topic Re: RGMII PHY with IM8QM processor (Linux) in i.MX Processors

RGMII PHY with IM8QM processor (Linux)

mahesh_hns — Wed, 19 Mar 2025 18:31:54 GMT

HI,

I have a board with imx8qm processor connected to a Maxlinear PHY. The connection is as follows
IMX8QM <-- RGMII--> MaxLinear PHY <--SGMII-->

What I observe is that the PHY never goes to 1G speed (despite being explicitly set). This setup is functional in 10Mbps. When I measured the clocks TXC and RXC , both were 2.5Mhz , confirming the 10Mbs speed/connection.

Now, I have the below device tree entirees on the IMX8QM linux.

#include <dt-bindings/usb/pd.h>
#include "imx8qp.dtsi"

&fec1 {
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_fec1>;
	phy-mode = "rgmii-txid";
	phy-handle = <&ethphy1>;
	fsl,magic-packet;
	fsl,mii-exclusive;
	nvmem-cells = <&fec_mac0>;
	nvmem-cell-names = "mac-address";
	rx-internal-delay-ps = <2000>;
	status = "okay";

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

		ethphy1: ethernet-phy@1 {  // PHY connected to the MDIO bus
            reg = <1>; // PHY address on the MDIO bus
            compatible = "ethernet-phy-ieee802.3-c22"; // Generic PHY compatible string
            mxl,disable-autoneg = <1>; // Disable Auto negotiation
            mxl,force-speed = <1000>; //  Force speed to 1Gbps
            reset-gpios = <&lsio_gpio3 3 GPIO_ACTIVE_LOW>; // HRST pin connected to GPIO3_IO04
            status = "okay";
        };

	};
};

My configuration requires Auto neg to be disabled and PHY speed set to 1G always.
What might I be doing wrong?

Is there a way I can force the TXC/RXC to 125Mhz?
Or is it that the MAC sets these based on the PHY configuration after reading from the PHY Standard Status registers?
Any thoughts?

Re: RGMII PHY with IM8QM processor (Linux)

JosephAtNXP — Wed, 19 Mar 2025 21:05:39 GMT

Hi,

Thank you for your interest in NXP Semiconductor products,

Please refer to the fec example.

Remove the following properties.

fsl,mii-exclusive; nvmem-cells = <&fec_mac0>; nvmem-cell-names = "mac-address"; ... mxl,disable-autoneg = <1>; // Disable Auto negotiation mxl,force-speed = <1000>; // Force speed to 1Gbps

Used a fixed link property for not negotiating.

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

Regards

Re: RGMII PHY with IM8QM processor (Linux)

mahesh_hns — Fri, 21 Mar 2025 13:20:00 GMT

I thought 'fixed-link' property is only for PHY less connection. I have a Maxlinear PHY connected (which has to load its own software driver to initialize). I am curious how fixed-link wiill help here?