netdev - Re: [PATCH net-next 11/13] net: dsa: sja1105: register the MDIO buses for 100base-T1 and 100base-TX

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Date:   Tue, 25 May 2021 11:54:30 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Andrew Lunn <andrew@...n.ch>
CC:     Vladimir Oltean <olteanv@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH net-next 11/13] net: dsa: sja1105: register the MDIO buses
 for 100base-T1 and 100base-TX

On Tue, May 25, 2021 at 04:18:24AM +0200, Andrew Lunn wrote:
> On Tue, May 25, 2021 at 02:22:12AM +0300, Vladimir Oltean wrote:
> > From: Vladimir Oltean <vladimir.oltean@....com>
> > 
> > The SJA1110 contains two types of integrated PHYs: one 100base-TX PHY
> > and multiple 100base-T1 PHYs.
> > 
> > The access procedure for the 100base-T1 PHYs is also different than it
> > is for the 100base-TX one. So we register 2 MDIO buses, one for the
> > base-TX and the other for the base-T1. Each bus has an OF node which is
> > a child of the "mdio" subnode of the switch, and they are recognized by
> > compatible string.
> 
> The mv88e6xxx also can have two MDIO busses. It is however an internal
> bus for the internal PHYs and an external bus. The code however
> evolved, since earlier devices only had one MDIO i ended up with a
> binding like this:
> 
>        mdio {
>                 #address-cells = <1>;
>                 #size-cells = <0>;
>                 interrupt-parent = <&gpio0>;
>                 interrupts = <27 IRQ_TYPE_LEVEL_LOW>;
>                 interrupt-controller;
>                 #interrupt-cells = <2>;
> 
>                 switch0: switch@0 {
>                         compatible = "marvell,mv88e6390";
>                         reg = <0>;
>                         reset-gpios = <&gpio5 1 GPIO_ACTIVE_LOW>;
> 
>                         mdio {
>                                 #address-cells = <1>;
>                                 #size-cells = <0>;
>                                 switch1phy0: switch1phy0@0 {
>                                         reg = <0>;
>                                         interrupt-parent = <&switch0>;
>                                         interrupts = <0 IRQ_TYPE_LEVEL_HIGH>;
>                                 };
>                         };
> 
>                         mdio1 {
>                                 compatible = "marvell,mv88e6xxx-mdio-external";
>                                 #address-cells = <1>;
>                                 #size-cells = <0>;
>                                 switch1phy9: switch1phy0@9 {
>                                         reg = <9>;
>                                 };
>                         };
>                 };
>         };
> 
> It however sounds like you have the two busses one level deeper?
> 
> It would be good if you document this as part of the binding.

Yes, it looks like this:

	ethernet-switch@2 {
		compatible = "nxp,sja1110a";

		ethernet-ports {
			...
		};

		mdio {
			#address-cells = <1>;
			#size-cells = <0>;

			mdio@0 {
				reg = <0>;
				compatible = "nxp,sja1110-base-t1-mdio";
				#address-cells = <1>;
				#size-cells = <0>;

				sw2_port5_base_t1_phy: ethernet-phy@1 {
					compatible = "ethernet-phy-ieee802.3-c45";
					reg = <0x1>;
				};

				...
			};

			mdio@1 {
				reg = <1>;
				compatible = "nxp,sja1110-base-tx-mdio";
				#address-cells = <1>;
				#size-cells = <0>;

				sw2_port1_base_tx_phy: ethernet-phy@1 {
					reg = <0x1>;
				};
			};
		};
	};

I will try to document it.