Re: [net-next RFC PATCH 03/14] dt-bindings: net: document ethernet PHY package nodes

[Robert Marko]

On Fri, Nov 24, 2023 at 4:16 PM Russell King (Oracle)
<linux@xxxxxxxxxxxxxxx> wrote:
>
> On Fri, Nov 24, 2023 at 03:44:20PM +0100, Andrew Lunn wrote:
> > >             First Serdes mode       Second Serdes mode
> > > Option 1    PSGMII for copper       Disabled
> > >             ports 0-4
> > > Option 2    PSGMII for copper       1000BASE-X / 100BASE-FX
> > >             ports 0-4
> > > Option 3    QSGMII for copper       SGMII for
> > >             ports 0-3               copper port 4
> >
> > With option 2, can the second SERDES also do SGMII? You are likely to
> > need that when a Copper SFP module is inserted into the cage.
>
> The document states "The fiber port supports 1000BASE-X/100BASE-FX".
>
> The same is true of Marvell 88x3310's fiber port - it supports only
> fiber not SGMII. This is actually something else that - when the
> patches for stacked PHYs mature - will need to be addressed. If we
> have a 1G copper SFP plugged into an interface that only supports
> 1000base-X then we need a way to switch the PHY on the SFP module
> to 1000base-X if it's in SGMII mode.
>
> Some copper SFPs come up in 1000base-X mode, and we currently rely
> on the 88e1111 driver to switch them to SGMII mode. Others do want
> SGMII mode (like Mikrotik RJ01 where the PHY is inaccessible and
> thus can't be reconfigured.)

I can confirm that SGMII mode doesn't work with Option 2, I have tested this
a while ago with Mikrotik RJ01 (I think it has AR803x, but its not accessible as
you pointed out) and it was somewhat working but in half duplex only
and dropping
packets.
Currently, SFP mode is checked and only 1000Base-X and 100Base-FX are
accepted, otherwise the module insert will return and error for unsupported
mode.

Regards,
Robert

>
> --
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-- 
Robert Marko
Staff Embedded Linux Engineer
Sartura Ltd.
Lendavska ulica 16a
10000 Zagreb, Croatia
Email: robert.marko@xxxxxxxxxx
Web: www.sartura.hr