linux-kernel - Re: [net-next RFC PATCH 2/2] net: mdio: Add MDIO bus controller for Airoha AN7583

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Message-ID: <922a7c99-8acf-4b88-8e1a-b7c952e50811@lunn.ch>
Date: Wed, 28 May 2025 01:18:29 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Christian Marangi <ansuelsmth@...il.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	Philipp Zabel <p.zabel@...gutronix.de>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [net-next RFC PATCH 2/2] net: mdio: Add MDIO bus controller for
 Airoha AN7583

On Wed, May 28, 2025 at 12:39:45AM +0200, Christian Marangi wrote:
> On Wed, May 28, 2025 at 12:36:46AM +0200, Andrew Lunn wrote:
> > > +#define AN7583_MDIO_PHY				0xd4
> > > +#define   AN7583_MDIO1_SPEED_MODE		BIT(11)
> > > +#define   AN7583_MDIO0_SPEED_MODE		BIT(10)
> > 
> > Is there any documentation about what these bits do? The bus should
> > default to 2.5Mhz.
> >
> 
> No but I can ask. In theory tho these MDIO controller are used for 10g
> or 2.5g PHY that all require a firmware to load so 2.5MHz makes the boot
> time of 2+ minute.
> 
> The documentation say...
> 
> 1: fast mode
> 0: normal mode
> 
> Very useful I guess :D

Can you put an oscilloscope on the clock line and measure it?

We have the DT property:

  clock-frequency:
    description:
      Desired MDIO bus clock frequency in Hz. Values greater than IEEE 802.3
      defined 2.5MHz should only be used when all devices on the bus support
      the given clock speed.

It would be good to default to normal mode, but allow fast to be
selected, once we know what it actually is.

	Andrew