From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sascha Hauer Subject: Re: [RFC PATCH 1/3] of: provide a binding for the 'fixed-link' property Date: Mon, 12 Aug 2013 10:37:46 +0200 Message-ID: <20130812083746.GM26614@pengutronix.de> References: <1373902450-11857-1-git-send-email-thomas.petazzoni@free-electrons.com> <1373902450-11857-2-git-send-email-thomas.petazzoni@free-electrons.com> <20130812063806.GD2324@pengutronix.de> <20130812101649.743c08aa@skate> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20130812101649.743c08aa@skate> Sender: netdev-owner@vger.kernel.org To: Thomas Petazzoni Cc: Grant Likely , Rob Herring , "David S. Miller" , Florian Fainelli , Lior Amsalem , netdev@vger.kernel.org, devicetree-discuss@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org 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 -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |