RE: [PATCH net-next 4/5] onsemi: ncn260xx: Add driver support for NCN26010 and TS2500 MAC-PHY

[Selvamani Rajagopal]

> -----Original Message-----
> From: Selvamani Rajagopal
> Sent: Monday, May 4, 2026 12:18 PM
> To: 'Andrew Lunn' <andrew@xxxxxxx>
> Cc: Piergiorgio Beruto <Pier.Beruto@xxxxxxxxxx>; andrew+netdev@xxxxxxx;
> davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx; pabeni@xxxxxxxxxx;
> netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: RE: [PATCH net-next 4/5] onsemi: ncn260xx: Add driver support for NCN26010
> and TS2500 MAC-PHY
> 
> 
> 
> > -----Original Message-----
> > From: Andrew Lunn <andrew@xxxxxxx>
> > Sent: Monday, May 4, 2026 12:15 PM
> > To: Selvamani Rajagopal <Selvamani.Rajagopal@xxxxxxxxxx>
> > Cc: Piergiorgio Beruto <Pier.Beruto@xxxxxxxxxx>; andrew+netdev@xxxxxxx;
> > davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx;
> pabeni@xxxxxxxxxx;
> > netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> > Subject: Re: [PATCH net-next 4/5] onsemi: ncn260xx: Add driver support for NCN26010
> > and TS2500 MAC-PHY
> >
> >
> > This Message Is From an External Sender
> > This message came from outside your organization.
> >
> > > > So you seem to be compliant with the standard. I've not seen anything
> > > > use MDIO_MMD_POWER_UNIT so not having that should not be an
> > > > issue. MDIO_MMD_AN is used by a number of PHYs, but i assume yours
> > > > does not.
> > > >
> > > > 802.3 C45 says that if a register does not exist, it should read
> > > > 0. What would happen if a read was made to
> > > > OA_TC6_PHY_C45_AUTO_NEG_MMS5, rather than returning EOPNOTSUPP?
> > > >
> > > > Table 6 says nothing about MMD 30, which you map to 12. 10-15 are
> > > > defined as vendor specific, so that is O.K.
> > > >
> > > > But can we simply this. Add something like
> > > >
> > > > void oa_tc6_set_vend1_mms(struct oa_tc6 *tc6, int mms)
> > > > {
> > > > tc6->vend1_mms = mms;
> > > > }
> > > >
> > > > and make oa_tc6_get_phy_c45_mms() look at its value?
> > >
> > > Sure. I can do that.
> > >
> > > Since we don't support PCS, and POWER_UNIT, may I suggest alternative solution?
> >
> > I would prefer to rely on 802.3 defined C45 behaviour. A read to a
> > register which does not exists gives 0. That is what PHYs and phylib
> > expect.
> >
> > You failed to answer my question about this. What happens with your
> > device if you access C45 registers which don't exist?
> 
> Sorry. Waiting for an answer from hardware designer.


It is confirmed that we will return 0 if unsupported registers are read.

> 
> >
> > > This gives flexibility to vendors as mostly likely, all the vendors
> > > may not share the same set of MDIO_MMD_XXX support.
> >
> > Well, all vendors should support what is defined in the standard. It
> > is only MDIO_MMD_VEND1 which is left undefined, and different vendors
> > could put that at different MMS in the 10-15 range, but i think the
> > rest is well defined.
> >
> > Andrew