chan2dmadev
td_desc->txd.phys = dma_map_single(chan2dmadev(chan),
err = dma_mapping_error(chan2dmadev(chan), td_desc->txd.phys);
dma_unmap_single(chan2dmadev(td_desc->txd.chan), td_desc->txd.phys,
dma_sync_single_for_device(chan2dmadev(chan), td_desc->txd.phys,