netdev - Re: [PATCH net-next 1/2] dt-bindings: net: marvell,aquantia: add properties to override MDI

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Message-ID: <6e018572-0a74-40af-bf5d-74aed60853a6@lunn.ch>
Date: Wed, 21 Aug 2024 18:13:56 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Daniel Golle <daniel@...rotopia.org>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	Christian Marangi <ansuelsmth@...il.com>,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	Robert Marko <robimarko@...il.com>,
	Russell King <rmk+kernel@...linux.org.uk>,
	Chad Monroe <chad.monroe@...ran.com>,
	John Crispin <john@...ozen.org>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 1/2] dt-bindings: net: marvell,aquantia: add
 properties to override MDI_CFG

On Wed, Aug 21, 2024 at 05:08:39PM +0100, Daniel Golle wrote:
> On Wed, Aug 21, 2024 at 06:00:36PM +0200, Andrew Lunn wrote:
> > On Wed, Aug 21, 2024 at 01:46:30PM +0100, Daniel Golle wrote:
> > > Usually the MDI pair order reversal configuration is defined by
> > > bootstrap pin MDI_CFG. Some designs, however, require overriding the MDI
> > > pair order and force either normal or reverse order.
> > 
> > Could you explain that in a bit more detail. Are you talking about
> > changing the order of the 4 pairs? Or reversing the polarity within
> > pairs?
> 
> It's about changing the order of the 4 pairs, either ABCD or DCBA.
> Polarity of each pair is not affected by this.

So when i do

ethtool -s 42 mdix off

to enable straight through, are you saying the PHY actually does
crossover, because the pull-up tells it the wrong thing about how the
cable is wired? And `mdix on` for crossover gives straight?

'mdix auto' just works as expected, since it tried all the
combinations until it works?

      Andrew