netdev - Re: SFP: Copper module with different PHY address (Netgear AGM734)

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Message-ID: <d4d526db-995b-4426-8a8d-b53acceb5f74@lunn.ch>
Date:   Wed, 26 Apr 2023 19:04:47 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Andreas Böhler <news@...ehler.at>
Cc:     netdev@...r.kernel.org, Russell King <rmk+kernel@...linux.org.uk>
Subject: Re: SFP: Copper module with different PHY address (Netgear AGM734)

On Wed, Apr 26, 2023 at 06:47:33PM +0200, Andreas Böhler wrote:
> Hi,
> 
> I have a bunch of Netgear AGM734 copper SFP modules that I would like to use
> with my switches. Upon insertion, a message "no PHY detected" pops up.
> 
> Upon further investigation I found out that the Marvell PHY in these modules
> is at 0x53 and not at the expected 0x56. A quick check with a changed
> SFP_PHY_ADDR works as expected.
> 
> Which is the best scenario to proceed?
> 
> 1. Always probe SFP_PHY_ADDR and SFP_PHY_ADDR - 3
> 
> 2. Create a fixup for this specific module to probe at a different address.
> However, I'm afraid this might break "compatible" modules.
> 
> 3. Something else?

Hi Andreas

It is a good idea to Cc: the SFP and PHY Maintainers.

What does ethtool -m show?

Is there something we a key a quirk off?

Is it a true Netgear SFP?

There are OEMs which will load there EEPROM to emulate other
vendors. e.g.:

https://edgeoptic.com/products/netgear/agm734/

   Andrew