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DP83867ERGZ-S-EVM: Connecting two DP83867ERGZ-S-EVM boards together

hermann picot
Prodigy 30 points

Part Number: DP83867ERGZ-S-EVM

Hi,

I would like to report an issue observed with the following setup:

  • First laptop connected to a first DP83867ERGZ-S-EVM board via RJ45
  • First DP83867ERGZ-S-EVM board connected to a second DP83867ERGZ-S-EVM board via SGMII (SO_P/N to SI_P/N using 25 cm SMA cables)
  • Second laptop connected to the second DP83867ERGZ-S-EVM board via RJ45

When running a 1 Gbps Ethernet TCP test using iperf3 in client/server mode, we observe some retries. The frequency of these retries is variable: they may appear after about 12 minutes, after one or several hours, or, in the best case, only after around 16 hours.

If we connect the two laptops directly with a RJ45 cable, without using the DP83867ERGZ-S-EVM boards, no retries are observed (tested over 60 hours).

I have two questions:

  1. Have you already tested such a configuration?
  2. Do you have any idea about the root cause of this issue and a possible solution or workaround?

Best regards,
Hermann

  • 0
    TI__Mastermind 37195 points

    Hi Hermann,

    To answer your questions:

    1. We have tested this EVM in a back-to-back configuration like you describe. I am not aware of any issue with this configuration, so will need to see if we've tested this over such a time period.

    2. I have a couple of questions to get a better idea:

    • Does the SMA cable length affect these retries? 25cm seems to exceed our typical xMII length of 6" so I'm curious if this could be impacting the performance.
    • Do you notice any values in register 0x0015 on either PHY when the retry condition happens? This would suggest an error is received from the RJ-45 connection on the relevant PHY.

    Best,

    Shane

  • 0 in reply to Shane Hauser
    Prodigy 30 points

    Hi Shane,

    I discover that the Ethernet "pause frame" was not enabled on the failing case. If I disable it on my working configuration Laptop - Ethernet cable - Laptop, I get also some retries after 1 hour or more.

    Do you know if "pause frame" is supported and can be activated on the DP83867ERGZ-S-EVM board?

    B.R.
    Hermann

  • 0 in reply to hermann picot
    TI__Mastermind 37195 points

    Hi Hermann,

    Does setting 0x0004[10] on both EVMs fix the issue? This bit should allow DP83867 to advertise support for pause frames:

    By default this is disabled because pause frames need to be supported by the connected MAC before we can advertise support. If both of your laptops support this capability then it would be ok to enable this on both PHYs.

    Best,

    Shane