linux-kernel - Re: [PATCH v3 3/4] net: stmmac: register parent MDIO node for sun8i-h3-emac

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Date:   Wed, 23 Aug 2017 09:49:42 +0200
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Corentin Labbe <clabbe.montjoie@...il.com>,
        Chen-Yu Tsai <wens@...e.org>, Andrew Lunn <andrew@...n.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v3 3/4] net: stmmac: register parent MDIO node for
 sun8i-h3-emac

Hi Florian,

On Tue, Aug 22, 2017 at 11:35:01AM -0700, Florian Fainelli wrote:
> >>> So I think what you are saying is either impossible or engineering-wise
> >>> a very stupid design, like using an external MAC with a discrete PHY
> >>> connected to the internal MAC's MDIO bus, while using the internal MAC
> >>> with the internal PHY.
> >>>
> >>> Now can we please decide on something? We're a week and a half from
> >>> the 4.13 release. If mdio-mux is wrong, then we could have two mdio
> >>> nodes (internal-mdio & external-mdio).
> >>
> >> I really don't see a need for a mdio-mux in the first place, just have
> >> one MDIO controller (current state) sub-node which describes the
> >> built-in STMMAC MDIO controller and declare the internal PHY as a child
> >> node (along with 'phy-is-integrated'). If a different configuration is
> >> used, then just put the external PHY as a child node there.
> >>
> >> If fixed-link is required, the mdio node becomes unused anyway.
> >>
> >> Works for everyone?
> > 
> > If we put an external PHY with reg=1 as a child of internal MDIO,
> > il will be merged with internal PHY node and get
> > phy-is-integrated.
> 
> Then have the .dtsi file contain just the mdio node, but no internal or
> external PHY and push all the internal and external PHY node definition
> (in its entirety) to the per-board DTS file, does not that work?

If possible, I'd really like to have the internal PHY in the
DTSI. It's always there in hardware anyway, and duplicating the PHY,
with its clock, reset line, and whatever info we might need in the
future in each and every board DTS that uses it will be very error
prone and we will have the usual bunch of issues that come up with
duplication.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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