Freedreno Lands Context Priority Support

Rob Clark of the Freedreno project has landed his context priority patches in Mesa that originate from this past October.

When paired with the changes in Linux 4.15 from the MSM DRM driver, the latest Mesa Git code now offers context priority support for the Freedreno Gallium3D driver. This allows exposing different context priorities for Qualcomm Adreno devices supporting different priority ring buffers.

This priority scheduling isn't currently exposed via any EGL extension or the like at the moment, but if running Linux 4.15 + Mesa 17.4-dev Git and using the FD_MESA_DEBUG=hiprio environment variable, that process should be given higher priority over other graphics work on the system. Currently it just supports modes of high priority and low priority.