Bug 108520

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.

Created attachment 142160 [details]
dmesg

Created attachment 142161 [details]
xorg log

(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

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?

(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.

(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.

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?

(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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