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

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Message-ID: <20170821142321.GE1703@lunn.ch>
Date:   Mon, 21 Aug 2017 16:23:21 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:     Chen-Yu Tsai <wens@...e.org>,
        Corentin Labbe <clabbe.montjoie@...il.com>,
        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

> All muxes are mostly always represented the same way afaik, or do you
> want to simply introduce a new compatible / property?

+      	  mdio-mux {
+		compatible = "allwinner,sun8i-h3-mdio-switch";
+		mdio-parent-bus = <&mdio_parent>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		internal_mdio: mdio@1 {
			reg = <1>;
-			clocks = <&ccu CLK_BUS_EPHY>;
-			resets = <&ccu RST_BUS_EPHY>;
+			#address-cells = <1>;
+			#size-cells = <0>;
+			int_mii_phy: ethernet-phy@1 {
+				compatible = "ethernet-phy-ieee802.3-c22";
+				reg = <1>;
+				clocks = <&ccu CLK_BUS_EPHY>;
+				resets = <&ccu RST_BUS_EPHY>;
+				phy-is-integrated;
+			};
+		};
+		mdio: mdio@0 {
+			reg = <0>;
+			#address-cells = <1>;
+			#size-cells = <0>;
 		};
 		
Hi Maxim

Anybody who knows the MDIO-mux code/binding, knows that it is a run
time mux. You swap the mux per MDIO transaction. You can access all
the PHY and switches on the mux'ed MDIO bus.

However here, it is effectively a boot-time MUX. You cannot change it
on the fly. What happens when somebody has a phandle to a PHY on the
internal and a phandle to a phy on the external? Does the driver at
least return -EINVAL, or -EBUSY? Is there a representation which
eliminates this possibility?

   Andrew