[Bug 111507] Unable to detect monitor modes connected to a TB16 Dell dock

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=111507

--- Comment #27 from Lionel Landwerlin <lionel.g.landwerlin at linux.intel.com> ---
(In reply to Stanislav Lisovskiy from comment #26)
> (In reply to Lionel Landwerlin from comment #25)
> > (In reply to Stanislav Lisovskiy from comment #23)
> > > (In reply to Lionel Landwerlin from comment #22)
> > > > (In reply to Stanislav Lisovskiy from comment #21)
> > > > > It is kernel command line, which can be edited same way as you add
> > > > > drm.debug=0x1e in grub.cfg, just add 3 after drm.debug, so that it looks
> > > > > like "drm.debug=0x1e 3". This will make it boot into console mode, without
> > > > > GUI, however if it works
> > > > > that way we will know at least whether this is GDM messing up things or some
> > > > > problem in the kernel.
> > > > 
> > > > I don't have a splash screen during the boot, so before GDM starts, I can
> > > > see the console on both monitors. Is that what you wanted to know?
> > > 
> > > How about unplug/plug the display in the console mode? Does it work reliably?
> > 
> > Yep, works fine.
> 
> Please "Revert "drm/i915: Fix DP-MST crtc_mask" from Ville, most likely the
> issue is caused by this. Ville's change itself was correct as I understand
> however Mutter and some other userspace apps does some stuff like
> "intersecting" possible crtc mask which results to 0 after this change. For
> console as we checked it does it properly, which explains why you don't have
> it there.
> So please revert this change you had bisected to and check if that helps.

Like I wrote earlier, the bisect was wrong. Sometimes the monitor will manage
to work and that screwed up the bisect.

Reverting that one patch doesn't actually help.

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