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

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Date:   Sat, 2 Mar 2019 21:36:01 +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 21:34, Heiner Kallweit wrote:
> 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.
>>
What I forgot: I can't explain why your SFP use case works. Was it also
with this Marvell switch? 

> 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
> 
Heiner