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AM3358: BBB reboot issue with Ethernet PHY

Genius 5540 points

Hi,

within my (bare metal) application it happens from time to time the Ethernet PHY can't be initialised. This can be fixed by toggling the power, on next boot everything works fine. This happens rarely so that I haven't been able to track down this problem until now.

So I tried to workaround this by a reboot via watchdog - but this leads to an endles loop, the PHY comes back in same unusable state as before.

So it seems rebooting via watchdog is "not cold enough" to solve this issue.

So my question: are there any other possibilities to have a more hard/cold restart of AM3358 CPU?

Thanks!

  • Hi Hans,

    Can you give information what is the PHY part number and what is your hardware connection of the PHY reset signal?

     

    Best Regards
    Biser
  • Genius 5540 points

    In reply to Biser Gatchev-XID:

    Hi Biser,

    it is a BeagleBone Black which comes with an LAN8710A, reset is connected to NRESET_INOUT of AM3358

    Cheers

    Hans

  • In reply to qxc:

    This is a known issue. The problem is that the AM335X nRESET_INOUT (or warm reset) is released at approximately the moment that the PHY latches internally it's bootstrap resistors. Once in a while this happens too soon and the PHY doesn't come out of reset correctly. This can be avoided if the PHY reset is tied to a processor GPIO (it's important that the GPIO stays in low state during reset and at reset release time).

     

    Best Regards
    Biser
  • Genius 5540 points

    In reply to Biser Gatchev-XID:

    Biser Gatchev-XID
    This can be avoided if the PHY reset is tied to a processor GPIO (it's important that the GPIO stays in low state during reset and at reset release time).

    That's no option for me since the layout and connections of BeagleBone Black are fixed and I do not have any influence to them. So...are there any software workarounds? Something that is similar to a manual power cycle?

  • In reply to qxc:

    You can consider using the PMIC_POWER_EN signal to turn off the PMIC. See Table 20-62 in the AM335X TRM Rev. J for details.

     

    Best Regards
    Biser
  • Genius 5540 points

    In reply to Biser Gatchev-XID:

    OK, but how is it turned back on without the need to let the user cycle the power? It should re-power automatically, elsewhere it would be the same like cold reboot done by user.

  • In reply to qxc:

    There is no solution for this on the BB Black you are using.

     

    Best Regards
    Biser
  • Part Number: BEAGLEBK

    I've come up with a software only workaround that can make sure a BBB will always come up with a working Ethernet port - although it can take a few minutes and require several automatic internal power cycles. 

    You can read about it here...

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