Using mainline kernel team ppa for Trusty http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.13-rc1-trusty/ I could reproduce the problem for Mobility Radeon HD 5650/5750 / 6530M/6550M
I didn't test the patch of kkolasa, but could help supply a .deb for testing, or build in the kernel mainline the patch for testing.
Using mainline kernel team ppa for Trusty http:// kernel. ubuntu. com/~kernel- ppa/mainline/ v3.13-rc1- trusty/ I could reproduce the problem for Mobility Radeon HD 5650/5750 / 6530M/6550M
I didn't test the patch of kkolasa, but could help supply a .deb for testing, or build in the kernel mainline the patch for testing.