RING_SYNC_2
I915_READ(RING_SYNC_2(engine->mmio_base));
#define GEN6_RVESYNC (RING_SYNC_2(RENDER_RING_BASE))
#define GEN6_VVESYNC (RING_SYNC_2(GEN6_BSD_RING_BASE))
#define GEN6_BVESYNC (RING_SYNC_2(BLT_RING_BASE))
#define GEN6_VEVSYNC (RING_SYNC_2(VEBOX_RING_BASE))
I915_READ(RING_SYNC_2(engine->mmio_base)));
I915_WRITE(RING_SYNC_2(engine->mmio_base), 0);