Re: [PATCH v2 1/3] net: phy: at803x: add QCA8084 ethernet phy support

[Jie Luo]

On 11/10/2023 5:33 PM, Maxime Chevallier wrote:
> On Fri, 10 Nov 2023 17:17:58 +0800
> Jie Luo <quic_luoj@xxxxxxxxxxx> wrote:
>
> > On 11/10/2023 4:53 PM, Jie Luo wrote:
> > > On 11/9/2023 5:16 PM, Maxime Chevallier wrote:
> > > > Hello,
> > > >
> > > > On Thu, 9 Nov 2023 16:32:36 +0800
> > > > Jie Luo <quic_luoj@xxxxxxxxxxx> wrote:
> > > >
> > > > [...]
> > > >   
> > > > > > What I understand from this is that this PHY can be used either as a
> > > > > > switch, in which case port 4 would be connected to the host interface
> > > > > > at up to 2.5G, or as a quad-phy, but since it uses QUSGMII the link
> > > > > > speed would be limited to 1G per-port, is that correct ?
> > > > >
> > > > > When the PHY works on the interface mode QUSGMII for quad-phy, all 4
> > > > > PHYs can support to the max link speed 2.5G, actually the PHY can
> > > > > support to max link speed 2.5G for all supported interface modes
> > > > > including qusgmii and sgmii.
> > > >
> > > > I'm a bit confused then, as the USGMII spec says that Quad USGMII really
> > > > is for quad 10/100/1000 speeds, using 10b/8b encoding.
> > > >
> > > > Aren't you using the USXGMII mode instead, which can convey 4 x 2.5Gbps
> > > >    with 66b/64b encoding ?
> > > >
> > > > Thanks,
> > > >
> > > > Maxime
> > >
> > > Hi Maxime,
> > > Yes, for quad PHY mode, it is using 66b/64 encoding.
> > >
> > > it seems that PHY_INTERFACE_MODE_USXGMII is for single port,
> > > so i take the interface name PHY_INTERFACE_MODE_QUSGMII for
> > > quad PHYs here.
> > >
> > > can we apply PHY_INTERFACE_MODE_USXGMII to quad PHYs in this
> > > case(qca8084 quad PHY mode)?
> > >
> > > Thanks,
> > > Jie.
> >
> > one more thing, if we use the PHY_INTERFACE_MODE_USXGMII for
> > the quad PHY here, the MAC serdes can't distinguish the actual
> > mode PHY_INTERFACE_MODE_USXGMII and 10G-QXGMII(qca8084 quad phy mode),
> > the MAC serdes has the different configurations for usxgmii(10g single
> > port) and qxsgmii(quad PHY).
>
> Yes you do need a way to know which mode to use, what I'm wondering is
> that the usxgmii spec actually defines something like 9 different modes
> ( 1/2/4/8 ports, with a total bandwidth ranging from 2.5Gbps to 20 Gbps
> ), should we define a phy mode for all of these variants, or should we
> have another way of getting the mode variant (like, saying I want to
> use usxgmii, in 4 ports mode, with the serdes at 10.3125Gbps).
>
> That being said, QUSGMII already exists to define a specific variant of
> USGMII, so maybe adding 10G-QXGMII is fine...

Yes, Maxime, I agree with this solution, the name 10G-QXGMII is exactly
the working mode of qca8084 quad phy mode.

> Also, net-next is still currently closed.

Ok, thanks for this reminder.