[Bug 13785] New: "drm/i915: add FIFO watermark support" breaks Fujitsu S7110 with SXGA+ display

[<bug...@bu...>]

http://bugzilla.kernel.org/show_bug.cgi?id=13785

           Summary: "drm/i915: add FIFO watermark support" breaks Fujitsu
                    S7110 with SXGA+ display
           Product: Drivers
           Version: 2.5
    Kernel Version: 2.6.31-rc2
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI)
        AssignedTo: dri...@ke...
        ReportedBy: bug...@mk...
                CC: sha...@in...
        Regression: Yes


Created an attachment (id=22377)
 --> (http://bugzilla.kernel.org/attachment.cgi?id=22377)
Xorg.log

The patch mentioned in the subject (commit
7662c8bd6545c12ac7b2b39e4554c3ba34789c50 in mainline) breaks the X server on
the Fujitsu S7110 with an SXGA+ display.

The X server still works and displays the correct image as long as no major
drawing activity takes place. As soon as something happens on the screen (even
scrolling in gnome-terminal), the image on the screen starts to jump around.
When the drawing is finished, everything looks fine again. Reverting the
mentioned patch helps.

https://bugs.freedesktop.org/show_bug.cgi?id=22264 might be related. I am
sorry, but I currently don't have the log file of the broken X server at hand,
so I can't check for underrun messages; yet the erratic display looks *VERY*
much like FIFO underruns.

I have the Xorg.log (running current HEAD kernel
35b5c55fee08e6e4001ba98060a2d0b82f70b5f4, but with
5aa8f839f8d96a65082456124fff1f16d4738586 and
c99f0b4fe83c0ed1efcfedcfdb2050b08a3c1a15 reverted) attached.

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