how does usb cppi dma work?

Yes,I use c6748 and I have install its startereware package.I have read the cppi41dma.c file, but I am confused. I want to add cppidma to usb_dev_bulk.

Please help me,thanks.

Hi,
Current DMA implementation is only for USB mass storage device, if interested you can write and enable DMA support on your own for USB dev bulk.

processors.wiki.ti.com/.../StarterWare_USB

When I add CPPIDMA's functionality to usb_dev_bulk,I've had a  problem,In the host,I use usb_bulk_write() to send data,but when it sends a number of data, it will be blocked and no longer send data! My code is as follows:

static void
HandleEndpoints(void *pvInstance, unsigned int ulStatus, unsigned int ulIndex)
{
    const tUSBDBulkDevice *psBulkInst;
    tBulkInstance *psInst;

    ASSERT(pvInstance != 0);

    //
    // Determine if the serial device is in single or composite mode because
    // the meaning of ulIndex is different in both cases.
    //
    psBulkInst = (const tUSBDBulkDevice *)pvInstance;
    psInst = psBulkInst->psPrivateBulkData;


#ifdef DMA_MODE
    unsigned int pendReg=0;

    // Get the Starvation interrupt status
    CppiDmaGetINTD0Status(g_USBInstance[ulIndex].uiUSBInstance);

    // Get the DMA Interrupt status
    pendReg = CppiDmaGetPendStatus(g_USBInstance[ulIndex].uiUSBInstance);

#endif

    //
    // Handler for the bulk OUT data endpoint.
    //
    if(ulStatus & (0x10000 << USB_EP_TO_INDEX(psInst->ucOUTEndpoint)) ||
            (pendReg & CPDMA_RX_PENDING))
    {

#ifdef DMA_MODE
        ProcessDataFromHost_DMAMODE(pvInstance, ulStatus, ulIndex, pendReg);
#else
        ProcessDataFromHost(pvInstance, ulStatus, ulIndex);
#endif

    }

    //
    // Handler for the bulk IN data endpoint.
    //
    if(ulStatus & (1 << USB_EP_TO_INDEX(psInst->ucINEndpoint)) ||
            (pendReg & CPDMA_TX_PENDING))
    {

#ifndef DMA_MODE
        ProcessDataToHost_DMAMODE(pvInstance, ulStatus, ulIndex, pendReg);
#else
        ProcessDataToHost(pvInstance, ulStatus, ulIndex);
#endif
    }
}

static tBoolean
ProcessDataFromHost_DMAMODE(const tUSBDBulkDevice *psDevice, unsigned int ulStatus,
                                                            unsigned int ulIndex,unsigned int pendReg)
{
    unsigned int rxBuffer;
    unsigned int ulEPStatus;
    tBulkInstance *psInst;
    tUSBBuffer *psBuffer;

    // Get a pointer to our instance data.
    psInst = psDevice->psPrivateBulkData;
    psBuffer = (tUSBBuffer *)psDevice->pvRxCBData;

    // Get the endpoint status to see why we were called.
    ulEPStatus = USBEndpointStatus(g_USBInstance[ulIndex].uiBaseAddr, psInst->ucOUTEndpoint);

    //Clear the status bits.
    USBDevEndpointStatusClear(g_USBInstance[ulIndex].uiBaseAddr, psInst->ucOUTEndpoint, ulEPStatus);

    enableCoreRxDMA(g_USBInstance[ulIndex].uiUSBInstance, psInst->ucOUTEndpoint);

    //During receive operation, we need to wait in loop till we recive all data
    while(CppiDmaGetPendStatus(g_USBInstance[ulIndex].uiUSBInstance) & CPDMA_RX_PENDING)
    {
        rxBuffer = dmaRxCompletion(g_USBInstance[ulIndex].uiUSBInstance, psInst->ucOUTEndpoint);

        psBuffer->pfnCallback(psBuffer->pvCBData,USB_EVENT_RX_AVAILABLE,512,rxBuffer);

#if 0
        times++;
        UARTPuts("times:", -1);
        UARTPutHexNum(times);
        UARTPuts("\r\n", -1);

        *((char *)rxBuffer+20) = 0;

        UARTPuts("rxBuffer:", -1);
        UARTPuts((char *)rxBuffer+8, -1);
        UARTPuts("\r\n", -1);
#endif

        //
        //Load another BD to the receive queue
        //
        doDmaRxTransfer(g_USBInstance[ulIndex].uiUSBInstance, MAX_TRANSFER_SIZE,
            (unsigned char *)rxBuffer, psInst->ucOUTEndpoint);
    }

    USBDevEndpointDataAck(psInst->ulUSBBase, psInst->ucOUTEndpoint,true);

    return (true);
}

Can anyone help me? thanks.