https://bugzilla.kernel.org/show_bug.cgi?id=47351
--- Comment #6 from Alex Deucher alexdeucher@gmail.com 2013-04-29 14:20:38 --- (In reply to comment #5)
I have the same behaviour on my HP 4545s laptop if I try to use discrete video card (HD7500/7600). I managed to get it work (more or less) on integrated 7240G, but I get blank screen having tried to switch to discrete video. Can I provide any additional information to help to resolve the issue?
Most hybrid laptops are mux-less meaning there are no displays physically connected to the discrete GPU. For display you have to use the integrated GPU. The discrete GPU can only be used for offscreen rendering. Do display that rendering, it has to be copied to the integrated GPU. There is limited support for this in newer xservers (1.13.x and newer).