netdev - Re: [net-next PATCH v3 11/15] eth: fbnic: Add link detection

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Message-ID: <CAKgT0UfbUrVR6U-cbNxufQ0MN9Cna0tdC6dPMBJRAHSdj5=C8Q@mail.gmail.com>
Date: Tue, 2 Jul 2024 13:59:41 -0700
From: Alexander Duyck <alexander.duyck@...il.com>
To: Andrew Lunn <andrew@...n.ch>
Cc: "Russell King (Oracle)" <linux@...linux.org.uk>, netdev@...r.kernel.org, 
	Alexander Duyck <alexanderduyck@...com>, kuba@...nel.org, davem@...emloft.net, 
	pabeni@...hat.com, edumazet@...gle.com, kernel-team@...a.com
Subject: Re: [net-next PATCH v3 11/15] eth: fbnic: Add link detection

On Tue, Jul 2, 2024 at 1:37 PM Andrew Lunn <andrew@...n.ch> wrote:
>
> > > As for multiple PCS for one connection, is this common, or special to
> > > your hardware?
> >
> > I would think it is common. Basically once you get over 10G you start
> > seeing all these XXXXXbase[CDKLS]R[248] speeds advertised and usually
> > the 2/4/8 represents the number of lanes being used. I would think
> > most hardware probably has a PCS block per lane as they can be
> > configured separately and in our case anyway you can use just the one
> > lane mode and then you only need to setup 1 lane, or you can use the 2
> > lane mode and you need to setup 2.
> >
> > Some of our logic is merged like I mentioned though so maybe it would
> > make more sense to just merge the lanes. Anyway I guess I can start
> > working on that code for the next patch set. I will look at what I
> > need to do to extend the logic. For now I might be able to get by with
> > just dropping support for 50R1 since that isn't currently being used
> > as a default.
>
> So maybe a dumb question. How does negotiation work? Just one performs
> negotiation? They all do, and if you get different results you declare
> the link broken? First one to complete wins? Or even, you can
> configure each lane to use different negotiation parameters...
>
>     Andrew

My understanding is that auto negotiation is done at 10G or 25G so
that is with only one PCS link enabled if I am not mistaken.

Admittedly we haven't done the autoneg code yet so I can't say for
certain. I know the hardware was tested with the driver handling the
link after the fact, but I don't have the code in the driver for
handling the autoneg yet since we don't use that in our datacenter.

- Alex