[Bug 89612] New: xrandr --off --> --auto fails to re-enable external (MST) monitors

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=89612

            Bug ID: 89612
           Summary: xrandr --off --> --auto fails to re-enable external
                    (MST) monitors
           Product: xorg
           Version: unspecified
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Driver/intel
          Assignee: chris at chris-wilson.co.uk
          Reporter: tim.besard at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org

Created attachment 114389
  --> https://bugs.freedesktop.org/attachment.cgi?id=114389&action=edit
dmesg after booting on 3.14 + MST patches, with drm.debug=14

I'm using Arch Linux (shipping xf86-video-intel 2.99.917 and xorg-server
1.17.1)
on my T440s with two external Dell 24" monitors connected over both DVI and DP
to a docking station. This specific docking station (official Ultra dock) uses
DP MST to wire the external connections.

When connected to the external displays, I'm not using my laptops screen (lid
closed). I'm configuring my external screens as follows:

$ xrandr --output DP2-2 --auto --output DP2-1 --auto --right-of DP2-2

If I disable my external screens using:

$ xrandr --output DP2-1 --off --output DP2-2 --off

... and I try to revive them afterwards using:

$ xrandr --output DP2-2 --auto --output DP2-1 --auto

xrandr responds with "Configure crtc 1 failed" and both my external screens
refuse to turn on.

I tested this on the 3.19 kernel Arch linux ships, as well as the initial 3.14
+
MST patches from Dave Airlie's git tree, but I'm seeing identical behaviour on
both kernels.

Attached are multiple files:

* dmesg.log: boot-up dmesg on 3.14 with drm.debug-14 (as per Fedora reporting
  guidelines)
* dmesg.xrandr.log: relevant drm debug statements from dmesg around the xrandr
  commands detailed above
* dri_*_i915_opregion, lspci.log, Xorg.0.log: as per Fedora's guidelines again
* reg_snapshot_*: register snapshots *before* doing anything (laptop screen
off,
  both external displays enabled), *after* issuing the "xrandr --off" (and
  opening my laptop screen in order to see something), and after trying "xrandr
  --auto" and seeing a *failed* message

Note that when I was recording the register snapshots above, and rebooting
after
nuking my external displays with "xrandr --off", I briefly got to see my init
system output on one of my external screens just before the system rebooted.

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