[Bug 74381] New: ASUS T100TA panel video cannot be reenabled after it is disabled

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=74381

            Bug ID: 74381
           Summary: ASUS T100TA panel video cannot be reenabled after it
                    is disabled
           Product: Drivers
           Version: 2.5
    Kernel Version: 3.15.0_rc1
          Hardware: x86-64
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Video(DRI - Intel)
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: rhowell at uwyo.edu
                CC: intel-gfx-bugs at lists.freedesktop.org
        Regression: No

Starting approximately with the merge of the new i915 code into the 3.15 kernel
about April 8, the panel video on my ASUS T100A cannot be renabled once it has
been disabled, until the system is rebooted.

The panel display and an external HDMI display come up properly on boot, but if
I do anything to turn off the panel display, such as "xrandr --output VGA1
--off", then nothing I do after that is able to make the panel display visible
till I reboot.  After an "xrandr --output VGA1 --auto" the system seems to
THINK the panel is active, as indicated by xrandr output and also the implied
limits of the display when moving windows and the mouse from one display to the
other, but there just isn't any visible panel output.  The HDMI is fine.  I
don't see any error messages in any of the logs.  The system really acts like
some part of the video output chain has been disabled, but never gets reenabled
till a reboot.

Running the 3.14 kernel and versions of the partly merged 3.15 kernel before
approximately April 8, I am able to turn off then turn on the panel.  For your
information, I've compiled this as x86_64, am using the video=VGA-1:1368x768e
parameter at boot, and also specify an edid file I created, as the display is
otherwise scrambled.

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