[Bug 111506] [amdgpu] VRR/Freesync below the range (LFC) flickering (5700 XT)

[Bug 111506] [amdgpu] VRR/Freesync below the range (LFC) flickering (5700 XT)

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https://bugs.freedesktop.org/show_bug.cgi?id=111506

            Bug ID: 111506
           Summary: [amdgpu] VRR/Freesync below the range (LFC) flickering
                    (5700 XT)
           Product: DRI
           Version: DRI git
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: not set
          Priority: not set
         Component: DRM/AMDgpu
          Assignee: dri-devel@lists.freedesktop.org
          Reporter: asheldon55@gmail.com

I'm getting heavy flickering when dropping below the minimum refresh rate
(default of 40-92, but I also tested 35-92) with Freesync enabled.

It seems to be LFC related as the higher the minimum, the earlier the
flickering kicks in (so it's not a case of the monitor not being able to handle
it at the low end).

I can workaround the problem by changing block of code in freesync.c:

if (in_out_vrr->max_refresh_in_uhz <
            (2 * in_out_vrr->min_refresh_in_uhz))
                in_out_vrr->btr.btr_enabled = false;

with:

if (in_out_vrr->max_refresh_in_uhz <
            (3 * in_out_vrr->min_refresh_in_uhz))
                in_out_vrr->btr.btr_enabled = false;

effectively forcing LFC to only kick in at ~30fps or lower. 

It's possibly a regression as I don't remember the issue occurring with Vega or
Polaris and 5.2 kernel. It's also possible that it's the monitor itself at
fault, and maybe LFC wasn't kicking in properly in older kernels/hardware,
effectively hiding the problem. I will try to get around to testing with Vega
and an older kernel in the future.


System:
MSI 5700 XT
amd-staging-drm-next
Mesa git

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[Bug 111506] [amdgpu] VRR/Freesync below the range (LFC) flickering (5700 XT)

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https://bugs.freedesktop.org/show_bug.cgi?id=111506

--- Comment #1 from Andrew Sheldon <asheldon55@gmail.com> ---
I should note that it doesn't flicker at all with the modification I suggested.
Presumably, LFC is in fact kicking in at 30fps and below, so assuming that's
the case, it's not really LFC in general that is the problem, just LFC when
just below the minimum. 

One possibility is that LFC is somehow generating frames at a rate above the
maximum refresh rate for framerates above 30 and below the minimum (35), since
the range is fairly narrow. Maybe it's tripling rather than doubling the
framerate?

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[Bug 111506] [amdgpu] VRR/Freesync below the range (LFC) flickering (5700 XT)

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https://bugs.freedesktop.org/show_bug.cgi?id=111506

--- Comment #2 from Andrew Sheldon <asheldon55@gmail.com> ---
Looks to be fixed by commit 109b3e3e13507ad0908ff00bc7eb759ed41b88be

drm/amd/display: Improve LFC behaviour

It now smoothly transitions between LFC and VRR without flickering.

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[Bug 111506] [amdgpu] VRR/Freesync below the range (LFC) flickering (5700 XT)

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https://bugs.freedesktop.org/show_bug.cgi?id=111506

Martin Peres <martin.peres@free.fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |MOVED
             Status|NEW                         |RESOLVED

--- Comment #3 from Martin Peres <martin.peres@free.fr> ---
-- GitLab Migration Automatic Message --

This bug has been migrated to freedesktop.org's GitLab instance and has been
closed from further activity.

You can subscribe and participate further through the new bug through this link
to our GitLab instance: https://gitlab.freedesktop.org/drm/amd/issues/897.

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