HW_APB_CTRL0_CLKGATE
DMA_WR(sc, HW_APB_CTRL0_CLR, HW_APB_CTRL0_CLKGATE);
while (!(DMA_RD(sc, HW_APB_CTRL0) & HW_APB_CTRL0_CLKGATE))
DMA_WR(sc, HW_APB_CTRL0_CLR, HW_APB_CTRL0_CLKGATE);
while (DMA_RD(sc, HW_APB_CTRL0) & HW_APB_CTRL0_CLKGATE)