Jochen Schroeder, please respond to all of the following: 1) To capture relevant debugging logs, could you please undo the WORKAROUND, boot into a Ubuntu kernel (not upstream) and execute the following in a terminal: apport-collect 1767701
2) The next step is to fully reverse commit bisect from kernel 4.15 to 4.16.5 in order to identify the last bad commit, followed immediately by the first good one. Once this good commit has been identified, it may be reviewed for backporting. Could you please do this following https://wiki.ubuntu.com/Kernel/KernelBisection ? Please note, finding adjacent kernel versions, or providing a commit from a kernel version bisect is not fully commit bisecting. Also, the kernel release names are irrelevant for the purposes of bisecting. It is most helpful that after the fix commit (not kernel version) has been identified, you then mark this report Status Confirmed. Thank you for your help. ** Tags added: bionic kernel-fixed-upstream kernel-fixed-upstream-4.16.5 needs-reverse-bisect regression-release ** Description changed: 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. + 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. + + WORKAROUND: Pass kernel boot parameter: + amdgpu.dc=0 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1767701 Title: amdgpu WQHD resolution not working To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1767701/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
