netdev - Re: [PATCH net] net: mdio: Prevent Clause 45 scan on SMSC PHYs

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Message-Id: <720C5B4D-6C26-48AC-97D0-9D3729E72DB3@easyb.ch>
Date: Tue, 2 Jan 2024 21:05:17 +0100
From: Ezra Buehler <ezra@...yb.ch>
To: Andrew Lunn <andrew@...n.ch>
Cc: Heiner Kallweit <hkallweit1@...il.com>,
 Russell King <linux@...linux.org.uk>,
 Tristram Ha <Tristram.Ha@...rochip.com>, Michael Walle <michael@...le.cc>,
 Jesse Brandeburg <jesse.brandeburg@...el.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net] net: mdio: Prevent Clause 45 scan on SMSC PHYs

> On 2 Jan 2024, at 20:49, Andrew Lunn <andrew@...n.ch> wrote:
> 
>> By skimming over some datasheets for similar SMSC/Microchip PHYs, I
>> could not find any evidence that they support Clause 45 scanning
>> (other than not responding).
> 
> Do you find any reference to Clause 22 scanning being supported in the
> datasheets?

E.g. the one for the LAN8720A actually states:

This interface supports registers 0 through 6 as required by Clause 22 of the 802.3 standard, as well as “vendor- specific” registers 16 to 31 allowed by the specification. Non-supported registers (such as 7 to 15) will be read as hexadecimal “FFFF”. 

> I'm with Russell here, we should understand why its so slow. And by
> fixing that, you might find access in general gets better.

I agree. I will dig deeper.

Cheers,
Ezra.