IMX8M mini RGMII TO RGMII Connection

[HAKANAYDN]

Hello,

I want to connect two IMX8 mini cpu over ethernet RGMII Interface not using external PHY. How can I do ?   Which pin do I connect between IMX8 ? What do I write my linux device tree ?

[JosephAtNXP]

Hi,

Thank you for your interest in NXP Semiconductor products,

Add a fixed-link property, this is the documentation.

This would transform the EVK DTS from:

&fec1 {
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_fec1>;
	phy-mode = "rgmii-id";
	phy-handle = <&ethphy0>;
	fsl,magic-packet;
	status = "okay";

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

		ethphy0: ethernet-phy@0 {
			compatible = "ethernet-phy-ieee802.3-c22";
			reg = <0>;
			reset-gpios = <&gpio4 22 GPIO_ACTIVE_LOW>;
			reset-assert-us = <10000>;
			reset-deassert-us = <80000>;
			realtek,aldps-enable;
			realtek,clkout-disable;
			qca,disable-smarteee;
			vddio-supply = <&vddio>;

			vddio: vddio-regulator {
				regulator-min-microvolt = <1800000>;
				regulator-max-microvolt = <1800000>;
			};
		};
	};
};

To:

&fec1 {
        pinctrl-names = "default";
        pinctrl-0 = <&pinctrl_fec1>;
        phy-mode = "rgmii-id";
	    fsl,magic-packet;
        status = "okay";

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

Pins needed to be mapped are everyone that's under RGMII spec / everyone that would be mapped to a PHY.

Regards

[HAKANAYDN]

Thank you for your quick reply. If I understand correctly, I should connect the below pins each other. is it ? will I do anything about fec clock ?


MX8MM_IOMUXC_ENET_TD3_ENET1_RGMII_TD3 0x1f//
MX8MM_IOMUXC_ENET_TD2_ENET1_RGMII_TD2 0x1f//
MX8MM_IOMUXC_ENET_TD1_ENET1_RGMII_TD1 0x1f//
MX8MM_IOMUXC_ENET_TD0_ENET1_RGMII_TD0 0x1f//

MX8MM_IOMUXC_ENET_RD3_ENET1_RGMII_RD3 0x91//
MX8MM_IOMUXC_ENET_RD2_ENET1_RGMII_RD2 0x91//
MX8MM_IOMUXC_ENET_RD1_ENET1_RGMII_RD1 0x91//
MX8MM_IOMUXC_ENET_RD0_ENET1_RGMII_RD0 0x91//


MX8MM_IOMUXC_ENET_TXC_ENET1_RGMII_TXC 0x1f//
MX8MM_IOMUXC_ENET_RXC_ENET1_RGMII_RXC 0x91//


MX8MM_IOMUXC_ENET_RX_CTL_ENET1_RGMII_RX_CTL 0x91//
MX8MM_IOMUXC_ENET_TX_CTL_ENET1_RGMII_TX_CTL 0x1f//

I did like your dtb file for fec. Then I tried on the board and ping from the board to the other board over RGMII to RGMII  connection but it was not succesfull. I didnt show any TX clock. do I need any external clock source for FEC ? Could you please write step to step what I do for RGMII to RGMII connection ?

[JosephAtNXP]

Hi,

I think I found the issue, according to the bindings definition:

# RX and TX delays are added by the MAC when required
- rgmii

# RGMII with internal RX and TX delays provided by the PHY,
# the MAC should not add the RX or TX delays in this case
- rgmii-id

rgmii should be selected as phy-mode,

TXC is properly configured, let me know if the above change did enable TXC

Thank you,