netdev - Re: [PATCH] net: phy: phy_ethtool_ksettings

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Message-ID: <1ff52755-ef24-4e4b-a671-803db37b58fc@lunn.ch>
Date: Tue, 3 Dec 2024 15:45:09 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Dennis Ostermann <dennis.ostermann@...esas.com>
Cc: Russell King <linux@...linux.org.uk>,
	"nikita.yoush" <nikita.yoush@...entembedded.com>,
	Maxime Chevallier <maxime.chevallier@...tlin.com>,
	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>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Michael Dege <michael.dege@...esas.com>,
	Christian Mardmoeller <christian.mardmoeller@...esas.com>
Subject: Re: [PATCH] net: phy: phy_ethtool_ksettings_set: Allow any supported
 speed

On Tue, Dec 03, 2024 at 02:05:07PM +0000, Dennis Ostermann wrote:
> Hi,
> 
> according to IEE 802.3-2022, ch. 125.2.4.3, Auto-Negotiation is optional for 2.5GBASE-T1
> 
> > 125.2.4.3 Auto-Negotiation, type single differential-pair media
> > Auto-Negotiation (Clause 98) may be used by 2.5GBASE-T1 and 5GBASE-T1 devices to detect the
> > abilities (modes of operation) supported by the device at the other end of a link segment, determine common
> > abilities, and configure for joint operation. Auto-Negotiation is performed upon link startup through the use
> > of half-duplex differential Manchester encoding.
> > The use of Clause 98 Auto-Negotiation is optional for 2.5GBASE-T1 and 5GBASE-T1 PHYs
> 
> So, purposed change could make sense for T1 PHYs.

The proposed change it too liberal. We need the PHY to say it supports
2.5GBASE-T1, not 2.5GBASE-T. We can then allow 2.5GBASE-T1 to not use
autoneg, but 2.5GBASE-T has to use autoneg.

	Andrew