https://bugzilla.kernel.org/show_bug.cgi?id=36812
--- Comment #2 from James Cloos cloos@jhcloos.com 2011-06-07 00:47:29 --- Longer than that.
The box is usually headless; when I first got it the missing firmware prevented booting, so I added radeon.modeset=0 to the grub config and manually changed that for those occasions when I moved the box to the TV. Today I changed the grub config in honour of the upcoming 3.0. ☺
(That it boots now even though it fails to load that firmware is a nice progression.)
My best guess, based on the timestamps of my .config archive, is that I last connected it to the TV during the 38-rc1 timeframe.