[REGRESSION] i915: failure to see Dell 30" monitor connected to a Lenovo Haswell docking station

[Theodore Ts'o]

On Tue, Sep 02, 2014 at 02:15:39PM +1000, Dave Airlie wrote:
> On 2 September 2014 14:05, Theodore Ts'o <tytso at mit.edu> wrote:
> > I recently upgraded to v3.17-rc3, and on my Lenovo T540p, I can no
> > longer see the my Dell 30" monitor when it is connected via the
> > docking station using a Displayport connector.  This worked using 3.16
> > kernel.
> >
> > If I connect to the monitor using the mini-display, by passing the
> > docking station, things work fine (but of course it's annoying not to
> > be able to use the docking station).
> >
> > Is this a known problem?  This is not the first time that we've had
> > regressions with this docking station.   It's vaguely reminsicent of
> >
> >         https://bugs.freedesktop.org/show_bug.cgi?id=71267
> >
> > Except the system isn't hanging; it's just not seeing the monitor at all.
> 
> Have you the Dell 30" set to Displayport 1.2 enabled mode?
> 
> If so, then see if disabling that in the monitor menus helps.
> 
> This is probably due to the fact we now attempt to talk to new DP devices
> with the protocol they provide. So previously the monitor exposed DP 1.2
> and we just didn't care, now if it exposes it we attempt to talk to it.

Hi Dave,

I've since upgraded to a newer X server, which may have been
responsible for the symptoms somewhat.  It now doesn't seem to matter
whether the Dell 30" monitor is set to DP 1.2 or not.  It now will
find the Dell 30" monitor reliably when the system is freshly booted,
attached to the Dock.  If I then suspend the laptop, remove it from
the dock, unsuspend it from the laptop, then resuspend the laptop, and
return it to the dock, it can no longer see the monitor until I
reboot.

I am currently running 3.17-rc4 based kernel, and I have the following
X server components:

ii  xserver-xorg                    1:7.7+7              amd64                X.Org X server
ii  xserver-xorg-core               2:1.16.0.901-1       amd64                Xorg X server - core server
ii  xserver-xorg-video-intel        2:2.21.15-2+b2       amd64                X.Org X server -- Intel i8xx, i9xx display driver

Here is the dmesg file with drm.debug=6.  Could you take a quick look
and see if anything obvious jumps out at you?

Thanks,

						- Ted

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