linux-kernel - Re: [PATCH net-next 07/15] mfd: core: add ability for cells to probe on a custom parent OF node

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Message-ID: <20260116142204.fjpqvcbc2p72m255@skbuf>
Date: Fri, 16 Jan 2026 16:22:04 +0200
From: Vladimir Oltean <vladimir.oltean@....com>
To: Lee Jones <lee@...nel.org>
Cc: netdev@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
	Heiner Kallweit <hkallweit1@...il.com>,
	Russell King <linux@...linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next 07/15] mfd: core: add ability for cells to probe
 on a custom parent OF node

On Fri, Jan 16, 2026 at 04:02:37PM +0200, Vladimir Oltean wrote:
> On Fri, Jan 16, 2026 at 01:23:45PM +0000, Lee Jones wrote:
> > Please send me the full and finalised DTS hunk.
>
> I gave it to you earlier in this thread, it is (2) from:
> https://lore.kernel.org/netdev/20260109121432.lu2o22iijd4i57qq@skbuf/
> (the actual device tree has more irrelevant properties, the above is
> just the relevant skeleton)
>
> With the mention that in current device trees, the "regs" node and its
> underlying hierachy is missing, and patch 14 from this patch set uses
> the of_changeset API to dynamically fill it in before calling
> mfd_add_devices().

I am a bit torn between not wanting to confuse you by providing
irrelevant information, and not giving the impression that those
properties are all that there is.

The ethernet-switch root node also has all DSA properties that can be
seen in the Documentation/devicetree/bindings/net/dsa/nxp,sja1105.yaml
example. The above properties are all overlaid on top.

Merged together, they would look like this:

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

	sw1: ethernet-switch@0 {
		compatible = "nxp,sja1110a";
		reg = <0>; // means "SPI chip select"

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

			port@0 {
				reg = <0>;
			};

			port@1 {
				reg = <1>;
				pcs-handle = <&sgmii1_pcs>;
			};

			port@2 {
				reg = <2>;
				pcs-handle = <&sgmii2_pcs>;

				fixed-link {
					speed = <1000>;
					full-duplex;
				};
			};

			port@3 {
				reg = <3>;
				pcs-handle = <&sgmii3_pcs>;
			};

			sw1p4: port@4 {
				reg = <4>;
				pcs-handle = <&sgmii4_pcs>;
			};

			port@5 {
				reg = <5>;
				phy-handle = <&sw1_port5_base_t1_phy>;
			};

			port@6 {
				reg = <6>;
				phy-handle = <&sw1_port6_base_t1_phy>;
			};

			port@7 {
				reg = <7>;
				phy-handle = <&sw1_port7_base_t1_phy>;
			};

			port@8 {
				reg = <8>;
				phy-handle = <&sw1_port8_base_t1_phy>;
			};

			port@9 {
				reg = <9>;
				phy-handle = <&sw1_port9_base_t1_phy>;
			};

			port@a {
				reg = <10>;
				phy-handle = <&sw1_port10_base_t1_phy>;
			};
		};

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

			mdio@0 {
				compatible = "nxp,sja1110-base-t1-mdio";
				#address-cells = <1>;
				#size-cells = <0>;
				reg = <0>; // 0 has no physical meaning other than "first bus"

				sw1_port5_base_t1_phy: ethernet-phy@1 {
					compatible = "ethernet-phy-ieee802.3-c45";
					reg = <0x1>;
				};

				sw1_port6_base_t1_phy: ethernet-phy@2 {
					compatible = "ethernet-phy-ieee802.3-c45";
					reg = <0x2>;
				};

				sw1_port7_base_t1_phy: ethernet-phy@3 {
					compatible = "ethernet-phy-ieee802.3-c45";
					reg = <0x3>;
				};

				sw1_port8_base_t1_phy: ethernet-phy@4 {
					compatible = "ethernet-phy-ieee802.3-c45";
					reg = <0x4>;
				};

				sw1_port9_base_t1_phy: ethernet-phy@5 {
					compatible = "ethernet-phy-ieee802.3-c45";
					reg = <0x5>;
				};

				sw1_port10_base_t1_phy: ethernet-phy@6 {
					compatible = "ethernet-phy-ieee802.3-c45";
					reg = <0x6>;
				};
			};

			mdio@1 {
				compatible = "nxp,sja1110-base-tx-mdio";
				#address-cells = <1>;
				#size-cells = <0>;
				reg = <1>; // no physical meaning other than "second bus"

				ethernet-phy@0 {
					reg = <0x0>;
				};
			};
		};

		/* The portion above is established binding. The portion below isn't */

		regs {
			#address-cells = <1>;
			#size-cells = <1>;

			/* The bindings of these PCS devices all come
			 * from Documentation/devicetree/bindings/net/pcs/snps,dw-xpcs.yaml,
			 * they are not defined by me.
			 */
			sgmii1_pcs: ethernet-pcs@...000 { // Physical meaning: untranslatable switch address space
				compatible = "nxp,sja1110-pcs";
				reg = <0x705000 0x1000>;
				reg-names = "indirect";
			};

			sgmii2_pcs: ethernet-pcs@...000 {
				compatible = "nxp,sja1110-pcs";
				reg = <0x706000 0x1000>;
				reg-names = "indirect";
				rx-polarity = <PHY_POL_INVERT>; // THIS LINE is what the entire effort is for.
			};

			sgmii3_pcs: ethernet-pcs@...000 {
				compatible = "nxp,sja1110-pcs";
				reg = <0x707000 0x1000>;
				reg-names = "indirect";
			};

			sgmii4_pcs: ethernet-pcs@...000 {
				compatible = "nxp,sja1110-pcs";
				reg = <0x708000 0x1000>;
				reg-names = "indirect";
			};
		};
	};
};