[Bug 93826] 2560x1440 @144Hz graphic glitches and bad refresh rate

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=93826

--- Comment #68 from iuno at posteo.net ---
(In reply to Alex Deucher from comment #67)
> Do you get flickering at 144Hz without forcing the mclk to high?  I.e.,
> without these patches:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/
> ?id=0a646f331db0eb9efc8d3a95a44872036d441d58
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/
> ?id=58d7e3e427db1bd68f33025519a9468140280a75
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/
> ?id=09be4a5219610a6fae3215d4f51f948d6f5d2609
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/
> ?id=2275a3a2fe9914ba6d76c8ea490da3c08342bd19

Yes, I've experienced that before and just tested it again.

> > Do you know how this works on Windows? Do they increase voltage without
> > raising clocks and could this be an option for amdgpu too?
> 
> It's not the mclk frequency or voltage, it's the blanking period for the
> display timing, it's apparently too short on some monitors at very high
> refresh rates for the mclk to finish switching in time.  If part of the mclk
> switch happens outside of the vblank period, you end up with flickering or
> other display artifacts.

I assumed it is related to any voltage because higher sclk helps too. I'll just
call sclk/mclk dpm states "sdpm" and "mdpm"

auto (sdpm 0, mdpm 0 or switching through states): very bad flickering and
artifacts
sdpm 1-7, mdpm 0: better (still flickering/artifacts, but only when bigger
areas on the screen are updated)
sdpm any, mdpm 1: no flickering and artifacts

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