如果是三个不同的SPI接口，则不会影响。

When using DMA for SPI transmit, the DMA_DONE interrupt signifies that the DMA FIFO is empty. However, at this point there may still be data in the SPI DMA FIFO waiting to be transmitted. Therefore, software needs to poll TXS in the SPI_STAT register until it goes low for 2 successive reads, at which point the SPI DMA FIFO will be empty. When the SPIF bit subsequently goes high, the last word has been transferred.

那个SPI DMA FIFO对应的是哪个寄存器，有什么办法可以使其为空吗？

通常DMA传输完成后，将接口的使能关闭，将DMA的使能关闭即可。再次传输时，可以再次为其使能。

*pDMA6_START_ADDR = (unsigned long)start_addr;

那么传输过来的数据就直接放在了，，，以start_addr为起始地址的一段存储空间中了，，