netdev - [RFC] Reset pins of phys and their representation in a device tree

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Message-ID: <20160512071542.GC30822@pengutronix.de>
Date:	Thu, 12 May 2016 09:15:42 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org
Cc:	kernel@...gutronix.de
Subject: [RFC] Reset pins of phys and their representation in a device tree

Hello,

I have a machine here where the reset pin of the phy is connected to a
GPIO.

There are different possibilities available today to handle this
situation, here are the ones I'm aware of:

 - Use a gpio-hog to set the reset gpio to non-active
   This might result in dependency problems (and that's what I am
   currently faced with) because there is no connection in the device
   tree between the hog and the phy.

 - [Documentation/devicetree/bindings/net/fsl-fec.txt]
   The fec node supports properties

	phy-reset-gpios = <&gpio2 14 0>;
	phy-reset-duration = <200> /* milliseconds */;

   Something similar exists in TI's vendor kernel
   (http://git.ti.com/ti-linux-kernel/ti-linux-kernel/commit/17d192b999ee904ced223c16cef76111a51c461b)
   with different (and IMHO bader) naming.
   This is the wrong place to specify the gpios; they shouldn't be in the
   mac's node, but in a phy node instead.

So what I actually want is to put the gpio specification in the right
place and let it look as follows:

	mymdiobus {
		[...]
		myfirstphy: ethernet-phy@0 {
			compatible = "ethernet-phy-ieee802.3-c22";
			reg = <0>;

			reset-gpios = <&gpio2 14 0>;
			reset-duration-ms = <200>;
		};

		mysecondphy: ethernet-phy@2 {
			compatible = "ethernet-phy-ieee802.3-c22";
			reg = <2>;

			reset-gpios = <&gpio3 10 0>;
			reset-duration-ms = <200>;
		};
	};

And with this we could defer probe of &myfirstphy if &gpio2 isn't
available yet.

Does this sound sensible? Does something like that already exist which I
missed? Any further ideas/comments?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |