netdev - Re: [PATCH 0/2] net: phy: dp83867: add numeric impedance DT property

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Message-ID: <b7b8f855-bf38-41ba-96c4-1bdc3a1c2cc8@ti.com>
Date: Thu, 29 Jan 2026 11:31:29 -0600
From: Andrew Davis <afd@...com>
To: Teresa Remmet <t.remmet@...tec.de>, Andrew Lunn <andrew+netdev@...n.ch>,
	"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>, Andrew Lunn <andrew@...n.ch>, Heiner Kallweit
	<hkallweit1@...il.com>, Russell King <linux@...linux.org.uk>
CC: <netdev@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<upstream@...ts.phytec.de>, Yannic Moog <y.moog@...tec.de>, Benjamin Hahn
	<b.hahn@...tec.de>, Yashwanth Varakala <y.varakala@...tec.de>, Jan Remmet
	<j.remmet@...tec.de>
Subject: Re: [PATCH 0/2] net: phy: dp83867: add numeric impedance DT property

On 1/29/26 8:13 AM, Teresa Remmet wrote:
> Introduce a new way to set the output impedance over device tree.
> So far it is possible to pass the value either over an nvmem
> cell or to set the min and max booleans over device tree.
> 

We have a similar issue in our networking driver, we can either get
the MAC address though a NVMEM cell, or when that is unavailable use
fallback to using a hardcoded value in DT.

I wonder if it would make sense to add a new type of NVMEM cell that
encodes the content of the cell in DT itself..

That way we can use the same NVMEM interface in both cases, without
adding all these custom fallback properties to every NVMEM consumer.

Andrew

> In our use case we want to be able to set the impedance over
> device tree but the boolean values are not the right fit to
> provide best signal integrity for the hardware.
> 
> To: Andrew Lunn <andrew+netdev@...n.ch>
> To: David S. Miller <davem@...emloft.net>
> To: Eric Dumazet <edumazet@...gle.com>
> To: Jakub Kicinski <kuba@...nel.org>
> To: Paolo Abeni <pabeni@...hat.com>
> To: Rob Herring <robh@...nel.org>
> To: Krzysztof Kozlowski <krzk+dt@...nel.org>
> To: Conor Dooley <conor+dt@...nel.org>
> To: Andrew Davis <afd@...com>
> To: Andrew Lunn <andrew@...n.ch>
> To: Heiner Kallweit <hkallweit1@...il.com>
> To: Russell King <linux@...linux.org.uk>
> Cc: netdev@...r.kernel.org
> Cc: devicetree@...r.kernel.org
> Cc: upstream@...ts.phytec.de
> 
> Signed-off-by: Teresa Remmet <t.remmet@...tec.de>
> ---
> Teresa Remmet (2):
>        dt-bindings: dp83867: add binding for ti,output-impedance property
>        net: phy: dp83867: add numeric io impedance DT property
> 
>   Documentation/devicetree/bindings/net/ti,dp83867.yaml | 19 ++++++++++++++-----
>   drivers/net/phy/dp83867.c                             | 17 +++++++++++++----
>   2 files changed, 27 insertions(+), 9 deletions(-)
> ---
> base-commit: 1f97d9dcf53649c41c33227b345a36902cbb08ad
> change-id: 20260128-wip-t-remmet-phytec-de-bspimx95-132_upstream-48188a567544
> 
> Best regards,