[FS#687] Meraki MR24: Ethernet interface not detected correctly if cable not plugged at boot time

[LEDE Bugs]

The following task has a new comment added:

FS#687 - Meraki MR24: Ethernet interface not detected correctly if cable not plugged at boot time
User who did this - Christian Lamparter (chunkeey)

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Chris Blake was also able to reproduce this issue with his unit. Problem is we are currently stuck on what's going on with regards to the AR8035.

It's likely that the u-boot is powering down the (inactive) phy before handing
control over to the LEDE installation. This is because the MX60 (same Generation, but it is the router) does disable the ports as some sort of "security measure".

I think in order to debug this, it will be necessary to look what is happening to the phy chip. Can you probe the individual pins of the chip with a digital oscilloscope? The most important pins would be the reset pin (Pin 1), the XI clocks (Pin 5 and Pin 4). Of course it would be better, if you can also probe the MDC/MDIO(pin 40 and pin 39) and see if u-boot is disabling the PHY and how.

you can find a datasheet with the pinout with google
(i.e.:  )

The Pinout is on page 4. The Power-on Sequence is explained on page 26.

Note: We looked into meraki-linux's source as well. But there are no modifications to the emac driver, apart from adding the PHY to the list of known phys. I don't have a MR24 myself, but given this information, I wonder what Meraki's stock firmware is doing in this case. Can you reflash the original firmware and provide a bootlog? Just in case there's some note or hint in it. 
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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=687#comment2380