Created attachment 24102 [details]
Screenshot of garbled desktop

For a while I've had screen corruption on LVDS when I didn't use KMS and had tiling on. I mostly used external VGA connector and had no corruption in there, so I didn't care very much about this issue. The corruption doesn't occur when I either turn off tiling or switch to KMS.

However, a recent fences patch by Jesse Barnes made the issue mostly go away, with corruption remaining only in a few places. Before this patch the screen was totally garbled, but now it's only garbled a little bit. Details can be seen in attached screenshot.

The patch that changed the situation was:

commit 636d252f3b1eac687f7b11952e949c383cb86ed4
Author: Jesse Barnes <jbarnes@nietzche.localdomain>
Date:   Thu Mar 19 13:25:29 2009 -0700

    Don't install fences if the kernel is managing them


I have i855GM, using latest xf86-video-intel git, mesa 7.3, libdrm 2.4.5 and 2.6.29-rc8 kernel.

From xorg log:

(II) intel(0): [DRI2] Setup complete
(**) intel(0): Framebuffer compression enabled
(**) intel(0): Tiling enabled
(==) intel(0): VideoRam: 131072 KB
(II) intel(0): Attempting memory allocation with tiled buffers.
(WW) intel(0): xf86AllocateGARTMemory: allocation of 1536 pages failed
        (Cannot allocate memory)
(WW) intel(0): Allocation error, framebuffer compression disabled
(WW) intel(0): xf86AllocateGARTMemory: allocation of 10 pages failed
        (Cannot allocate memory)
(II) intel(0): Tiled allocation successful.