[Bug 15186] New: Radeon KMS: [RV730] Garbled kwin shadows and pixmaps

[bugzilla-daemon@bugzilla.kernel.org]

http://bugzilla.kernel.org/show_bug.cgi?id=15186

           Summary: Radeon KMS: [RV730] Garbled kwin shadows and pixmaps
           Product: Drivers
           Version: 2.5
    Kernel Version: 2.6.33-rc4
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - non Intel)
        AssignedTo: drivers_video-dri@kernel-bugs.osdl.org
        ReportedBy: r.schedel@yahoo.de
        Regression: Yes


Created an attachment (id=24816)
 --> (http://bugzilla.kernel.org/attachment.cgi?id=24816)
Xserver log

Since 2.6.33-rc4 up to rc6 I randomly have garbled kwin shadows, either blue or
yellow frames around the window shadows.
In kernels 2.6.32 and <=2.6.33-rc3 this was not observable (=regression).

Also described here by someone else:
http://bbs.archlinux.org/viewtopic.php?pid=690047#p690047

The effect happens randomly when switching between windows. However, it is also
100% reproducable for me by the command
  x11perf -create
After this the window has a white shadow frame (see screenshot). The window
entry in the taskbar is sometimes garbled with a white pixmap too (see
screenshot).

If running with kwin composite *disabled*, only the white pixmap is observed --
as window shadow effects are disabled.

Kernel log or xserver log do not provide any useful hints.

Bisecting the git kernel shows this as culprit:
> [c07d7237a639d57dc91ea7efdbc1b3f85c7a095d] Merge branch 'drm-linus' of
> git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6
> c07d7237a639d57dc91ea7efdbc1b3f85c7a095d is the first bad commit

Bisecting branch "drm-linus" further showed this culprit:
> cafe6609d6dc0a6a278f9fdbb59ce4d761a35ddd is the first bad commit
> commit cafe6609d6dc0a6a278f9fdbb59ce4d761a35ddd
> Author: Jerome Glisse <jglisse@redhat.com>
> Date:   Thu Jan 7 12:39:21 2010 +0100
>
> drm/radeon/kms: Schedule host path read cache flush through the ring V2

After reverting this patch on 2.6.33-rc6, the issue was resolved on my hardware
configuration. However, I am unsure about the internals of this commit.

Information hopefully is sufficient for an expert to track this further.

Environment:
Linux 2.6.33-rc4..6 with Radeon KMS ("modprobe radeon modeset=1")
Mesa master branch
xf86-video-ati master branch
Xorg server 1.7.4
libdrm 2.4.17 (or master too)
KDE 4.3.95 (composite desktop enabled or disabled, see above)

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