The patches published this morning add support for newer memory controller microcode on newer AMD GPUs and it ends up fixing memory clocking stability for certain GPUs.
The update stems from a bug report about stability and performance issues. In numerous articles I also found very poor performance when using the open-source driver (not Catalyst) for a Sapphire Radeon R7 260X. It turns out these problems come down to DPM issues / microcode problems.
With this latest work, R7 260X re-clocking is re-enabled. Alex Deucher of AMD has marked this set of patches as candidates for merging into existing Linux kernel stable releases.