RING_BBADDR
ee->bbaddr = I915_READ(RING_BBADDR(engine->mmio_base));
bbaddr = I915_READ64_2x32(RING_BBADDR(engine->mmio_base),
bbaddr = I915_READ(RING_BBADDR(engine->mmio_base));
CTX_REG(regs, CTX_BB_HEAD_L, RING_BBADDR(base), 0);