netdev - Re: [PATCH net-next 3/3] selftests: mlxsw: Add speed and auto-negotiation test

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Message-ID: <20190611063526.GA6167@splinter>
Date:   Tue, 11 Jun 2019 09:35:26 +0300
From:   Ido Schimmel <idosch@...sch.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, amitc@...lanox.com,
        mlxsw@...lanox.com, Ido Schimmel <idosch@...lanox.com>
Subject: Re: [PATCH net-next 3/3] selftests: mlxsw: Add speed and
 auto-negotiation test

On Mon, Jun 10, 2019 at 04:06:33PM +0200, Andrew Lunn wrote:
> On Mon, Jun 10, 2019 at 04:58:48PM +0300, Ido Schimmel wrote:
> > On Mon, Jun 10, 2019 at 03:48:20PM +0200, Andrew Lunn wrote:
> > > > +		# Skip 56G because this speed isn't supported with autoneg off.
> > > > +		if [[ $speed == 56000 ]]; then
> > > > +			continue
> > > > +		fi
> > > 
> > > Interesting. How is 56000 represented in ethtool? Listed in both
> > > "Supported link modes" and "Advertised link modes"?
> > 
> > Hi Andrew,
> > 
> > Yes. We recently sent a patch to error out if autoneg is off: Commit
> > 275e928f1911 ("mlxsw: spectrum: Prevent force of 56G").
> 
> I never get access to high speed links like this. Do you have a
> reference to why 56G needs auto-neg? What makes it different to every
> other link mode?

Hi Andrew,

I verified with PHY engineers and this limitation is specific to our
hardware, so no external reference I can provide.