netdev - RE: [EXTERNAL] Re: [PATCH net-next] net: marvell: prestera: fix FEC error message for SFP ports

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Message-ID:
 <BL1PR18MB4248EFE8E7D182A5601927E1DB98A@BL1PR18MB4248.namprd18.prod.outlook.com>
Date: Wed, 4 Feb 2026 13:13:31 +0000
From: Elad Nachman <enachman@...vell.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: Jonas Gorski <jonas.gorski@...il.com>,
        Alok Tiwari
	<alok.a.tiwari@...cle.com>,
        "Taras Chornyi [C]" <tchornyi@...vell.com>,
        "Volodymyr Mytnyk [C]" <vmytnyk@...vell.com>,
        Yevhen Orlov
	<yevhen.orlov@...ision.eu>,
        "Vadym Kochan [C]" <vkochan@...vell.com>,
        Taras
 Chornyi <taras.chornyi@...ision.eu>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "davem@...emloft.net"
	<davem@...emloft.net>,
        "andrew+netdev@...n.ch" <andrew+netdev@...n.ch>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "alok.a.tiwarilinux@...il.com" <alok.a.tiwarilinux@...il.com>
Subject: RE: [EXTERNAL] Re: [PATCH net-next] net: marvell: prestera: fix FEC
 error message for SFP ports

Hi,

> 
> 
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Wednesday, February 4, 2026 5:15 AM
> To: Elad Nachman <enachman@...vell.com>
> Cc: Jonas Gorski <jonas.gorski@...il.com>; Alok Tiwari <alok.a.tiwari@...cle.com>; Taras Chornyi [C] <tchornyi@...vell.com>; Volodymyr Mytnyk [C] <vmytnyk@...vell.com>; Yevhen Orlov <yevhen.orlov@...ision.eu>; Vadym Kochan [C] <vkochan@...vell.com>; Taras Chornyi <taras.chornyi@...ision.eu>; pabeni@...hat.com; edumazet@...gle.com; davem@...emloft.net; andrew+netdev@...n.ch; netdev@...r.kernel.org; alok.a.tiwarilinux@...il.com
> Subject: [EXTERNAL] Re: [PATCH net-next] net: marvell: prestera: fix FEC error message for SFP ports
> On Mon, 2 Feb 2026 11:26:00 +0100 Jonas Gorski wrote:
> 
> > On 02/02/2026 06:28, Alok Tiwari wrote:
> > > In prestera_ethtool_set_fecparam(), the error message is opposite of
> > > the condition checking PRESTERA_PORT_TCVR_SFP. FEC configuration is
> > > not allowed on SFP ports, but the message says "non-SFP ports", which
> > > does not match the condition.
> > >
> > > diff --git a/drivers/net/ethernet/marvell/prestera/prestera_ethtool.c b/drivers/net/ethernet/marvell/prestera/prestera_ethtool.c
> > > index 2f52daba58e6..a259da9f30f4 100644
> > > --- a/drivers/net/ethernet/marvell/prestera/prestera_ethtool.c
> > > +++ b/drivers/net/ethernet/marvell/prestera/prestera_ethtool.c
> > > @@ -718,7 +718,7 @@ static int prestera_ethtool_set_fecparam(struct net_device *dev,
> > >  	}
> > >
> > >  	if (port->caps.transceiver == PRESTERA_PORT_TCVR_SFP) {
> > > -		netdev_err(dev, "FEC set is not allowed on non-SFP ports\n");
> > > +		netdev_err(dev, "FEC set is not allowed on SFP ports\n");
> > >  		return -EINVAL;
> > >  	}
> > >
> >
> > I'm pretty sure that the condition here is wrong, not the error message.
> >
> > AFAIK it doesn't make sense to configure FEC on ethernet/copper ports,
> > but for SFP ports, it may be required depending on the transceiver or
> > cable used, especially for fiber modules.
> >
> > I may be wrong though.
> >
> > This check was introduced with bb5dbf2cc64d ("net: marvell: prestera:
> > add firmware v4.0 support"), but that commit does not offer any
> > explanation for it in the commit message.
> 
> Elad, could you clarify this? A bit hard to tell whether CR is included
> in "SFP" from glancing at the code.

Basically, the supported devices have FEC on 10G-BASE-KR and upwards (CR: from 40G-BASE-CR),
and for USXGMII SERDES, which drives multiple copper PHYs.

Judging based on all of the above,
I think it is best to remove this check (plus said error message) altogether and let the firmware return an error if the mode/speed/FEC combination is invalid.

FYI,

Elad.