netdev - Re: [REGRESSION] net: pcs-lynx: 10G SFP no longer links up

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Message-Id: <2d709754-3d4a-4803-b86f-9efa2a6bf655@app.fastmail.com>
Date: Thu, 10 Jul 2025 15:29:01 +1000
From: "Mathew McBride" <matt@...verse.com.au>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: netdev@...r.kernel.org, regressions@...ts.linux.dev
Subject: Re: [REGRESSION] net: pcs-lynx: 10G SFP no longer links up

Hi Russell,

On Wed, Apr 23, 2025, at 7:01 PM, Mathew McBride wrote:
> 
[snip]

Just following up on this issue where directly connected SFP+ modules stopped linking up after the introduction of in-band capabilities.

The diff you provided below[1] resolved the issue. 
Were you planning on submitting it as a patch? If not, I'd be happy to send it in.

Best Regards,
Matt

[1] https://lore.kernel.org/all/aAe94Tkf-IYjswfP@shell.armlinux.org.uk/
> Thanks Russell!
> 
> The diff below does fix the problem, 10G SFP's now link up again.
> 
> I should note that Alex Guzman was the one who originally reported the issue to me, he has also confirmed this diff resolves the issue.
> Link: https://forum.traverse.com.au/t/sfp-ports-stop-working-with-linux-6-14-in-arch-linux/1076/4
> 
> > Please try the diff below:
> > 
> > diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
> > index 1bdd5d8bb5b0..2147e2d3003a 100644
> > --- a/drivers/net/phy/phylink.c
> > +++ b/drivers/net/phy/phylink.c
> > @@ -3624,6 +3624,15 @@ static int phylink_sfp_config_optical(struct phylink *pl)
> > phylink_dbg(pl, "optical SFP: chosen %s interface\n",
> >     phy_modes(interface));
> >  
> > + /* GBASE-R interfaces with the exception of KR do not have autoneg at
> > + * the PCS. As the PCS is media facing, disable the Autoneg bit in the
> > + * advertisement.
> > + */
> > + if (interface == PHY_INTERFACE_MODE_5GBASER ||
> > +     interface == PHY_INTERFACE_MODE_10GBASER ||
> > +     interface == PHY_INTERFACE_MODE_25GBASER)
> > + __clear_bit(ETHTOOL_LINK_MODE_Autoneg_BIT, config.advertising);
> > +
> > if (!phylink_validate_pcs_inband_autoneg(pl, interface,
> > config.advertising)) {
> > phylink_err(pl, "autoneg setting not compatible with PCS");
> > 
> > -- 
> > RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
> > FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
> > 
>