[Bug 54129] New: [bisected] Kernel 3.5.0 breaks KMS on Radeon RV250

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=54129

             Bug #: 54129
           Summary: [bisected] Kernel 3.5.0 breaks KMS on Radeon RV250
    Classification: Unclassified
           Product: DRI
           Version: unspecified
          Platform: x86 (IA32)
        OS/Version: Linux (All)
            Status: NEW
          Severity: major
          Priority: medium
         Component: DRM/Radeon
        AssignedTo: dri-devel at lists.freedesktop.org
        ReportedBy: mariofutire at googlemail.com


Created attachment 66187
  --> https://bugs.freedesktop.org/attachment.cgi?id=66187
Screenshot of bad rendering

I run Fedora 17 and since they have shipped a kernel 3.5.X I have a lot of
artefacts when I log in KDE.

Kernel 3.4.6 works ok.

My hardware in a Thinkpad laptop with a 

01:00.0 VGA compatible controller: ATI Technologies Inc Radeon RV250 [Mobility
FireGL 9000] (rev 02)

and I load the R200 microcode.

Basically, as soon as I log on KDE I have a lot of rectangular areas which are
left black.
They are 100% reproducible always with the same pattern (at least in the few
seconds before I logoff again), and they move around when I click or windows
are displayed.

If I pass the option radeon.modeset=0 to the kernel (in grub) there are no
artefacts, but of course XV support is not there so this is not really an
option as video player struggle a lot.

I managed to bisect the issue to the following commits:

bad ========= 3b7a2b2 drm/radeon: rework fence handling, drop fence list v7
skip ======== bb63556 drm/radeon: convert fence to uint64_t v4
good ======== d6999bc drm/radeon: replace the per ring mutex with a global one

"skip" here means that the kernel does not boot: after the linux penguin logo
is displayed on the top left of the screen, nothing else happens, even though I
am able to reboot pressing Ctrl-Alt-Del.

So there are 2 commits that could be responsible.

Please, let me know if there is anything I can provide on top of that.

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