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

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Message-ID: <6455123a-6785-4173-b145-3a1a3eb48175@leemhuis.info>
Date: Tue, 12 Aug 2025 14:17:39 +0200
From: Thorsten Leemhuis <regressions@...mhuis.info>
To: Mathew McBride <matt@...verse.com.au>,
 "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

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.

Ciao, Thorsten

> [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!
>>>
>>
> 
>