netdev - Re: [PATCH 1/5 v2] mv643xx_eth: add Device Tree bindings

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Date:	Fri, 5 Apr 2013 12:04:43 -0600
From:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Cc:	Florian Fainelli <florian@...nwrt.org>,
	thomas.petazzoni@...e-electrons.com, moinejf@...e.fr,
	Simon Baatz <gmbnomis@...il.com>, andrew@...n.ch,
	netdev@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
	rob.herring@...xeda.com, grant.likely@...retlab.ca,
	jogo@...nwrt.org, linux-arm-kernel@...ts.infradead.org,
	jm@...tin.co.uk, davem@...emloft.net, buytenh@...tstofly.org,
	jason@...edaemon.net
Subject: Re: [PATCH 1/5 v2] mv643xx_eth: add Device Tree bindings

On Fri, Apr 05, 2013 at 03:58:03PM +0200, Sebastian Hesselbarth wrote:

> I don't think that the ethernet controller should probe the PHY's on mdio-bus
> at all. At least not for DT enabled platforms. I had a look at DT and non-DT
> mdio-bus sources, and realized that there is a bus scan for non-DT only.
> of_mdiobus_register requires you to set (and know) the PHY address.

DT platforms should have the option to use the standard phy-phandle
connection:


		mdio@...04 {
			#address-cells = <1>;
			#size-cells = <0>;
			compatible = "marvell,orion-mdio";
			reg = <0x72004 0x84>;
			status = "disabled";

+                        PHY1: ethernet-phy@1 {
+                                reg = <1>;
+                                device_type = "ethernet-phy";
+                        };
		};

		ethernet-group@...00 {
			#address-cells = <1>;
			#size-cells = <0>;
			compatible = "marvell,mv643xx-eth-block";
			reg = <0x72000 0x4000>;
			tx-csum-limit = <1600>;
			status = "disabled";

			egiga0: ethernet@0 {
				device_type = "network";
				compatible = "marvell,mv643xx-eth";
				reg = <0>;
				interrupts = <29>;
				clocks = <&gate_clk 2>;
+	                        phy-handle = <&PHY1>;
			};
		};

When phy-handle is present the ethernet driver should not probe/scan for
phys.

There is standard code to handle all of this - an important gain is
that the phy driver now has access to a DT node and can apply
phy-specific properties.

> We had a similar discussion whether to probe or not for DT nodes,
> and I guess there also will be some discussion about the above
> patch. OTOH we could just (again) ask users of every
> kirkwood/orion5x/dove board to tell their phy addresses and fail to
> probe the phy for new boards...

Maybe print a warning and call the no-DT phy probe code if phy-handle
is nor present?

Not sure this should be in the common code, phy probing is sketchy, it
shouldn't be encouraged, IMHO..

Jason
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