[Bug 88081] New: [BSW Bisected]Display show black screen when starting gnome-session

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=88081

            Bug ID: 88081
           Summary: [BSW Bisected]Display show black screen when starting
                    gnome-session
           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: wendy.wang at intel.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 111803
  --> https://bugs.freedesktop.org/attachment.cgi?id=111803&action=edit
dmesg-gnome-blank

System Environment:
--------------------------
Platform: BSW
OS Distribution: Ubuntu 14.04
Kernel regression:
 both latest drm-intel-nightly (07d0c831d9207c937595f081c8fddbddbf53756f)
and drm-intel-next-queued branch fail 


Kernel Regression:
--------------------------
Yes, bisected on drm-intel-next-queued branch:

371abae844ede392066bfc21202b2e40f4a654d1 is the first bad commit
commit 371abae844ede392066bfc21202b2e40f4a654d1
Author: Deepak M <m.deepak at intel.com>
Date:   Mon Dec 15 15:58:21 2014 +0530
Commit:     Daniel Vetter <daniel.vetter at ffwll.ch>
CommitDate: Mon Dec 15 11:25:29 2014 +0100

    drm/i915: Parsing LFP brightness control from VBT

    LFP brighness control from the VBT block 43 indicates which
    controller is used for brightness.
    LFP1 brightness control method:
    Bit 7-4 = This field controller number of the brightnes controller.
    0 = Controller 0
    1 = Controller 1
    2 = Controller 2
    3 = Controller 3
    Others = Reserved
    Bits 3-0 = This field specifies the brightness control pin to be used on
the
    platform.
    0 = PMIC pin is used for brightness control
    1 = LPSS PWM is used for brightness control
    2 = Display DDI is used for brightness control
    3 = CABC method to control brightness
    Others = Reserved

    Adding the above fields in dev_priv->vbt and corresponding changes in
    parse_backlight()

    v2: Jani's review comments addressed
        - Move PWM definitions to intel_bios.h
        - Moving vbt_version to intel_vbt_data
        - Rename brightness to bl_ctrl_data
        - Logging just control_pin instead of string
        - Avoid adding vbt_version in dev_priv
        - Since only DDI option is available as of now, let control pin DDI
        affect dev_priv->vbt.backlight.present

    v3: Jani's review comments addressed
        - Drop control_pin
        - Use bdb->version
        - set controller to 0 instead of using control pin define
        - check controller bounds
        - remove superfluous changes in intel_parse_bios

    Signed-off-by: Deepak M <m.deepak at intel.com>
    Signed-off-by: Vandana Kannan <vandana.kannan at intel.com>
    Reviewed-by: Jani Nikula <jani.nikula at intel.com>
    Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>

:040000 040000 1a70f7733307b3dc8545fae58760d314f59f1087
75ec00642c7ee92fda81d0a2f0d74971f8a90164 M      drivers



Reproduce steps:
1. boot into system
2. xinit &
3. screen
4. gnome-session &
will observe display show black screen when starting gnome-session.

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