[Nouveau] [Bug 101559] New: Displays fail to wake up when booting machine away from Display Port KVM switch

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=101559

            Bug ID: 101559
           Summary: Displays fail to wake up when booting machine away
                    from Display Port KVM switch
           Product: xorg
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Driver/nouveau
          Assignee: nouveau at lists.freedesktop.org
          Reporter: dhruv.a.thakkar at leidos.com
        QA Contact: xorg-team at lists.x.org

Created attachment 132142
  --> https://bugs.freedesktop.org/attachment.cgi?id=132142&action=edit
Xorg.0.log

Description of problem:

We are trying to solve an issue in which displays fail to wake up when booting
a Rhel 7.3 machine (Machine A) connected to a Display Port KVM while the KVM is
pointing to Machine B. The unusual bit is that xorg logs in /var/log/Xorg.0.log
indicate that everything comes up correctly, and a "ps -ef |grep X|xinit" shows
that X and xinit are up and running. If we boot Machine A while the KVM is
pointing to it, the displays come up with no issues.

We have KMS parameters set to force the output of the video
(video=DP-1:2560x1600D and video=DP-2:2560x1600D) as well as options to load
the EDID information. These parameters have worked in the past for us when we
used DVI connections through KVMs, but DisplayPort is not showing the same
results. Note that we have additional kernel options added for extra debug
information (log_buf_len=8M nouveau.debug=disp=trace,i2c=trace,bios=trace)

Using Xrandr and Udev rules with a script allow us to turn off and then back on
the displays automatically, allowing us a workaround, but it still does not
solve the core issue of that nouveau is not waking up the monitors.

Please see the attached logs/config files and diagram below for more
information.

|Machine A| |Machine B|
\               /
 \             /
  \ _________ /
   |DPort KVM|
   |_________|
   /         \
  /           \
 /             \
|Monitor 2| |Monitor 1|

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