https://bugzilla.kernel.org/show_bug.cgi?id=60523
--- Comment #40 from queryv+fd@gmail.com --- (In reply to Alex Deucher from comment #39)
Created attachment 107254 [details] fix for 3.11
The attached patch seems to fix it for me.
That doesn't seem to fix it for me (6870). I first tried 3.11-rc6 + drm-next-3.12-wip (ee31b2b), and then 3.11-rc6 + the standalone patch you attached.
In the former case, when trying to force a performance level I still got: echo: write error: Invalid argument
And the power level still idles at: power level 2 sclk: 90000 mclk: 105000 vddc: 1175 vddci: 1150
gcc --version gcc (GCC) 4.8.1 20130725 (prerelease)