https://bugs.freedesktop.org/show_bug.cgi?id=96326
--- Comment #2 from Jan Ziak 0xe2.0x9a.0x9b@gmail.com --- The flickering disappears after switching from X11 to Linux console (Ctrl+Alt+F1) and back (Ctrl+Alt+F7). mclk transitions 150MHz <-> 1500MHz no longer cause monitor flickering after that.
The code in the Linux kernel executed during the switch to Linux console and back fixes the issue, we just need to pinpoint the code lines responsible for the fix.