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From: Piergiorgio Beruto <Pier.Beruto@onsemi.com>
To: Andrew Lunn <andrew@lunn.ch>
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        Arndt Schuebel <Arndt.Schuebel@onsemi.com>
Subject: RE: [PATCH net-next v4 00/12] Add support for OPEN Alliance
 10BASE-T1x MACPHY Serial Interface
Thread-Topic: [PATCH net-next v4 00/12] Add support for OPEN Alliance
 10BASE-T1x MACPHY Serial Interface
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Date: Thu, 30 May 2024 21:37:04 +0000
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> From an architecture perspicuity, PHY vendor specific registers should be=
 in the PHY register address space. MAC vendor specific registers should be=
 in the MAC register address space.
I agree 100%. The registers I'm talking about are not PHY or MAC specific. =
They are related to other functions. For example, configuring pins to outpu=
t a clock, an SFD indication, a LED, or other.
Some devices also can configure events driven by the PTP timer to toggle GP=
IOs, capture the timer on rising/falling edge of a GPIO or similar.

> It seems like the Microchip device has some PHY vendor specific registers=
 in the MAC address space. That is bad.
I was not aware of that. I can tell you this is not my case.

> Both your and Microchip device is a single piece of silicon. But i doubt =
there is anything in the standard which actually requires this. The PHY cou=
ld be discrete, on the end of an MDIO bus and an MII bus. That is the typic=
al design for the last 30 years, and what linux is built around. The MAC sh=
ould not assume anything about the PHY, the PHY should not assume anything =
about the MAC, because they are interchangeable.
Yes, to me the MAC and PHY must be separate entities even for the OPEN Alli=
ance TC14/6 protocol. Besides, you can stuff whatever PHY within your MACPH=
Y chip (e.g. 10BASE-T1L).
In "my" driver you need to specify in the DTS the kind of net device and th=
e PHY as a handle.

> The framework does allow you to poke any register anywhere. But i would s=
trongly avoid breaking the layering, it is going to cause you long term mai=
ntenance problems, and is ugly.
On that we agree. Maybe I was just misunderstanding the earlier conversatio=
n where I thought you would not allow specific drivers to access MMS other =
than 0,1,4 and the ones that map to MMDs.
If this is not the case, then I think I'm good.

Thanks!
--Pier