linux-kernel - Re: [PATCH net-next v2 1/2] dt-bindings: net: ethernet-phy: Add master-slave role property for SPE PHYs

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Message-ID: <443a53a5-71ac-4287-9951-df3c54b11b8d@lunn.ch>
Date: Wed, 11 Sep 2024 14:05:29 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Rob Herring <robh@...nel.org>
Cc: Oleksij Rempel <o.rempel@...gutronix.de>,
	Heiner Kallweit <hkallweit1@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Florian Fainelli <f.fainelli@...il.com>, kernel@...gutronix.de,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	Russell King <linux@...linux.org.uk>, devicetree@...r.kernel.org
Subject: Re: [PATCH net-next v2 1/2] dt-bindings: net: ethernet-phy: Add
 master-slave role property for SPE PHYs

> It seems silly to maintain both forever. I'd rather have one or the
> other than both.

It currently seems like 802.3 is going to keep with master/slave in
the body of the text. And they don't even have to deal with breaking
backwards compatibility. So i suggest we keep with master/slave, but
comment that an annex of the standard proposes alternative names of
leader/follower. But don't actually accept them.

> 
> > As to you comment about it being unclear what it means i would suggest
> > a reference to 802.3 section 1.4.389:
> >
> >   1.4.389 master Physical Layer device (PHY): Within IEEE 802.3, in a
> >   100BASE-T2, 1000BASE-T, 10BASE-T1L, 100BASE-T1, 1000BASE-T1, or any
> >   MultiGBASE-T link containing a pair of PHYs, the PHY that uses an
> >   external clock for generating its clock signals to determine the
> >   timing of transmitter and receiver operations. It also uses the
> >   master transmit scrambler generator polynomial for side-stream
> >   scrambling. Master and slave PHY status is determined during the
> >   Auto-Negotiation process that takes place prior to establishing the
> >   transmission link, or in the case of a PHY where Auto-Negotiation is
> >   optional and not used, master and slave PHY status
> 
> phy-status? Shrug.

phy-status is too generic. Maybe 'timing-role' ?

> 
> Another thought. Is it possible that h/w strapping disables auto-neg,
> but you actually want to override that and force auto-neg?

Autoneg can be used for a bunch of parameters. In automotive
situations, it is generally disabled and those parameters are
forced. In more tradition settings those parameters are
negotiated. However, even with autoneg enabled, you can force each
individual parameter, rather than negotiate it.

So we would need a DT parameter about autoneg in general. And then a
DT parameter about 'timing-role', where force-master/force-slave means
don't negotiate, and prefer-master/prefer-slave means do negotiate
with the given preference.

	Andrew