linux-kernel - Re: [PATCH net-next v2 7/9] net: phy: introduce ethtool_phy

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Message-ID: <6bdaf8de-8f7e-42db-8c29-1e8a48c4ddda@lunn.ch>
Date: Mon, 7 Oct 2024 15:01:50 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc: "Russell King (Oracle)" <linux@...linux.org.uk>, davem@...emloft.net,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	thomas.petazzoni@...tlin.com, Jakub Kicinski <kuba@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	linux-arm-kernel@...ts.infradead.org,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Herve Codina <herve.codina@...tlin.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Vladimir Oltean <vladimir.oltean@....com>,
	Marek Behún <kabel@...nel.org>,
	Köry Maincent <kory.maincent@...tlin.com>,
	Oleksij Rempel <o.rempel@...gutronix.de>
Subject: Re: [PATCH net-next v2 7/9] net: phy: introduce ethtool_phy_ops to
 get and set phy configuration

> It seems I am missing details in my cover and the overall work I'm
> trying to achieve.
> 
> This series focuses on isolating the PHY in the case where only one
> PHY is attached to the MAC.

I can understand implementing building blocks, but this patchset seems
to be more than that, it seems to be a use case of its own. But is
isolating a single PHY a useful use case? Do we want a kAPI for this?

> I have followup work to support multi-PHY
> interfaces. I will do my best to send the RFC this week so that you can
> take a look. I'm definitely not saying the current code supports that.
> 
> To tell you some details, it indeed works as Russell says, I
> detach/re-attach the PHYs, ndev->phydev is the "currently active" PHY.
> 
> I'm using a new dedicated "struct phy_mux" for that, which has :
> 
>  - Parent ops (that would be filled either by the MAC, or by phylink,
> in the same spirit as phylink can be an sfp_upstream), which manages
> PHY attach / detach to the netdev, but also the state-machine or the
> currently inactive PHY.
> 
>  - multiplexer ops, that implement the switching logic, if any (drive a
> GPIO, write a register, this is in the case of real multiplexers like
> we have on some of the Turris Omnia boards, which the phy_mux framework
> would support)
> 
>  - child ops, that would be hooks to activate/deactivate a PHY itself
> (isoalte/unisolate, power-up/power-down).

Does the kAPI for a single PHY get used, and extended, in this setup?

> I'll send the RFC ASAP, I still have a few rough edges that I will
> mention in the cover.
> 
> > However, I still want to hear whether multiple PHYs can be on the same
> > MII bus from a functional electrical perspective.
> 
> Yup, I have that hardware.

Can you talk a bit more about that hardware? What PHYs do you have?
What interface modes are they using?

	Andrew