[Bug 94985] [HSW] Severe screen flickering on external monitor after i915.enable_psr=1

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=94985

--- Comment #11 from Leho Kraav (:macmaN :lkraav) <leho at kraav.com> ---
(In reply to Leho Kraav (:macmaN :lkraav) from comment #10)
> Yes, it's still there, but fortunately the problem has become much less
> severe over time.

(forgot above, monitor is DELL 3415W)

PS the confusing part of it is, the problem doesn't manifest with any
regularity for me. I play videos on the external screen very often and majority
of the time everything is fine. (PS dropping X and xf86-video-intel in favor of
pure wayland + mesa has produced a massive improvement in reducing video
stuttering in Firefox, and video performance/workflow stability in general)

Historically, back in earlier 4.x series, ever since enable_psr=1 landed
(4.5-4.6?), flickering was a regular guest even on the laptop eDP1 display.
That was soon after fixed, I haven't seen that happen for a long while now. 

External screen keeps on occasionally flickering. I think somewhere at 4.7-4.8+
this has also been reduced to bare minimum, where it only rarely disturbs
everyday workflow.

I'm not sure if also connected to this specific problem, or i915 drm layer in
general, but these are the quirks I'm still seeing in 4.9.0-rc6 (haven't had
time to upgrade to later, based on changelog not much has changed at relevant
layers):

1. when I dock the laptop via DP1, the port gets connected (laptop screen
flickers once, as normal) but the external monitor does not take itself out of
sleep mode. I have to go to Display settings panel, move monitor arrangement by
1px or whatever so Apply button becomes active, click Apply - boom monitor
wakes up.

  This is not an issue when connecting via HDMI - monitor lights up
immediately. So must be something with DP MST negotation?

2. when disconnecting laptop from HDMI, the port doesn't recognize the monitor
has been disconnected anymore. Display settings panel shows the external
display is still active, laptop lid close doesn't suspend, etc. This is a
regression, because HDMI always worked fine for several previous kernel
releases (being my "avoid docking problems today" workaround).

3. Flickering we're already discussing here.

Still, as of 4.9, all the things have gotten a ton better.

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