[Bug 88620] New: [BSW partly bisected] testdisplay shows abnormal

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=88620

            Bug ID: 88620
           Summary: [BSW partly bisected] testdisplay shows abnormal
           Product: DRI
           Version: unspecified
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: jeff.zheng at intel.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 112531
  --> https://bugs.freedesktop.org/attachment.cgi?id=112531&action=edit
testdisplay -a output

==System Environment==
--------------------------
BIOS version V53
Regression: Yes. I tried _drm-intel-testing 2014_12_06 commit and testdisplay
shows normal. 

Non-working platforms: BSW

==kernel==
--------------------------
-testing: 2015_01_18 commit 6dd5bb25ce0ed3a0012b69d553d74e1a0d39c313(test
fails)


==Bug detailed description==
-----------------------------
Boot BSW, login and run testdisplay, eDP screen shows abnormal sometimes
testdisplay -a, or -d 24 will show abnormal. HDMI and DP screen also some
similar abnormal behavior.

The reproducibility > 90%

==Reproduce steps==
---------------------------- 
1. Boot BSW, login and run testdisplay

==Bisect==
I tried to bisect, but unfortunately because of bug 87671, some commits cannot
be bisected, in which commits testdisplay will show black screen.

Bad commit: 9025452366e9a86f2e11292865d98430341005d1 : Revert "drm/i915:
Parsing LFP brightness control from VBT"
Good commit: d9d8e6b3c01386e5b39b70dc07156ff0e407d984: the commit before
"drm/i915: Parsing LFP brightness control from VBT"
testdisplay will show black screen with commits between these two commit,
including commit 371abae844ede392066bfc21202b2e40f4a654d1: "drm/i915: Parsing
LFP brightness control from VBT"

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