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

[Arınç ÜNAL]

On 15.03.2024 20:26, Florian Fainelli wrote:
> On 3/14/24 05:20, Arınç ÜNAL via B4 Relay wrote:
> > From: Arınç ÜNAL <arinc.unal@xxxxxxxxxx>
> >
> > 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.

I can get behind calling the switch a psuedo-PHY in the context of MDIO.
However, as described on "22.2.4.5.5 PHYAD (PHY Address)" of "22.2.4.5
Management frame structure" of the active standard IEEE Std 802.3™‐2022,
the field is called "PHY Address". The patch log doesn't give an identifier
as to what a switch is in the context of MDIO. Only that it listens on a
certain PHY address which the term complies with IEEE Std 802.3™‐2022.

So I don't see an improvement to be made on the patch log. Feel free to
elaborate further.

Arınç