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AM5716: PRU Ethernet issue

Part Number: AM5716

Hi experts

I would like to ask a question about AM5716 PHY configuration. We did an experiment. The two ethernet ports on the board could communicate normally, but after exchanging the two PHYs on the board, Ping would fail. We only modified the PHY ID on the DTS. We have verified the phy loopback. The verification results show that the phy side loopback is normal. The attachment is the device tree. Can you help me see where the configuration problem is?

0361.am57xx-idk-common.dtsi

  • Hi,

    Can you clarify what are you doing with the phys:

    1. Replacing the existing phy with identical another phy
    2. Swapping the two phy's used.

    As per my understanding, the phy which are swapped here are identical phy. I am also assuming that this is being carried out on IDK board.

    Can you also please tell me why are you doing this?

    We only modified the PHY ID on the DTS

    You should not update the phy ID. Th phy ID are set by bootstrapping the phy using the schematic design. Hence, as long as the schematic isn't changed, the ID should also not be changed. Same goes for the reset gpio used by the phy.

    Regards,
    Tanmay

  • Hi Tanmay

    Sorry for the confusion, it refers to swap the two phy's used., both of which are DP83822. This operation is performed on a customized board.

    Since it is the same PHY P/N, cannot we directly modify the PHY ID after swap? What other modifications should we make?

    Best Regards

    Ethan

  • Hi Ethan,

    What I am trying to say here is that since both are identical phy, no modifications are needed.

    Regards,
    Tanmay

  • Hi Tanmay

    I don't quite understand. If so, there should be no problem with the modification. Why can I see the link status when unplugging and plugging the Ethernet cable, but the ping fails?

  • Hi Ethan,

    Why can I see the link status when unplugging and plugging the Ethernet cable, but the ping fails?

    Not sure why this is happening, but no changes are required in the software for an identical phy replacement. It is similar to just replacing a chip with a new one, you needn't do any software changes for this.

    Can you confirm that the ping was working before the swap? Maybe there was some other error introduced while swapping. Can you try a phy-loopback test?

    Also why was the swap done? Is it a one time thing? 

    Regards,
    Tanmay 

  • Hi Tanmay

    1. We modified the strap mode of phy to match with the phy ID modify
    2. We have done the PHY loopback test and it is no problem. 
    3. If we don’t swap the PHY ID, it can work normally, but if we modify the PHY ID, it will not work properly. How to modify the PHY ID? Is the PHY ID of CPSW0 need smaller than the PHY ID of CPSW1 (currently the PHY ID of CPSW0=2 and the PHY ID of CPSW1=11)?

    Since the customer's two PHYs are on the base board and core board respectively, it is currently found that the PHY on the base board cannot pass the stress test. We are investigating the problem.

  • Hi,

    We modified the strap mode of phy to match with the phy ID modify

    Does this mean there are some hardware changes? or do you change the strap register post PHY reset?

    Regards,
    Tanmay