RING_SYNC_1
ee->semaphore_mboxes[1] = I915_READ(RING_SYNC_1(engine->mmio_base));
#define GEN6_RBSYNC (RING_SYNC_1(RENDER_RING_BASE))
#define GEN6_VRSYNC (RING_SYNC_1(GEN6_BSD_RING_BASE))
#define GEN6_BVSYNC (RING_SYNC_1(BLT_RING_BASE))
#define GEN6_VERSYNC (RING_SYNC_1(VEBOX_RING_BASE))
I915_READ(RING_SYNC_1(engine->mmio_base)));
I915_WRITE(RING_SYNC_1(engine->mmio_base), 0);