# ./test
Select a serial port (3/4): 3
tx_buffer:
hello world!
[ 137.284539] of_dma_request_slave_channel: dma-names property of node '/serial@ff4d0000' missing or empty
[ 137.284583] dw-apb-uart ff4d0000.serial: failed to request DMA, use interrupt mode

我整个例程都是官方直接复制进行了交叉编译，用UART4也是这种情况，应该如何解决？