[Bug 91407] [SNB] switching monitor off and on breaks DP output

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=91407

--- Comment #5 from Jani Nikula <jani.nikula at intel.com> ---
(In reply to Anton Khirnov from comment #4)
> (In reply to Jani Nikula from comment #3)
> > Do I understand correctly that you have the machine hooked up to the same
> > monitor using both DP and HDMI?
> > 
> 
> Yes. I added the HDMI connection there just for re-enabling DP because of
> this problem, otherwise I don't use it since it doesn't support my monitor's
> full resolution.
> 
> > The symptoms do sound like your userspace is not fancy enough to handle the
> > hotplug uevents. What to do on hotplug (or hot-unplug, or switching the sink
> > on/off) is a userspace policy decision. I'm guessing the driver keeps
> > transmitting the signal even after you've switched off the display, your
> > userspace does nothing, and when you switch the display back on, HDMI has a
> > fighting chance to recover, however the DP link doesn't recover like that.
> 
> Well, before kernel 3.18 my setup worked just fine without any fancy
> userspace hotplug handlers.

I wonder how that is possible for DP. The DP link goes down when you switch the
display off. We never automatically trained the link on hotplugging.

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