[Bug 62275] New: [HSW 3.8.2 regression] After running testdisplay with only eDP, screen turn to black and can't light up again

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=62275

          Priority: medium
            Bug ID: 62275
          Assignee: intel-gfx-bugs at lists.freedesktop.org
           Summary: [HSW 3.8.2 regression] After running testdisplay with
                    only eDP, screen turn to black and can't light up
                    again
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
          Severity: critical
    Classification: Unclassified
                OS: All
          Reporter: yangweix.shui at intel.com
          Hardware: Other
            Status: NEW
           Version: unspecified
         Component: DRM/Intel
           Product: DRI

Description:
----------------------------------
It's a new regression of HSW on 3.8.2 kernel:
[19b00d2dc9bedf0856e366cb7b9c7733ded659e4] Linux 3.8.2

I find 3.8 kernel is good:
[19f949f52599ba7c3f67a5897ac6be14bfcb1200] Linux 3.8

Our machine is lent to other team for a period, I will attach the attachment
later.

Reproduce step:
----------------------------------
1. reboot with bad commit kernel
2. ./testdisplay
3. After display the mode, then screen turn to black and can't light up again

Bisect result:
----------------------------------
719429a54d9c8fd32d457c7d564d1272d9003282 is the first bad commit
commit 719429a54d9c8fd32d457c7d564d1272d9003282
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Wed Feb 6 11:24:41 2013 +0100

    drm/i915: write backlight harder

    commit cf0a6584aa6d382f802f2c3cacac23ccbccde0cd upstream.

    770c12312ad617172b1a65b911d3e6564fc5aca8 is the first bad commit
    commit 770c12312ad617172b1a65b911d3e6564fc5aca8
    Author: Takashi Iwai <tiwai at suse.de>
    Date:   Sat Aug 11 08:56:42 2012 +0200

        drm/i915: Fix blank panel at reopening lid

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