[Bug 99362] New: no resolutions >=1080p with Acer P7500 and Thinkpad X1

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=99362

            Bug ID: 99362
           Summary: no resolutions >=1080p with Acer P7500 and Thinkpad X1
           Product: DRI
           Version: DRI git
          Hardware: Other
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: m.heide at tarent.de
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Hardware: Thinkpad X1 1294-2NG and Acer P7500 (projector) 

With Ubuntu 14.04 everything is fine. 

Updating to Ubuntu 16.04 and by default the connected projector says: no
signal. With other external monitors everything is fine, it's just the
projector which doesn't like the default resolution 1080p. 

Using lower resolutions and/or timings like 1024x768 or 1920x1080i (25Hz,
interlaced 50Hz) everything is fine. 

I tried several modelines and all manually calculated modelines like with gtf
or other tools do not work even on Ubuntu 14.04. It's just the default
recognized (DDC?) modeline with Kernels <=4.2 that work. 

Using Ubuntu 16.04 i tried different kernels:

successfully:
* all official kernels coming with Ubuntu 14.04
  (i.e. using kernel 3.19 with Ubuntu 16.04 works)
* from http://kernel.ubuntu.com/~kernel-ppa/mainline/
 - v4.2.8-ckt13 
 - v4.3-rc1 with drivers/gpu/drm/i915 directory from v4.2.8-ckt13
* from git clone git://anongit.freedesktop.org/git/drm-tip
 - git checkout f8896f5d58e64bfd3c2b5f7c5ba5c3f3967e93c7

broken:
* all official kernels coming with Ubuntu 16.04 
  (i.e. using kernel 4.4 with Ubuntu 14.04 doesn't work)
* from http://kernel.ubuntu.com/~kernel-ppa/mainline/
 - v4.3-rc1 unmodified
* from git clone git://anongit.freedesktop.org/git/drm-tip
 - git checkout ca6e4405779ed56ebac941570615abd667c72c02

So I think the regression must be added between
f8896f5d58e64bfd3c2b5f7c5ba5c3f3967e93c7 and
ca6e4405779ed56ebac941570615abd667c72c02. 
I.e. between DRIVER_DATE 20150522 and 20150731. 

(I've copied the i915-directory from Kernel v4.2.8-ckt13 to Kernel  v4.3-rc1,
fixed some incompatibilities to successfully compile the kernel and this works.
So it's something inside i915 which causes this behaviour.)

Still digging further into it...

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