Kindly refer to the descriptor chaining in Application Note AN220191:
--AN220191 How to Use Direct Memory Access (DMA) Controller in Traveo II Family
In addition, we have DMA sample code in our SDL and you can refer to it.
but i have read this document before i ask this question,i can't find how to use uart dma loop mode and i cant find how to get the progress of the dma transfer
你好，我没太理解你的应用为什么需要时时获取DAM传输的进度或者需要一个什么样的环形DMA。我们SDL （sample driver library）里面有提供UART FIFO + DMA的例程，请先参考例程看是否满足你的需求。如果你没有SDL，请联系我们的分销商或者销售人员。
i have read UART FIFO + DMA example, but i can not know when the fifo is full, so i don not know when to restart the dma