[OpenWrt-Devel] Second RGMII ethernet on MT7621?

Bjørn Mork bjorn at mork.no
Mon Jul 30 08:19:12 EDT 2018

Torbjorn Jansson <torbjorn.jansson at mbox200.swipnet.se> writes:
> On 2018-05-01 12:17, Bjørn Mork wrote:
>> John Crispin <john at phrozen.org> writes:
>>> making gmac2 work s not trivial with the current driver.
>> Thanks for confirming.  Then I guess I can just wrap up what I have and
>> make it public.  Just want to figure out how the LEDs are connected
>> first. Bootloader initiated blinking patterns are persistent, so I'm
>> guessing some I2C(?) connected controller.  Or something..
>>> however making the upstream mtk_eth_soc driver work on mt7621 is
>>> pretty easy i think and will give you dual gmac support. upstream only
>>> supports mt7623 arm atm. its been on my todo list for a while but i
>>> simply have not been able to find the 2-3 days required to make it
>>> work.
>> I wish I could help. But I have enough self-insight to realize that it
>> is way beyond my capabilities, after a quick look at the driver.
>> Bjørn
> sorry for reviving old mail thread but just out of curiosity, will
> this help the ubiquiti edgerouter x sfp with getting the sfp port
> working too?
> it is also an mt7621.

I would guess yes.  But I might be wrong.  I am not sure I understand
the high level block diagrams I've seen correctly.

My understanding is that the MT7621 has 2 CPU GMACs, a 7 port switch, 5
PHYs and 1 set of RGMII pads.  The first GMAC is always connected to the
switch. The second GMAC can be connected either to the switch or to the
RGMII pads.  If this is correct then I would assume that a design with
an SFP cage would use some external PHY with SERDES, connected to the
second GMAC using the RGMII pads.

But it would be good to have someone with a clue confirm or refute

The WiFi extender I am having trouble with (ZyXEL WAP6805 - similar to
the WAP6806) has an RGMII connected Quantenna 5Ghz module.  My
assumption is that this module is connected to the RGMII pads on the
MT7621 and that I need support for the second GMAC to get it running.
The Quantenna module loads its firmware using TFTP in the OEM firmware.

I note that forum user Thirsty has had some success using the mainline
MT7623 driver to enable both GMACs:

but this currently implies DSA, so it's not exactly plug-and-play with
OpenWrt.  I haven't tried it myself yet.


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