> -chris

As an additional data-point, with the bug manifesting, if you go to
"expose" mode, (Win+E for default config), you find the corruption is
absent. It only appears to be present when the glxgears window is not
scaled by the window manager.

With (urgh) wobbly windows turned on, it is less manifest when the
window is being wobbled, but there is still some edge tearing and
corruption.

With drm debugging enabled (modprobe drm debug=2), I noticed some pipe
underrun errors in the logs. If you want further info, let me know. I
wasn't sure they were correlated to the problem though.

With glxgears running in the background, corruption isn't just
restricted to that window. For example, I have glxgears running in the
background now, and the email composer caret is being left behind some
times as I type. Similarly, on a console window (gnome terminal),
certain glyphs are rendering as blank, or full black. This goes away
when the window is re-exposed by dragging another window on top, so I
guess it is not the glyphs themselves which were corrupted.

Whilst I don't have nearly your level of expertise with the driver, I'm
keen to know what you're thinking these symptoms might point to, and
what you think is worth looking at to debug. I know you'll beat me to a
fix, but I'm curious as to how one even starts debug this kind of issue
(aside from bisection).

I just tried to build and run with a stock (ish) Ubuntu kernel (removed
the stgit series for my backport of agp and drm drivers), but I couldn't
log in (with compiz auto-starting), without the graphics freezing up.
Probably something else in the "new" stack needs a newer kernel driver I
guess.

Best regards,

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)
Tel: +44 (0)1223 748328 - (Shared lab phone, ask for me)