[Bug 108825] Regression Raven Ridge: Banding on eDP display

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=108825

--- Comment #6 from Nicholas Kazlauskas <nicholas.kazlauskas at amd.com> ---
(In reply to Samantha McVey from comment #5)
> I have bisected it to commit: drm/amd/display: Support amdgpu "max bpc"
> connector property
> 307638884f721b02b6a54ee8b351c5b4434bd4a6 Author: Nicholas Kazlauskas
> <nicholas.kazlauskas at amd.com>

This isn't a regression from 4.19 but rather a fix for 4.18 where bpc was
uncapped from 8 unconditionally. It locked out high refresh modes for high
resolution panels with max bpc greater than 8.

The reported 6bpc in your dmesg log comes from DRM itself and not amdgpu. It's
what's being reported as being supported by your panel from its EDID. I'm not
sure if this is the panel itself reporting itself wrong or if there's a quirk
affecting it from the edid qurik list in drm_edid.c.

You can try reverting my patch on amd-staging-drm-next to see if you still get
the banding.

Or you could try setting the "max bpc" property to something higher (like 16).
You should be able to add this as an "Option" to a conf file in
/etc/X11/xorg.conf.d for your Monitor.

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