[Bug 107446] Monitor on 2nd DisplayPort is not initialized

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=107446

--- Comment #12 from Cedric M <cedric at maion.com> ---
Hi,

I believe I have this bug here with my setup.
Dell XPS 9343 (Broadwell i7-5600U) with an Dell P2715Q external monitor.

Worked fine on Ubuntu 18.04 (kernel 4.15), but since Ubuntu 18.10 (kernel
4.18), the external screen doesn't wake up after a period of inactivity:

- leave the laptop idle for a while, gnome screen lock will take over and shut
down the internal panel & external screen (it enters power saving mode). Same
behaviour as 18.04.

- however, if I come back after an hour or so and move the mouse or press a
key, only the internal panel wakes up. The external screen remains blank (Xorg
probably think that the external screen is on as the password prompt of gnome
screen lock will not be visible on the internal panel, it's probably displayed
on the blank surface -- I have to enter my password blind to get back to the
desktop).

Running xrandr without any argument sometimes helps getting the external screen
to turn on.
If I press a button on the monitor, it tells that it doesn't receive any
signal.
Switching it's input from it's usual DP input to another one, and switching
back again does restore the image.
Turning the monitor OFF and ON again also bring the content back.

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