ATA_DMA_WR
dmactl &= ~(ATA_DMA_WR | ATA_DMA_START);
dmactl |= ATA_DMA_WR;
dmactl &= ~(ATA_DMA_WR | ATA_DMA_START);
dmactl |= ATA_DMA_WR;
u32 cmd = (rw ? 0 : ATA_DMA_WR) | ATA_DMA_START;
dmactl &= ~ATA_DMA_WR;
dmactl |= ATA_DMA_WR;
dmactl |= ATA_DMA_WR;
dmactl &= ~(ATA_DMA_WR | ATA_DMA_START);
dmactl |= ATA_DMA_WR;