[Bug 91614] New: DVI display on DisplayPort-MST behind DP-DVI converter gets no EDID

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=91614

            Bug ID: 91614
           Summary: DVI display on DisplayPort-MST behind DP-DVI converter
                    gets no EDID
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: cweiske at cweiske.de
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 117641
  --> https://bugs.freedesktop.org/attachment.cgi?id=117641&action=edit
dmesg with drm.debug=14

My setup: Thinkpad T440p with an Ultra Dock, two identical displays connected
to the dock. DP2-1 connected via a DP-DVI converter to the docks' display port
socket, DP2-2 connected directly to the dock's DVI port.

DP2-1 gets the wrong resolution; "xrandr --verbose" shows that no EDID data are
available. I can manually add the correct resolution with "xrandr --addmode",
which makes the display work on the correct resolution.

I can swap the displays physically, and the one connected to the DVI port
always gets the correct resolution - so it is not a display issue.

I connected the display via a MiniDP-DVI adapter directly to the laptop
(bypassing the docking station) and it got the correct resolution.


Attached is dmesg output with drm.debug=14


Xorg server: 1:7.7+1ubuntu8.1
xf86-video-intel: git 2015-07-31 17:17,
bc063c9f4af90542297877281b1b9f4692dafde4
Linux kernel: Linux csystems 4.1.4-dp-mst #1 SMP Fri Aug 7 09:25:36 CEST 2015
x86_64 x86_64 x86_64 GNU/Linux

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