MMUCR
smc_write_2(sc, MMUCR, MMUCR_CMD_MMU_RESET);
while (bus_read_2(sc->smc_reg, MMUCR) & MMUCR_BUSY)
smc_write_2(sc, MMUCR, MMUCR_CMD_TX_ALLOC | npages);
smc_write_2(sc, MMUCR, MMUCR_CMD_ENQUEUE);
smc_write_2(sc, MMUCR, MMUCR_CMD_RELEASE);
smc_write_2(sc, MMUCR, MMUCR_CMD_RELEASE);
smc_write_2(sc, MMUCR, MMUCR_CMD_RELEASE_PKT);