Re: [PATCH v2 07/10] net: pcs: xpcs: add Rockchip RK3568 platform glue driver

From: Andrew Lunn <andrew@lunn.ch>
To: Coia Prant <coiaprant@gmail.com>
Cc: Andrew Lunn <andrew+netdev@lunn.ch>,
	"David S . Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Heiko Stuebner <heiko@sntech.de>, Vinod Koul <vkoul@kernel.org>,
	Maxime Chevallier <maxime.chevallier@bootlin.com>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>,
	Romain Gantois <romain.gantois@bootlin.com>,
	Heiner Kallweit <hkallweit1@gmail.com>,
	Neil Armstrong <neil.armstrong@linaro.org>,
	Russell King <linux@armlinux.org.uk>,
	Shawn Lin <shawn.lin@rock-chips.com>,
	David Heidelberg <david@ixit.cz>,
	netdev@vger.kernel.org, linux-rockchip@lists.infradead.org,
	devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-phy@lists.infradead.org,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-renesas-soc@vger.kernel.org
Subject: Re: [PATCH v2 07/10] net: pcs: xpcs: add Rockchip RK3568 platform glue driver
Date: Sun, 2 Aug 2026 21:00:38 +0200	[thread overview]
Message-ID: <ba5522ab-1e77-4236-89cd-9483ed1f2da0@lunn.ch> (raw)
In-Reply-To: <58C6FD30-02CF-4DC8-BE7F-4E2AAC5985E4@gmail.com>

> Hi Andrew,
> 
> You're right that the xpcs core uses C45 exclusively, and modern kernels
> no longer require C22 callbacks for mdiobus_register().
> 
> However, I'd prefer to keep them for two reasons:
> 1. Debugging tools (mdio-tools, ethtool, etc.) often use C22 reads to
>    inspect PHY/PCS registers. Having these callbacks makes debugging
>    much easier without having to patch the driver.
> 2. It keeps the driver consistent with pcs-xpcs-plat.c, which also
>    provides both C22 and C45 callbacks even though the xpcs core
>    only uses C45.
> 
> If you strongly prefer removing them to keep the code minimal, I can do
> that in v3. But I think the debug benefit justifies keeping them.

Keep them. I was thinking it side steps the issue of accidentally
mixing up C22 registers and C45 registers. But there are useful use
cases for C22.

      Andrew

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