IWR6843AOP: Uart with DMA on mss can only send out data, but can not receive

My code could work with no dma mode, but lost one byte some time. So I want to use dma mode to avoid the lost of data.

The new code refer to the example "C:\ti\mmwave_sdk_03_06_00_00-LTS\packages\ti\drivers\uart\test\xwr68xx".

The init code:

    // let uart b work with tx/rx
    extern UART_Config UART_config[];
    UartSci_HwCfg* hwcfg = (UartSci_HwCfg*) UART_config[1].hwAttrs;
    hwcfg->duplexity = UartSci_Duplexity_FULL;
    
#if UART_WIFI_USE_DMA
    DMA_init ();
#endif
    UART_init();
    
    UART_Params_init(&uartParams);
    uartParams.writeDataMode = UART_DATA_BINARY;
    uartParams.readDataMode = UART_DATA_BINARY;
    uartParams.readReturnMode = UART_RETURN_FULL;
    uartParams.readEcho = UART_ECHO_OFF;
    uartParams.clockFrequency = gFdMCB.cfg.platformCfg.sysClockFrequency;
    uartParams.baudRate       = gFdMCB.cfg.platformCfg.commandBaudRate;
    uartParams.isPinMuxDone   = 1U;
    uartParams.readTimeout = 50;

#if UART_WIFI_USE_DMA
    DMA_Params      dmaParams;
    DMA_Params_init(&dmaParams);
    DMA_Handle   DMAHandle;
    DMAHandle = DMA_open(1, &dmaParams, &errCode);
    if (DMAHandle == NULL)
    {
        printf ("Error: Unable to open the DMA Instance [Error code %d]\n", errCode);
        log_write_fmt ("Error: Unable to open the DMA Instance [Error code %d]\n", errCode);
        return;
    }

    uartParams.dmaHandle = DMAHandle;
    uartParams.txDMAChannel = 1;
    uartParams.rxDMAChannel = 2;

#endif

    /* Open the wifi UART Instance: */
    UART_Handle uartHandle = UART_open(1, &uartParams);
    if (uartHandle == NULL)
    {
        //System_printf("Error: Unable to open the Wifi UART Instance\n");
        log_write("Error: Unable to open the Wifi UART Instance\n");
        tvt_debugAssert (0);
        return;
    }

I use UART_write and UART_read to tx/rx, and Uart A to write log. So I could see that UART_read always return 0, while my PC could receive data from the 6843.

When disable dma by   

#define UART_WIFI_USE_DMA 0

the code would work fine.