linux-kernel - Re: [PATCH net-next 0/2] net: phy: dp83822: Add support for changing the transmit amplitude voltage

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Message-ID: <fcffef06-c8d1-4398-bc20-30d252cd2fd2@lunn.ch>
Date: Mon, 13 Jan 2025 14:54:28 +0100
From: Andrew Lunn <andrew@...n.ch>
To: dimitri.fedrau@...bherr.com
Cc: 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 Davis <afd@...com>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Dimitri Fedrau <dima.fedrau@...il.com>
Subject: Re: [PATCH net-next 0/2] net: phy: dp83822: Add support for changing
 the transmit amplitude voltage

On Mon, Jan 13, 2025 at 06:40:11AM +0100, Dimitri Fedrau via B4 Relay wrote:
> Add support for changing the transmit amplitude voltage in 100BASE-TX mode.
> Add support for configuration via DT.

The commit message is supposed to answer the question "Why?". Isn't
reducing the voltage going to make the device non conforming? Why
would i want to break it? I could understand setting it a bit higher
than required to handle losses on the PCB and connector, so the
voltages measured on the RJ45 pins are conforming.

Also, what makes the dp8382 special? I know other PHYs can actually do
this. So why are we adding some vendor specific property just for
100base-tx?

	Andrew