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

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Message-ID: <aJ8JezoKkgKLoRCR@shell.armlinux.org.uk>
Date: Fri, 15 Aug 2025 11:18:35 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Thorsten Leemhuis <regressions@...mhuis.info>
Cc: Mathew McBride <matt@...verse.com.au>, netdev@...r.kernel.org,
	regressions@...ts.linux.dev
Subject: Re: [REGRESSION] net: pcs-lynx: 10G SFP no longer links up

On Tue, Aug 12, 2025 at 05:42:59PM +0100, Russell King (Oracle) wrote:
> On Tue, Aug 12, 2025 at 02:17:39PM +0200, Thorsten Leemhuis wrote:
> > Lo!
> > 
> > On 10.07.25 07:29, Mathew McBride wrote:
> > > 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.
> > 
> > I might be missing something, but from here it looks like it fall
> > through the cracks on Russell's side. This is nothing bad, this can
> > happen, especially during summer and thus vacation time. I'd thus say:
> > wait two or three days if this reminds him of the patch, otherwise go
> > ahead and submit it yourself to get the regression fixed.
> 
> Yes, the reminder was sent during July when I wasn't looking at email,
> and as you can imagine, if I spend three weeks on vacation, I am _not_
> going to catch up with that pile of email - if I were, there'd be no
> point taking vacation because the mental effort would be just the same
> as having no vacation.
> 
> I have been debating whether we should actually do something like this,
> especially given the issues with 2500base-X:
> 
> -       if (!phylink_validate_pcs_inband_autoneg(pl, interface,
> -                                                config.advertising)) {
> -               phylink_err(pl, "autoneg setting not compatible with PCS");
> -               return -EINVAL;
> +       while (!phylink_validate_pcs_inband_autoneg(pl, interface,
> +                                                   config.advertising)) {
> +               if (!test_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
> +                             config.advertising)) {
> +                       phylink_err(pl, "autoneg setting is not compatible with PCS");
> +                       return -EINVAL;
> +               }
> +
> +               __clear_bit(ETHTOOL_LINK_MODE_Autoneg_BIT, config.advertising);
>         }
> 
> which turns it into something generic - but my problem with that is..
> what if the module (e.g. a GPON module immitating a fibre module)
> requires Autoneg but the PCS doesn't support Autoneg for the selected
> interface mode.

Please note that I'm waiting for a response from those who have the
problem... and this thread is again getting buried, so likely I'll
forget about it soon.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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