DMACTL_STOP
CSR_WRITE(sc, DMACTL_H2M, DMACTL_STOP);
CSR_WRITE(sc, DMACTL_M2H, DMACTL_STOP);
WAIT_FOR_CLR(sc, DMACTL_H2M, DMACTL_STOP);
WAIT_FOR_CLR(sc, DMACTL_M2H, DMACTL_STOP);