Re: [PATCH 1/2] arm64: dts: mediatek: mt7622: set PHY address of MT7531 switch to 0x1f

From: Florian Fainelli <f.fainelli@gmail.com>
To: arinc.unal@arinc9.com, Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	AngeloGioacchino Del Regno
	<angelogioacchino.delregno@collabora.com>
Cc: mithat.guner@xeront.com, erkin.bozoglu@xeront.com,
	devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org
Subject: Re: [PATCH 1/2] arm64: dts: mediatek: mt7622: set PHY address of MT7531 switch to 0x1f
Date: Fri, 15 Mar 2024 10:26:41 -0700	[thread overview]
Message-ID: <94e3d09a-e6a4-4808-bc29-3f494b65e170@gmail.com> (raw)
In-Reply-To: <20240314-for-mediatek-mt7531-phy-address-v1-1-52f58db01acd@arinc9.com>

On 3/14/24 05:20, Arınç ÜNAL via B4 Relay wrote:
> From: Arınç ÜNAL <arinc.unal@arinc9.com>
> 
> The MT7531 switch listens on PHY address 0x1f on an MDIO bus. I've got two
> findings that support this. There's no bootstrapping option to change the
> PHY address of the switch. The Linux driver hardcodes 0x1f as the PHY
> address of the switch. So the reg property on the device tree is currently
> ignored by the Linux driver.
> 
> Therefore, describe the correct PHY address on boards that have this
> switch.

Can we call it a pseudo PHY to use a similar terminology as what is done 
through drivers/net/dsa/{bcm_sf2,b53}*?

This is not a real PHY as in it has no actual transceiver/digital signal 
processing logic, this is a piece of logic that snoops for MDIO 
transactions at that specific address and lets you access the switch's 
internal register as if it was a MDIO device.

LGTM otherwise!
-- 
Florian