Created attachment 145545 [details]
After setting the gamma or color temperature through various methods (redshift -m randr, redshift -m drm, GNOME night shift on xorg or wayland) horizontal artifacts begin to flicker. This does not severely obscure the screen but appears as small lines horizontal lines flickering quickly. This notably does not happen using the "vidmode" method of redshift (https://github.com/jonls/redshift/blob/master/src/gamma-vidmode.c). I've tested this on multiple displays.
The effect is more noticeable on darker backgrounds.
Steps to reproduce:
1) Use GK104/NVE0 on Xorg or Wayland.
2) Try to adjust color temperature or gamma with software such as redshift (-m randr or drm).
I've attached the dmesg log, note that I am not certain the gnome-shell segfaults have anything to do with this issue.
Linux desktop 5.2.0-2-amd64 #1 SMP Debian 5.2.9-2 (2019-08-21) x86_64 GNU/Linux
NVIDIA Corporation GK104 [GeForce GTX 770]
Also note that this flickering is not similar to the flickering that occurs when using nouveau without a compositor or vsync, and occurs on a static screen.
We've recently started to implement more advanced color management handling, however I think that's only bound for v5.4. I'm not sure if anything was really fixed in those, but it may be worth testing on latest if possible (e.g. drm-next).
Can you also play with dithering mode? e.g. set it to "static 2x2"?
(In reply to Ilia Mirkin from comment #2)
> We've recently started to implement more advanced color management handling,
> however I think that's only bound for v5.4. I'm not sure if anything was
> really fixed in those, but it may be worth testing on latest if possible
> (e.g. drm-next).
> Can you also play with dithering mode? e.g. set it to "static 2x2"?
Setting dithering to 'static 2x2' fixes the issue. I will try testing the 5.4rc soon and see if that solves the issue as well.
Wait, why is dithering even a thing here -- are you using 10bpc formats? Or do you have a LVDS/eDP panel that can only do 6bpc?