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Issues with USB 3G modem on OTG port

Zhiqiang Yuan
Prodigy 40 points

Hi,all:

      We're now testing for Huawei EC1261 usb 3g modem on TI EVM2 board. The BSP is from BSquare. Release version 6.12.03. The usb 3g modem driver is from usbser component(a little custom modification).

      The modem driver has been tested on usb host port, and it has wonderful performance. While on OTG port, the response from modem won't be passed on through the otg driver. The received data is buffered until the committed buffer is filled. But there's little response data. So it hangs on and waits for more data coming in. This makes the dialing fail.

      So I modified the ctd.cpp and make it wait only when handling with endpoint 0. This modification takes effect. The dialing successes. But when opening web page, if configured as DMA0, the speed is very low and cann't be endured. If configured as DMA1, the web page cann't be opened at all. I traced and it seems that nothing received for web request.

      I'm confused that why DMA0 so slow and DMA1 not work at all.(DMA0 used for single packet transferring and may lead to low performance. But the speed seems to be beyond that)

      Does anybody has any suggestion or experience to share?

  • 0
    TI__Expert 7435 points

    Zhigiang,

    While this response will not address your query but it might help you to understand what to expect.

    Can you try your use case scenario on the Linux OMAP solution?  If it works this would provide an indicative performance that can be expected on the OTG port.

    Pl. also refer to the errta that should be available on the OMAP35xx part for any obvious issues w.r.t DMA on the OTG port.

    regards

    swami