[Bug 89554] New: [SKL Bisected] eDP can not be lighted up after entering kernel

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=89554

            Bug ID: 89554
           Summary: [SKL Bisected] eDP can not be lighted up after
                    entering kernel
           Product: DRI
           Version: unspecified
          Hardware: All
                OS: Linux (All)
            Status: NEW
          Severity: critical
          Priority: highest
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: yex.tian at intel.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 114247
  --> https://bugs.freedesktop.org/attachment.cgi?id=114247&action=edit
dmesg with drm.debug info

System Environment:       
-----------------------------------------------------
Platform: SKL with new version CPU
Regression: Yes

==Kernel==
--------------------------------------------------
commit 3c0401df292f3cdf60435342a05bee3efb099ca0
Author: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira at intel.com>
Date:   Wed Mar 11 13:35:43 2015 +0200

    drm/i915: Simplify the way BC bifurcation state consistency is kept


Bug detailed description:
--------------------------------------------------
Edp display show blank screen with backlight is ON after entering kernel, while
SSH still working.
If connect mini-DP, mini-DP can display normally.

It’s kernel regression, Bisect shows the first bad commit is
(next-queued)7ad14a29f005.

commit 7ad14a29f0051ba4b631fb8ab3013e4577ffee95
Author:     Sonika Jindal <sonika.jindal at intel.com>
AuthorDate: Wed Feb 25 10:29:12 2015 +0530
Commit:     Daniel Vetter <daniel.vetter at ffwll.ch>
CommitDate: Wed Feb 25 16:06:42 2015 +0100

    drm/i915/skl: Add support for edp1.4 low vswing

    Based upon vbt's vswing preemph settings value select the appropriate
    translations for edp.


Please see the dmesg info.

Reproduce steps:
----------------------------
1, Boot up system with edp display connected

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