Subject: Re: [PATCH net-next 5/5] net: dsa: b53: Add SerDes support

From: Andrew Lunn <[email-masked]>
Date: Wed, 5 Sep 2018 02:06:28 +0200

On Tue, Sep 04, 2018 at 04:55:26PM -0700, Florian Fainelli wrote:
> On 09/04/2018 04:32 PM, Andrew Lunn wrote:
> > 
> > 
> >> +void b53_serdes_phylink_validate(struct b53_device *dev, int port,
> >> +				 unsigned long *supported,
> >> +				 struct phylink_link_state *state)
> >> +{
> >> +	u8 lane = b53_serdes_map_lane(dev, port);
> >> +
> >> +	if (lane == B53_INVALID_LANE)
> >> +		return;
> >> +
> >> +	switch (lane) {
> >> +	case 0:
> >> +		phylink_set(supported, 2500baseX_Full);
> > 
> > Hi Florian
> > 
> > Could you also use it for 2500BaseT_Full with an appropriate copper
> > PHY?
> 
> My reading of the datasheet (which only mentions 2.5G with no further
> mention) make me think that is not possible to do copper at 2.5G and
> only 2500baseX since it only talks about fiber and not copper.
> 
> Would you recommend a specific SFP that allows that? Like this one:
> 
> https://www.flexoptix.net/en/sfp-t-transceiver-2h-gigabit-cat-5e-rj-45-100m-100m-1000m-2500-base-t.html?co8829=85744

I was actually thinking of a 'plain old' copper PHY with a SERDES
interface which can do 25000Base-T. The Marvell 88x3310 or the
Aquantia 10G PHY, for example.

Russell might be able to make a recommendation. I don't have any
Copper SFP modules.

       Andrew