https://bugs.freedesktop.org/show_bug.cgi?id=99857
--- Comment #7 from Andrey Grodzovsky andrey.grodzovsky@amd.com --- Well, your dmesg shows 4.9 kernel which is really old, so I would give a try. If you still have it on 4.18 a new log can be more useful to look at. I think you can always just manually install *.deb packages on your system without any distro upgrades.
Just try directly installing packages from here using sudo dpkg -i *.deb http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.18/