MIX_SRC
regw(sc, DP_MIX, (MIX_SRC << 16) | MIX_DST);
regw(sc, DP_MIX, ((MIX_SRC & 0xffff) << 16) | MIX_SRC);
mach64_bitblt(sc, xs, y, xd, y, width, height, MIX_SRC);
mach64_bitblt(sc, x, ys, x, yd, width, height, MIX_SRC);
regw(sc, DP_MIX, ((MIX_SRC & 0xffff) << 16) | MIX_SRC);
regw(sc, DP_MIX, MIX_SRC << 16);
sc->sc_gc.gc_rop = MIX_SRC;