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

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Date:   Tue, 22 Aug 2017 09:59:58 +0200
From:   Corentin Labbe <clabbe.montjoie@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Chen-Yu Tsai <wens@...e.org>, 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

On Mon, Aug 21, 2017 at 04:23:21PM +0200, Andrew Lunn wrote:
> > 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?
> 

Exactly you can change it on the fly, but you need to reset the MAC for enabling the new configuration.
The stmmac driver does not handle mdio-mux. It is why I have a patch which automaticly select parent MDIO node of the PHY node.

For representation we could keep the current. (With a big comment stating that it is a switch)

We can also add a mdio-switch type node, or add a mdio-switch property to mdio-mux.

Regards