[EXT] Re: [PATCH v1 2/5] net: phy: marvell: extend 88E2110 to use both 2.5GHz modes

[Marek Behun]

On Wed, 24 Mar 2021 13:09:00 +0000
Stefan Chulski <stefanc at marvell.com> wrote:

> > > >
> > > > SGMII uses the same coding as 1000base-x, but the latter works only
> > > > with one speed (1000mbps), while the former can also work in 10mbps
> > > > and 100mbps (by repeating each byte 100 or 10 times, respectively).
> > > >
> > > > Then there is 2500base-x, which is the same as 1000base-x, but with
> > > > the clock being at 2.5x the speed of 1000base-x clock.
> > > >
> > > > But there is no analogue of the SGMII protocol (i.e. the repearing
> > > > of bytes in order to achieve lower speed) for the 2500base-x.
> > > >
> > > > So what I am confused about here is what is supposed to be the
> > > > difference between
> > > >   PHY_INTERFACE_MODE_SGMII_2500
> > > > and
> > > >   PHY_INTERFACE_MODE_2500BASEX
> > > > ?
> > > >
> > > > Marek  
> > 
> > I not sure what is correct naming for these mode. PHY_INTERFACE includes
> > both MAC2PHY interfaces(MII, RGMII and etc), PHY2PHY interfaces(like
> > BASEX) and SGMII(which is kind of both).
> > For both 2500BASEX and SGMII_2500 Serdes lanes set to HS-SGMII in 3.125G
> > speed, but MAC configured differently and autoneg cannot be supported.
> > 
> > Regards,
> > Stefan.  
> 
> Since we already has PHY_INTERFACE_MODE_SGMII and PHY_INTERFACE_MODE_QSGMII (5G mode), maybe we should call
> PHY_INTERFACE_MODE_HSGMII - High-Serial Gigabit Media Independent Interface (HSGMII, 3.125Gbps).

And we have now autonegotiation in this discussion. Just today I sent a
question to Marvell about 2500base-x and why inband autonegotiation is
not supported there, while it is for 1000base-x.

So are you saying that 2500base-x mode is like 1000base-x, but at 2.5g
speed, and without inband autonegotiation?

And meanwhile HS-SGMII mode is like SGMII, but at 2.5g speed, and
_WITH_ autonegotiation? And what does this autonegotiation support?
Does is support only negotiation of Pause? Or does it support
negotiation of duplexicity and speed as well?

Thank you.

Marek