netdev - Re: [PATCH net-next] net: dsa: mv88e6xxx: support in-band signalling with external PHY for 1000BaseX/2500BaseX

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Message-ID: <dd84d667-ecc6-046d-00e3-9205fa8ec2bd@gmail.com>
Date:   Sat, 2 Mar 2019 21:34:12 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        David Miller <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] net: dsa: mv88e6xxx: support in-band signalling
 with external PHY for 1000BaseX/2500BaseX

On 02.03.2019 21:13, Andrew Lunn wrote:
> On Sat, Mar 02, 2019 at 04:57:32PM +0100, Heiner Kallweit wrote:
>> Propagate the external PHY settings also in 1000BaseX and
>> 2500BaseX mode.
> 
> Hi Heiner
> 
Hi Andrew

> I don't think this is needed. 1000BaseX and 2500BaseX does not support
> inband signalling. So the mac_config() call for these modes should
> include the needed speed configuration. I've used 1000BaseX with an
> SFP and there was no need to configure anything.
> 
1000BaseX and 2500BaseX use 802.3z Clause 37 inband auto-neg. From what
I've read 1000BaseT is an extension of it.
My understanding is that w/o such inband signalling we had no chance
to detect a "link up" situation. All we could detect is: serial connection
is synced. Also my understanding is that the ACK to this inband signalling
triggers the "link up" interrupt.

Here I found something:
http://www.methode.com/Documents/TechnicalLibrary/SFP_Ethernet_Auto_Negotiation.pdf

I briefly looked at the SFP connector and there don't seem to be pins for
out-of-band signalling. So there must be some inband signalling.

>     Andrew
> 
Heiner