Comment 30 for bug 599017

Ok great, the testing done so far appears to be pinpointing this to an issue fixed with newer kernel drm code. It's possible a specific patch resulted in the fix. In that case, the next logical step is to do a git bisection search on the kernel code to locate the fix. The procedure is a little technical but is well documented at https://wiki.ubuntu.com/Kernel/KernelBisection. I'll reassign to the kernel meanwhile.

Btw, drm code can be a bit thorny, and even if the solution is narrowed to a specific git commit, extracting and backporting it might be pretty tricky. But the kernel team can follow up with advice on the issue; please contact them if you have additional questions.