netdev - Re: net: phy: question about phy_is

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Date:   Tue, 13 Feb 2018 14:15:45 +0900
From:   Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org
Subject: Re: net: phy: question about phy_is_internal for generic-phy

Hi Andrew,
Thank you for your advice.

On Fri, 9 Feb 2018 15:59:54 +0100 <andrew@...n.ch> wrote:

> > There are some SoCs that have a built-in phy, and sometimes
> > these SoCs can choose to use built-in phy or external phy.
> 
> O.K. This is the same use case we had at the end of last year.
> 
> How are the MDIO busses arranged? Is there an internal MDIO bus and an
> external MDIO bus? How do you change between the internal and the
> external? Or is it one bus, with the two PHYs having different
> addresses?
> 
> For the hardware in question last year, an MDIO MUX was implemented.
> The MAC has a phy-handle pointing to either the internal PHY on the
> internal MDIO bus, or the external PHY on the external MDIO bus. The
> MDIO MUX layer would then set the register to select between the two.
> 
> https://patchwork.kernel.org/patch/10025279/

I've checked our hardware configuration.
There are internal and external MDIO buses, and the register selects
between them. I'll consider to apply MDIO MUX layer to our MAC driver
rather than phy_is_internal of generic-phy.

Thank you,

---
Best Regards,
Kunihiko Hayashi