[Bug 93578] Intel HD 520 failed to train DP when connected with a external monitor

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=93578

--- Comment #8 from Oliver Deppert <Oliver.Deppert at gmail.com> ---
Hi all,

same problem here. I have a Dell XPS 15 9550 (late 2015 model, latest Feb 2016
bios version). Gentoo system with kernel 4.4.0-gentoo-r1. Currently I'm using
the iGPU config, so no "optimus" for the dCPU nvidia. Just the i915 kernel
driver with modesetting.

I have attached one HDMI monitor directly to the notebook (works), the second
one is connected via HDMI over USB-C/Thunderbolt adapter Dell DA200 (doesn't
work).

The second monitor is detected correctly, but as soon as I plug in the monitor
I got a lot of kernel messages (see attachment). 

So, while switching between different resolutions in XFCE monitor settings,
sometimes the second external HDMI monitor comes to life. e.g. 1024x768 works
and shows an image. 1920x1080 (the native resolution of the screen) doesn't
work. But with 1920x1080 at 30Hz it again shows up a screen, flickering but at
least showing something....same resolution but with 60Hz doesn't work.

I have attached the output of xrandr output for the "working" setup of
1920x1080 at 30Hz as well as for non-working 1920x1080 at 60Hz....unfortunatelly,
both show the same "settings"...no difference at all. Additionally, the
screenshot of the xfce screen setiings are attached...

with kind regards,
Oliver Deppert

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