Nouveau - Oct 2018 - [Bug 108520] New: MST DisplayPort HiDPI screen flicker

https://bugs.freedesktop.org/show_bug.cgi?id=108520

            Bug ID: 108520
           Summary: MST DisplayPort HiDPI screen flicker
           Product: xorg
           Version: unspecified
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Driver/nouveau
          Assignee: nouveau at lists.freedesktop.org
          Reporter: jhnmlkvch9 at gmail.com
        QA Contact: xorg-team at lists.x.org

HiDPI MST monitor connected via DisplayPort has bad screen flicker (one to
three high speed flickers every 20 seconds or so).

Version of X: 1.20
Nouveau: 1.0.15-3
Kernel: 4.18.16-arch1-1-ARCH

Curiously, the flicker only happens on my Optimus laptop with Hybrid Graphics
disabled (Intel off, Nouveau on). The flicker disappears if Hybrid Graphics is
enabled (Both Intel and Nouveau cards on).

Can't find anything relevant in dmesg, journal etc., but let me know which
logs
will be useful and I can upload them.

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--- Comment #1 from Ilia Mirkin <imirkin at alum.mit.edu> ---
I'd guess that in hybrid mode, the DP port is driven by Intel, which has a
more
battle-tested implementation.

dmesg and xorg log will be useful to provide background information, even if
they don't have any errors in them.

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--- Comment #2 from JM9 <jhnmlkvch9 at gmail.com> ---
Created attachment 142160
  --> https://bugs.freedesktop.org/attachment.cgi?id=142160&action=edit
dmesg

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--- Comment #3 from JM9 <jhnmlkvch9 at gmail.com> ---
Created attachment 142161
  --> https://bugs.freedesktop.org/attachment.cgi?id=142161&action=edit
xorg log

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--- Comment #4 from JM9 <jhnmlkvch9 at gmail.com> ---
(In reply to Ilia Mirkin from comment #1)
> I'd guess that in hybrid mode, the DP port is driven by Intel, which
has a
> more battle-tested implementation.
> 
> dmesg and xorg log will be useful to provide background information, even
if
> they don't have any errors in them.
attached xorg log and dmesg

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Ilia Mirkin <imirkin at alum.mit.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|MST DisplayPort HiDPI       |[GK104] MST DisplayPort
                   |screen flicker              |HiDPI screen flicker

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--- Comment #5 from Ilia Mirkin <imirkin at alum.mit.edu> ---
OK, so ...

A few facts:

 - GK104
 - Driving 4 monitors

Question: Are the 2560x1440 and 1920x1200 daisy-chained (hence the
"MST"
reference), or is it just that the 2560x1440 monitor's manufacturer name is
"MST", without any reference to Multi-Stream Transport?

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--- Comment #6 from JM9 <jhnmlkvch9 at gmail.com> ---
(In reply to Ilia Mirkin from comment #5)
> OK, so ...
> 
> A few facts:
> 
>  - GK104
>  - Driving 4 monitors
> 
> Question: Are the 2560x1440 and 1920x1200 daisy-chained (hence the
"MST"
> reference), or is it just that the 2560x1440 monitor's manufacturer
name is
> "MST", without any reference to Multi-Stream Transport?
They are not daisy-chained. I'm not sure about the MST reference. I think
this
is  a regression in X11 1.20. I filed a separate bug about that:
https://bugzilla.freedesktop.org/show_bug.cgi?id=108516
(If Hybrid Graphics is enabled, MST reference is gone.)

Another odd thing I noticed is, if I start X and then hot plug the monitor,
there is no flicker.

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--- Comment #7 from JM9 <jhnmlkvch9 at gmail.com> ---
(In reply to JM9 from comment #6)
> (In reply to Ilia Mirkin from comment #5)
> > OK, so ...
> > 
> > A few facts:
> > 
> >  - GK104
> >  - Driving 4 monitors
> > 
> > Question: Are the 2560x1440 and 1920x1200 daisy-chained (hence the
"MST"
> > reference), or is it just that the 2560x1440 monitor's
manufacturer name is
> > "MST", without any reference to Multi-Stream Transport?
> 
> They are not daisy-chained. I'm not sure about the MST reference. I
think
> this is  a regression in X11 1.20. I filed a separate bug about that:
> https://bugzilla.freedesktop.org/show_bug.cgi?id=108516
> (If Hybrid Graphics is enabled, MST reference is gone.)
> 
Scratch that. I was being confused. The MST reference is still there, but the
naming scheme is different.
> Another odd thing I noticed is, if I start X and then hot plug the monitor,
> there is no flicker.
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--- Comment #8 from Ilia Mirkin <imirkin at alum.mit.edu> ---
So it sounds like there's a DP ports are hard-attached to the NVIDIA chip,
which is why you're seeing it as "DP-1-1" for the
"optimus" case. It's actually
using the outputs attached to the NVIDIA gpu. The "local" DP outputs
are
probably meant for a dock.

Are both the 2560x1440 and 1920x1200 monitors attached via DP? Or are there
converters in between?

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--- Comment #9 from JM9 <jhnmlkvch9 at gmail.com> ---
(In reply to Ilia Mirkin from comment #8)
> So it sounds like there's a DP ports are hard-attached to the NVIDIA
chip,
> which is why you're seeing it as "DP-1-1" for the
"optimus" case. It's
> actually using the outputs attached to the NVIDIA gpu. The
"local" DP
> outputs are probably meant for a dock.
> 
> Are both the 2560x1440 and 1920x1200 monitors attached via DP? Or are there
> converters in between?
They are both connected via dock. 2560x1440 (the only one with the flicker
problem) is additionally going through a DP to DVI Dual Link Adapter.

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Martin Peres <martin.peres at free.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |MOVED
             Status|NEW                         |RESOLVED

--- Comment #10 from Martin Peres <martin.peres at free.fr> ---
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