linux-kernel - RE: [PATCH] ixgbe: Manual AN-37 for troublesome link partners for X550 SFI

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Message-ID:
 <VI1PR04MB5501C2A00D658115EF4E7845EA9E2@VI1PR04MB5501.eurprd04.prod.outlook.com>
Date: Fri, 6 Sep 2024 20:49:15 +0000
From: Jeff Daly <jeffd@...icom-usa.com>
To: Andrew Lunn <andrew@...n.ch>
CC: "anthony.l.nguyen@...el.com" <anthony.l.nguyen@...el.com>,
	"przemyslaw.kitszel@...el.com" <przemyslaw.kitszel@...el.com>,
	"davem@...emloft.net" <davem@...emloft.net>, "edumazet@...gle.com"
	<edumazet@...gle.com>, "kuba@...nel.org" <kuba@...nel.org>,
	"pabeni@...hat.com" <pabeni@...hat.com>, "intel-wired-lan@...ts.osuosl.org"
	<intel-wired-lan@...ts.osuosl.org>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] ixgbe: Manual AN-37 for troublesome link partners for
 X550 SFI

 
> On Fri, Sep 06, 2024 at 06:41:45AM -0400, Jeff Daly wrote:
> > Resubmit commit 565736048bd5 ("ixgbe: Manual AN-37 for troublesome
> > link partners for X550 SFI")
> >
> > Some (Juniper MX5) SFP link partners exhibit a disinclination to
> > autonegotiate with X550 configured in SFI mode.  This patch enables a
> > manual AN-37 restart to work around the problem.
> >
> > Resubmitted patch includes a module parameter (default disabled) to
> > isolate changes.
> 
> Module parameters are not liked in networking code. They are very user
> unfriendly, and poorly documented.

Completely understood, which is why the original patch didn't include this.

> 
> Why do you need it? Is this change risky?
> 
>         Andrew

It turns out that the patch works fine for the specific issue it's trying to address (Juniper switch), 
but for (seemingly all) other devices it breaks the autonegotiation.  A few months back it was 
reported that there were issues with Cisco switches (which we didn't have to test with).  The
parameter was added in order to isolate the specific changes from affecting any other hardware.