RING_SYNC_0
ee->semaphore_mboxes[0] = I915_READ(RING_SYNC_0(engine->mmio_base));
#define GEN6_RVSYNC (RING_SYNC_0(RENDER_RING_BASE))
#define GEN6_VBSYNC (RING_SYNC_0(GEN6_BSD_RING_BASE))
#define GEN6_BRSYNC (RING_SYNC_0(BLT_RING_BASE))
#define GEN6_VEBSYNC (RING_SYNC_0(VEBOX_RING_BASE))
I915_READ(RING_SYNC_0(engine->mmio_base)));
I915_WRITE(RING_SYNC_0(engine->mmio_base), 0);