https://bugzilla.kernel.org/show_bug.cgi?id=89731
--- Comment #5 from Lorenzo S. lorenzo.stanco@gmail.com --- Just for the record, I'm on Acer 4820TG with ATI Mobility Radeon HD5470 and I'm experiencing the same exact issue described in https://bugs.freedesktop.org/show_bug.cgi?id=88927
I've not tried suggested patch because I'm not practical about kernel recompiling, and I'm on Xubuntu 15.04 with kernel 3.19.0-15-generic. Anyway I reported some logs and infos on my comment there, hope it can helps: https://bugs.freedesktop.org/show_bug.cgi?id=88927#c4