netdev - Re: net: phy: Dealing with 88e1543 dual-port mode

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Date:   Thu, 19 Nov 2020 16:45:44 +0100
From:   Maxime Chevallier <maxime.chevallier@...tlin.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Antoine Tenart <atenart@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: net: phy: Dealing with 88e1543 dual-port mode

Hi Andrew,

On Thu, 19 Nov 2020 16:16:41 +0100
Andrew Lunn <andrew@...n.ch> wrote:

>Hi Maxime
>
>> The way this works is that the PHY is internally configured by chaining
>> 2 internal PHYs back to back. One PHY deals with the Host interface and
>> is configured as an SGMII to QSGMII converter (the QSGMII is only used
>> from within the PHY), and the other PHY acts as the Media-side PHY,
>> configured in QSGMII to auto-media (RJ45 or Fiber (SFP)) :
>> 
>>                 +- 88e1543 -----------------------+
>> +-----+         | +--------+          +--------+  |  /-- Copper (RJ45)
>> |     |--SGMII----| Port 0 |--QSGMII--| Port 1 |----<
>> |     |         | +--------+          +--------+  |  \--- Fiber
>> | MAC |         |                                 |
>> |     |         | +--------+          +--------+  |  /-- Copper (RJ45)
>> |     |--SGMII----| Port 2 |--QSGMII--| Port 3 |----<
>> +-----+         | +--------+          +--------+  |  \-- Fiber
>>                 +---------------------------------+  
>
>Does this mean you need a dual port MAC as well?
>
>Do we need to configure the MUX in the MAC?

No, it's my schematic that is misleading in that case :) The 2
ports are independent of each other. There isn't any configuration on
the MAC part for that setup.

Thanks,

Maxime



-- 
Maxime Chevallier, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com