[Intel-gfx] Is Skylake graphics completely broken with multiple monitors?

[Oskar Berggren]

2016-04-02 15:08 GMT+01:00 Oskar Berggren <oskar.berggren at gmail.com>:

> Hi,
>
> After trying two different machines I'm beginning to feel like Skylake is
> completely unusable with multiple monitors connected. Is this a known
> limitation? Am I the only one experiencing this?
>
> First I tested on laptop Dell XPS 15 9550 with QHD display. Seems to work
> fine with internal panel, though I haven't used it extensively. Immediately
> or sometimes within a minute or two when I connect an external monitor
> using HDMI the system freezes completely (ping reply stops). This is with
> updated Fedora 23 with kernel from drm-intel-nigthly tested several times
> during the last two months. I've reported this here:
> https://bugs.freedesktop.org/show_bug.cgi?id=94625 with more details.
>
>
> Now I've also got access to a Dell Precision Tower 3620. Being a tower,
> this of course has no internal panel. Connecting one external monitor seems
> to work, but again I've not used it extensively. The second I connect a
> second monitor it freezes completely. Booting with two monitors connected
> also doesn't work. This is with updated Fedora 23 and distribution kernel
> 4.4.6-300 (waiting for download/build of drm-intel-nigthly to finish). CPU
> is i7-6700 stepping 3 microcode 0x74.
>


More testing:

It turns out both systems are reasonably stable using Fedora's 4.4.6-300
kernel - on HDMI and DP _without _ MST. This is what caused the problem -
my DELL U2415 monitor with DP 1.2 enabled causes stability issues, system
freeezes, or is not detected at all, on 4.4.6 and drm-intel-nightly. HDMI
or DP 1.1 seems to work.

However, drm-intel-nightly from last night is still very unstable with HDMI
on the laptop, and also with DP 1.1 for external monitors on the tower
system.

/Oskar
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