Public bug reported:
After upgrade to bionic the highest detected resolution of my monitor
was 1920x1200 instead of the 2560x1440 that it is capable of and that
worked previously.
My graphics card is a Radeon RX480 and this seems to be related to the
AMDGPU DC changes in kernel 4.15.
Passing amdgpu.dc=0 as boot parameter fixes the issue and the correct
resolution is detected. This is also fixed on latest 4.16.5 upstream
kernel from the kernel ppa, i.e. the maximum resolution is correctly
detected without amdgpu.dc=0 as boot parameter.
attached are the xorg files after booting the 4.15 and 4.16.5 kernels
both without amdgpu.dc=0. The main difference seems to be the probed
modes.
** Affects: linux (Ubuntu)
Importance: Undecided
Status: New
** Attachment added: "xorg log when booting kernel 4.15"
https://bugs.launchpad.net/bugs/1767701/+attachment/5129594/+files/xorg_4.15.log
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https://bugs.launchpad.net/bugs/1767701
Title:
amdgpu WQHD resolution not working
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