PRIME output slaving allows one GPU to produce buffers that will be displayed by another GPU.
A key element that has been missing, however, is synchronization. Without a way to synchronize composition on the rendering GPU with scanout on the displaying GPU, there is no good way to avoid tearing artifacts on PRIME setups. Synchronizing between PRIME master and slave required changes throughout the stack to enable the necessary communication between drivers.
Over the past year, NVIDIA has upstreamed patches to the X server, the modesetting driver, and the i915 DRM driver, and implemented the requisite changes in the NVIDIA driver to enable PRIME Synchronization. In this talk, we will present the challenges faced in implementing PRIME Synchronization support, outline what other drivers need to do in order to support PRIME Synchronization, and discuss steps to be taken moving forward.