[Bug 110659] pageflipping seems to cause jittering on mouse input when running Hitman 2 in Wine/DXVK with amdgpu.dc=1

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=110659

--- Comment #19 from Nicholas Kazlauskas <nicholas.kazlauskas at amd.com> ---
(In reply to tempel.julian from comment #18)
> Huh, with modesetting driver, those patches eliminate the stutter when new
> windows are shown. Does the xf86-video-amdgpu driver need adjustments for
> this?

It should eliminate stuttering for that case in xf86-video-amdgpu if it's the
problem I think it is (double buffering the cursor).

> 
> However, turning on nightlight in Plasma Wayland still causes stutter, which
> is not there with amdgpu.dc=0.

1. Gamma updates are slow updates that do a lot of register programming.
Nightlight and RedShift issue a lot of these updates.

2. Gamma updates, like everything that isn't a cursor update, currently target
the next vblank period.

3. If the pageflip is in a separate commit or update than the gamma update,
then it'll need to wait for the gamma update to finish and for the next vblank
interval. If this takes too long then we might miss the next vblank interval
and have to wait for the one after that.

I think it's a combination of these 3 issues. Even though it's Wayland and
should be using the full atomic API, I'm not sure if plasma is actually issuing
all that state in the same commit or not.

My guess would be no, since you're seeing the stuttering. We do have a bug with
(2) for legacy gamma updates, since there isn't really any reason those should
be waiting for the next flip / vblank other than to be consistent with the rest
of the atomic commit framework.

> RedShift btw. is completely broken with amdgpu.dc=1 + modesetting DDX, it
> simply has no effect anymore (not related to the experimental atomic
> modesetting patches).

Not sure what the issue here would be. Gamma seems to work fine for legacy and
atomic on amdgpu (we pass the IGT tests for this) and it works fine in legacy
desktops like GNOME on Xorg with the xf86-video-amdgpu DDX.

Was this still on Plasma, but on X?

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