linux-kernel - Re: [PATCH net-next v3 2/2] net: phy: aquantia: allow forcing order of MDI pairs

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Message-ID: <c5339983-d768-4a1c-a951-dbc99ae16b21@lunn.ch>
Date: Tue, 8 Oct 2024 23:13:57 +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>,
	Paweł Owoc <frut3k7@...il.com>,
	netdev@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 2/2] net: phy: aquantia: allow forcing order
 of MDI pairs

On Fri, Oct 04, 2024 at 05:18:16PM +0100, Daniel Golle wrote:
> Despite supporting Auto MDI-X, 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.
> 
> Normally, the order of MDI pairs being either ABCD or DCBA is configured
> by pulling 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 in
> "PMA Receive Reserved Vendor Provisioning 1" register which allows
> ignoring the state of the MDI_CFG pin and another bit configuring
> whether the order of MDI pairs should be normal (ABCD) or reverse
> (DCBA). Pair polarity is not affected and remains identical in both
> settings.
> 
> Introduce property "marvell,mdi-cfg-order" which allows forcing either
> normal or reverse order of the MDI pairs from DT.
> 
> If the property isn't present, the behavior is unchanged and MDI pair
> order configuration is untouched (ie. either the result of MDI_CFG pin
> pull-up/pull-down, or pair order override already configured by the
> bootloader before Linux is started).
> 
> Forcing normal pair order is required on the Adtran SDG-8733A Wi-Fi 7
> residential gateway.
> 
> Signed-off-by: Daniel Golle <daniel@...rotopia.org>

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew