[Bug 93578] [SKL] Intel HD 520 failed to train DP when connected with a external monitor

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=93578

--- Comment #101 from Mads <mads at ab3.no> ---
(In reply to Mads from comment #100)
> (In reply to Mads from comment #95)
> > Tested DP MST with a fresh drm-tip today (commit
> > 0a03ea9496b49746b4964d05cc1f483385d1df8a), and it seems like daisy chaining
> > triggers the same kind of behaviour as with the DA200 dongle, so maybe the
> > error is related.
> > 
> > When Daisy chaining two Dell U2715H monitors through DisplayPort, the last
> > monitor in the chain cannot get a resolution higher than the range
> > previously mentioned here (1024x768 works, 1600x1200 does not, 1920x1080
> > does not).
> 
> It just dawned on me that I tested this through a Dell WD15 docking, maybe
> DP MST works if you don't use that (maybe the WD15 got the same data link
> issue as DA200).
> 
> I got a standard non-Dell USB-C to DP dongle that I know works with 4k @
> 60Hz, I can try if DP MST works with that on monday.

My suspicions were correct, with a standard non-dell USB-C to DP dongle, DP MST
works like a charm. Writing this reply with two Dell U2715H monitors connected,
both with 2560x1440 at 60Hz.

So, making DA200 work with Linux might fix lots of docking issues :)

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