[Bug 89589] [dp mst] External displays remain blank with linux-3.18.6 after resuming from suspend

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=89589

--- Comment #16 from Konstantin A. Lepikhov <lakostis at altlinux.org> ---
I'm having this issue too - it never worked for me, so guess it could be
unrelated but still configuration is nearly the same:

- GPU: Haswell
- Laptop: DELL Latitude E5440
- MST dock from DELL
- 2 DELL U2415 monitors attached via mDP (DP1.2 disabled)

$ rpm -qa|fgrep xorg-x11-drv-intel
xorg-x11-drv-intel-2.99.917-16.20150729.fc23.x86_64

$ rpm -qa|fgrep xorg-x11-server
xorg-x11-server-common-1.18.0-0.4.20150907.fc23.x86_64
xorg-x11-server-Xorg-1.18.0-0.4.20150907.fc23.x86_64
xorg-x11-server-utils-7.7-16.fc23.x86_64

There are 2 monitors connected + eDP on laptop. When I boot the system
everything works just fine, monitors are visible and configurable via xrandr.
But if I suspend/resume the laptop, both monitors are in power save mode but
xrandr still show that they are connected. If I try to switch them off/on one
by one using xrandr but only one monitor start to work, another remain blank.

Attaching dmesg with drm debug enabled after resume and after play with xrandr.

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