Radeon HD5770 incorrect refresh rate via display port
Original bug report was filed here https://bugzilla.kernel.org/show_bug.cgi?id=214369 but no response and it seems here is a more right place. I just test it with win7 and old catalyst version (10-12) - the card sets video mode correctly. But my previous test with win7 and some other driver version (can't remember it was a while ago) was showing the same issue.