prepare_to_wait(&itv->dma_waitq, &wait, TASK_INTERRUPTIBLE);
/* if no UDMA is pending and no UDMA is in progress, then the DMA
is finished */
prepare_to_wait(&itv->dma_waitq, &wait, TASK_INTERRUPTIBLE);
/* if no UDMA is pending and no UDMA is in progress, then the DMA
is finished */