[Bug 201795] [Regression] Wrong 4k resolution detected with DisplayPort to HDMI adapter on amdgpu

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=201795

--- Comment #16 from Nicholas Kazlauskas (nicholas.kazlauskas at amd.com) ---
By default, amdgpu DC doesn't perform any sort of display scaling. It relies on
the monitor/TV's scaler itself to do the work, which might be producing the
black bars.

When you do set the scaling mode via the connector property "scaling mode", the
driver will perform the scaling itself. However, this scaling is done on
whatever the preferred mode for the monitor is.

I believe that the preferred mode for your TV is 4096x2160:

"4096x2160" 30 297000 4096 4184 4272 4400 2160 2168 2178 2250 0x40 0x5

This should be the timing used when display scaling is done by the driver
itself. You might get mirroring to work if you set the connector scaling mode
property, eg:

xrandr --output DisplayPort-0 --set "scaling mode" "Full"

and then try changing the mode on the display or mirroring.

This setting can persist in your xorg.conf as well, I believe it looks
something like:

Section "Monitor"
    Identifier "DisplayPort-0"
    Option "scaling mode" "Full"
EndSection

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