Alex Goins of NVIDIA's Linux driver team has been working on PRIME synchronization support going back a number of months. Version three of the patches were released last month while today marks V4 being available.
PRIME synchronization should fix tearing for those using a multi-GPU solution like Optimus with an Intel integrated graphics processor and NVIDIA discrete GPU in their laptop or desktop. These patches have been tested with the Intel and Nouveau drivers while NVIDIA also has a yet-to-be-released proprietary driver update for supporting PRIME synchronization.
About the new V4 patches, Goins noted, "The biggest change in this patch set from the last one is the implementation of double buffered PRIME source support in the modesetting driver. Note that this is a basic implementation designed to exercise all of the new ABI functions. It lacks some of the more advanced functionality, such as fenced asynchronous presentation, and OpenGL syncing to the sink's vblank...The most notable change other than source support is disabling reverse PRIME for Glamor-accelerated i915 sinks."