[Bug 104807] New: blank screen after drm initialization - trekstor twin 10.1

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=104807

            Bug ID: 104807
           Summary: blank screen after drm initialization - trekstor twin
                    10.1
           Product: DRI
           Version: DRI git
          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: hexdump0815 at googlemail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 136985
  --> https://bugs.freedesktop.org/attachment.cgi?id=136985&action=edit
boot output with drm.debug=0x1e with drm enabled

hello,

for quite some time i'm trying to get drm working on a trekstor twin 10.1, a
baytrail (Intel(R) Atom(TM) CPU  Z3735F @ 1.33GHz) tablet, but during drm
initialization the screen goes blank. from the software side everything seems
to work well, as the xorg process is running and i can login blindly and see
the lxde session processes running - its just that the display does not show
anything. i got backlight control fully working via the dracut workaround from
https://bugs.freedesktop.org/show_bug.cgi?id=96571 - so the backlight is not
the problem. this is neither a duplicate of
https://bugs.freedesktop.org/show_bug.cgi?id=82880 - which fixed a very similar
problem on my dell venue pro 8, but does not help on this trekstor tablet (i
tried it with hans de goede's tree from yesterday).

i'll attach a full dmesg output with drm.debug=0x1e from drm-tip as of now (git
hash 59275f1cec1d31adab39ddb6ab948519ac8ddffb) - once with drm (where i get the
blank screen) and once running with nomodeset (where everything is running fine
- but without drm, which i would like to get running). please let me know, if
you need any more information to help getting this sorted out. i can compile
kernels easily, have ssh access to the machine when the screen is blank etc.
and can run more commands for debugging if needed. the os is lubuntu 17.10 btw.

a lot of thanks in advance and best wishes

thomas

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