AM3358: BBB reboot issue with Ethernet PHY

Hi Hans,

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

Hi Biser,

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

Cheers

Hans

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).

Biser Gatchev-XID said:

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?

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.

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.

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.