PPC440EPx SMII ethernet

We have built a new board based on the PPC440EPx. We are using an SMII-mode phy for the ethernet.

The .dts file started as the one for Sequoia, and I have changed the phy specifier to phy-mode = "smii" - I've also removed the has-mdio property from RGMII0. The ethernet is working in U-Boot, but when Linux tries to start the emac I get:

PPC 4xx OCP EMAC driver, version 3.54
MAL v2 /plb/mcmal, 2 TX channels, 2 RX channels
ZMII /plb/opb/emac-zmii@ef600d00 initialized
RGMII /plb/opb/emac-rgmii@ef601000 initialized without MDIO support /plb/opb/emac-zmii@ef600d00: bridge in SMII mode /plb/opb/emac-rgmii@ef601000: unsupported settings ! /plb/opb/emac-rgmii@ef601000: unsupported settings !

and the ethernet is not functional. I don't see any example .dts files for smii mode. If anyone can tell me what the .dts settings should be for this configuration, I'd appreciate it.

The kernel version is 2.6.28.7 - I know that is a bit old now, but hopefully I can still make progress with it.

Here is the whole .dts section for reference:

	ZMII0: emac-zmii@ef600d00 {
		compatible = "ibm,zmii-440epx", "ibm,zmii";
		reg = <0xef600d00 0x0000000c>;
	};

	RGMII0: emac-rgmii@ef601000 {
		compatible = "ibm,rgmii-440epx", "ibm,rgmii";
		reg = <0xef601000 0x00000008>;
		/* has-mdio; */
	};

	EMAC0: ethernet@ef600e00 {
		device_type = "network";
		compatible = "ibm,emac-440epx", "ibm,emac4";
		interrupt-parent = <&EMAC0>;
		interrupts = <0x0 0x1>;
		#interrupt-cells = <1>;
		#address-cells = <0>;
		#size-cells = <0>;
		interrupt-map = </*Status*/ 0x0 &UIC0 0x18 0x4
				/*Wake*/  0x1 &UIC1 0x1d 0x4>;
		reg = <0xef600e00 0x00000074>;
		local-mac-address = [000000000000];
		mal-device = <&MAL0>;
		mal-tx-channel = <0>;
		mal-rx-channel = <0>;
		cell-index = <0>;
		max-frame-size = <9000>;
		rx-fifo-size = <4096>;
		tx-fifo-size = <2048>;
		phy-mode = "smii";
		phy-map = <0x00000000>;
		zmii-device = <&ZMII0>;
		zmii-channel = <0>;
		rgmii-device = <&RGMII0>;
		rgmii-channel = <0>;
		has-inverted-stacr-oc;
		has-new-stacr-staopc;
	};