LAN/NIC problem

[MarkHaysHarris777]

Our currently lead on this investigation is toward the power quality that RTL8211 received, namely small voltage ripping wave on the VDD and AVDD line. It seems that certain RTL8211 chip sensitive to this voltage noise. We have testing this theory on the other vendor board and initial results seems works well.

We are collecting more GbE affected Pine A64+ boards and our hardware engineering team are focusing into this path. The focus point is on one inductor (ferrite bead) at one of the VDD power line to RTL8211 chip.

P/S: Appreciate Marcus and Tom kaiser effort on this finding.

Regards,
TL Lim

Is the VDD and AVD issue that TL mentions the same as the VDD33 concern that tkaiser had discussed as a possible factor?

It is apparently a possible factor on some of the test boards , but it is not a facotr on my three boards... the voltage is absolutely clean... no ripples at all;  particularly if the units are running on battery.  But even with the clean PHY_VDD33 voltage one of my three boards does not work in GbE mode (drops packets, drops pings, locks up on scp transfers, and fails iperf3 tests miserably even with longsleep tuning. On my failing board the PHY_VDD33 voltage is NOT an issue.

There is another way to say this... with an inductor on the PHY_VDD33 line, the iperf3 tests will probably improve on the two boards I have that do work in GbE mode ! I have shown this on my boards by running them from very clean power (battery) with filtered inputs to the euler bus; however, putting an inductor on the PHY_VDD33 line on my non working GbE board is not going to make it magically work. Whatever is wrong on that board is NOT power related, at least not on the VDD33 line; something else is wrong with that particular board.