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Original question:

Linux/TUSB8041: USB compliance test fail

TUSB8041: USB compliance test fail in Rx (Can't enter Loopback mode)

Mentor Tseng
Prodigy 195 points
Part Number: TUSB8041

Dear Sir,

   In my application the TUSB8041 is used to expand 4 port usb from X86 system. The upstream is connected to PCH of X86 system and 4 downstream port is as USB connector. But in USB compliance test of out SI lab, the RX signal couldn't be test because it couldn't get in loopback mode. The below information is get when RX compliant test running. Please help us to solve this issue and let the compliant test of Rx keep to go. Thanks. 

Note:  The TUS8041 EVM has been run USB compliant test in our lab. But it still couldn't get in loopback mode in Rx test.

  • 0
    TI__Guru 60870 points
    Hi Mentor,

    Can you confirm that the host controller driver is not resetting the TUSB8041 ports went they attempt to enter loopback? We have found many host controllers will reset the downstream ports of the hub when they report a port status of loopback. Otherwise, can we get a photo of the test setup. we don't have issues in our lab.

    Regards,
    JMMN
  • 0 in reply to JMMN
    Prodigy 195 points
    Hi JMMN,

    The test equipment of my lab is Keysight N5990A and follow the document (Keysight N5990A Test Automation Software Platform for USB)to do compliant Test. Could you give me your setting of equipment? I don't know what setting of equipment is you want to see. Thanks.

    - The setting of your measurement equipment.
    - Could you give the RX report of TUSB8041?

    Thanks.
  • 0 in reply to Mentor Tseng
    TI__Guru 60870 points

    The toolset we use in the TI labs is the Teledyne LeCroy PERT setup:

     

    http://cdn.teledynelecroy.com/files/pdf/usb3.1-test-suite-datasheet.pdf

     

    We’ve also had customers use the Keysight setup without issues. 

     

    To keep the hub downstream ports in loopback mode, they need to confirm that the XHCI controller is not resetting the ports or the hub.  For typical lab testing, we install the XHSETT tool from usb.org on the host controller to prevent any unexpected XHCI driver interactions.

     

    We’ve had 100s of customer run compliance on this device without any issues.  If they can confirm that the driver is not resetting the ports, they can try adjusting (increasing) the LFPS amplitude to see if that impacts the RX lock.

     

    If they can provide information on the failure from the Keysight tools that would be helpful as well.

  • 0 in reply to JMMN
    TI__Guru 60870 points
    Resolving over direct email to share protected data.
  • 0 in reply to JMMN
    Prodigy 195 points
    Hi JMMN,

    Thanks for your help. The RX compliance test could be done by entering the loop back mode. But the Rx test result is fail, 8 points of SJ frequency are fail. But when we close the CTLE in test equipment, the RX compliance is PASS.

    - Rx compliance test Fail: 8 points of Sj frequency are fail with CTLE on.
    - Rx compliance test PASS: when CTLE is off
    - Tx compliance test is PASS

    I think the CTLE will help the signal quality to become better. But in my case, it seems reversal.
    Colud you help us how to do in next step? Any setting of TUSB8041 could be done? Thanks.
  • 0 in reply to Mentor Tseng
    TI__Guru 60870 points
    That's very strange CTLE should help. Can you send me the test report over direct email or accept my friend request and send it over private E2E?

    Thanks,
    JMMN
  • 0 in reply to JMMN
    Prodigy 195 points
    Hi JMMN,
    I has send the result through private E2E massage. Pass result is CTLE off, and fail result is CTLE on.
  • 0 in reply to Mentor Tseng
    TI__Guru 60870 points
    Hi Mentor,

    Thanks for the files, we will have our Keysight platform from calibration soon so we can look at CTLE internally.

    Reards,
    JMMN