From: Sascha Hauer <s.hauer@pengutronix.de>
To: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Grant Likely <grant.likely@secretlab.ca>,
Rob Herring <rob.herring@calxeda.com>,
"David S. Miller" <davem@davemloft.net>,
Florian Fainelli <florian@openwrt.org>,
Lior Amsalem <alior@marvell.com>,
netdev@vger.kernel.org, devicetree-discuss@lists.ozlabs.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 1/3] of: provide a binding for the 'fixed-link' property
Date: Mon, 12 Aug 2013 10:37:46 +0200 [thread overview]
Message-ID: <20130812083746.GM26614@pengutronix.de> (raw)
In-Reply-To: <20130812101649.743c08aa@skate>
On Mon, Aug 12, 2013 at 10:16:49AM +0200, Thomas Petazzoni wrote:
> Dear Sascha Hauer,
>
> On Mon, 12 Aug 2013 08:38:06 +0200, Sascha Hauer wrote:
>
> > > This patch adds:
> > >
> > > * A documentation for the Device Tree property "fixed-link".
> > >
> > > * A of_phy_register_fixed_link() OF helper, which provided an OF node
> > > that contains a "fixed-link" property, registers the corresponding
> > > fixed PHY.
> > >
> > > * Removes the warning on the of_phy_connect_fixed_link() that says
> > > new drivers should not use it, since Grant Likely indicated that
> > > this "fixed-link" property is indeed the way to go.
> > >
> >
> > Any progress with this series?
>
> I am not sure there really was a consensus yet on what the DT binding
> looks like. As soon as there is a consensus, I'm definitely willing to
> make progress on this series.
>
> > We have more and more boards here with exactly the same problem as
> > Thomas has. For reasons stated below I don't like this binding, but
> > still it would solve my problem.
>
> Ok.
>
> > > +Example:
> > > +
> > > +ethernet@0 {
> > > + ...
> > > + fixed-link = <1 1 1000 0 0>;
> > > + ...
> > > +};
> >
> > I must say I don't like this binding at all for two reasons.
>
> As I explained, this binding was chosen for this RFC for two reasons:
>
> * It's the binding used on PowerPC platforms to represent fixed links.
> * It allows to encode all the informations into a single property,
> which avoids the need for a separate DT node for a "fake PHY", which
> isn't a representation of the hardware.
The fake phy is avoided by making the other side of the link what it
really is: An ethernet switch. I'm currently not aware of a situation
where a fixed link is needed and the other side is not a switch. And I
can't think of a situation in which the other side of the other side of
the fixed link really is pure 'virtual', I mean there always must be
something connected, right?
>
> > First the positional arguments make it impossible to add optional
> > arguments to the link.
> >
> > Second the other side of the link is most likely a switch. Once this
> > switch has its own node in the devicetree it seems like having a phandle
> > to the switch here would be better.
>
> So, in other words, what you're suggesting is something like:
>
> ethernet@0 {
> reg = <...>;
> interrupt = <...>;
> phy = <&phy0>;
> phy0: phy@0 {
> fixed-link;
> speed = <1000>;
> full-duplex;
> ...
> };
> };
Yes, this looks good. ePAPR suggests naming the phy property
"phy-handle" instead of just "phy", but that's just details. In case the
phy really is a switch the phandle could just point to a i2c device instead
of the ethernet node.
Sascha
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next prev parent reply other threads:[~2013-08-12 8:37 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-15 15:34 [RFC PATCH 0/3] Add DT support for fixed PHYs Thomas Petazzoni
2013-07-15 15:34 ` [RFC PATCH 1/3] of: provide a binding for the 'fixed-link' property Thomas Petazzoni
2013-07-15 15:50 ` Florian Fainelli
2013-07-23 11:22 ` Mark Rutland
2013-07-23 11:39 ` Florian Fainelli
2013-07-30 9:16 ` Thomas Petazzoni
2013-07-30 10:26 ` Florian Fainelli
2013-07-30 15:28 ` Mark Rutland
2013-07-23 11:39 ` Grant Likely
2013-07-30 9:07 ` Thomas Petazzoni
2013-07-30 10:05 ` Florian Fainelli
2013-07-30 11:23 ` Thomas Petazzoni
2013-07-30 11:43 ` Florian Fainelli
2013-07-30 15:31 ` Mark Rutland
2013-08-12 6:38 ` Sascha Hauer
2013-08-12 8:16 ` Thomas Petazzoni
2013-08-12 8:37 ` Sascha Hauer [this message]
2013-08-21 10:55 ` Christian Gmeiner
2013-08-21 11:25 ` Florian Fainelli
2013-08-21 11:46 ` Florian Fainelli
2013-07-15 15:34 ` [RFC PATCH 2/3] net: phy: call mdiobus_scan() after adding a fixed PHY Thomas Petazzoni
2013-07-15 15:46 ` Florian Fainelli
2013-07-15 15:34 ` [RFC PATCH 3/3] net: mvneta: add support for fixed links Thomas Petazzoni
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