ATAC_CH0D0_DMA
rdmsr(ATAC_CH0D0_DMA + 2 * adev->devno, reg, dummy);
wrmsr(ATAC_CH0D0_DMA + 2 * adev->devno, reg | 0x80000000UL, 0);
rdmsr(ATAC_CH0D0_DMA + 2 * adev->devno, reg, dummy);
wrmsr(ATAC_CH0D0_DMA + 2 * adev->devno, reg, 0);