linux-kernel - Re: [PATCH net-next 2/2] net: phy: aquantia: allow forcing order of MDI pairs

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Message-ID: <71391388-4c18-4239-b74d-807dfc48bbc5@lunn.ch>
Date: Fri, 23 Aug 2024 03:28:39 +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 2/2] net: phy: aquantia: allow forcing order of
 MDI pairs

On Wed, Aug 21, 2024 at 05:18:44PM +0100, Daniel Golle wrote:
> On Wed, Aug 21, 2024 at 06:07:06PM +0200, Andrew Lunn wrote:
> > On Wed, Aug 21, 2024 at 01:46:50PM +0100, Daniel Golle wrote:
> > > Normally, the MDI reversal configuration is taken from the MDI_CFG pin.
> > > However, some hardware designs require overriding the value configured
> > > by that bootstrap pin. The PHY allows doing that by setting a bit which
> > > allows ignoring the state of the MDI_CFG pin and configuring whether
> > > the order of MDI pairs should be normal (ABCD) or reverse (DCBA).
> > > 
> > > Introduce two boolean properties which allow forcing either normal or
> > > reverse order of the MDI pairs from DT.
> > 
> > How does this interact with ethtool -s eth42 [mdix auto|on|off]
> > 
> > In general, you want mdix auto, so the two ends figure out how the
> > cable is wired and so it just works.
> 
> It looks like Aquantia only supports swapping pair (1,2) with pair (3,6)
> like it used to be for MDI-X on 100MBit/s networks.
> 
> When all 4 pairs are in use (for 1000MBit/s or faster) the link does not
> come up with pair order is not configured correctly, either using MDI_CFG
> pin or using the "PMA Receive Reserved Vendor Provisioning 1" register.
> 
> And yes, I did verify that Auto MDI-X is enabled in the
> "Autonegotiation Reserved Vendor Provisioning 1" register.

Is it possible to read the strap configuration?  All DT needs to
indicate is that the strap is inverted.

	Andrew