Ethernet Link Not Detected When Connecting i.MX8QXP Board Directly to Laptop without router/switch

[adnan_dst]

Hi,

We are using an i.MX8QXP SoM and have built the OS image with the following configuration:

• MACHINE = imx8qxpc0mek

• DISTRO = fsl-imx-wayland

• DISTRO_VERSION = 6.6-scarthgap

• Kernel Version = 6.6.36

Our setup includes two Ethernet ports, and both function properly when auto-negotiation is enabled via the ethtool command if connected over router or a ethernet switch.

Laptops ethernet port works fine and we are already accesing our other devices like imx6,imx8mp,etc by directly connecting the ethernet cable to laptops ethernet port.

The issue arises when trying to connect the board directly to a laptop using an Ethernet cable:

• No link is detected. The Ethernet LEDs on the laptops ethernet port do not turn on.

• We've tried static IP configuration on both the board and the laptop (same gateway and netmask), but the problem persists.

• However, when the board is connected to a router or switch, the link is established immediately, and we're able to access the board successfully, whether using static IP or DHCP.

Since our device is intended for deployment in environments where adding an external router or switch (and its associated power supply) is not feasible, it's important that we can establish a direct Ethernet connection to a laptop.

We’re looking to understand why the link is not detected when connected directly to a laptop, and how to resolve this.

Below is thee ethtool info when it's connected to Laptop directly.

ethtool eth0
Settings for eth0:
Supported ports: [ TP MII ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half
Supported pause frame use: Symmetric
Supports auto-negotiation: No
Supported FEC modes: Not reported
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half
Advertised pause frame use: Symmetric
Advertised auto-negotiation: No
Advertised FEC modes: Not reported
Speed: Unknown!
Duplex: Unknown! (255)
Auto-negotiation: on
Port: MII
PHYAD: 7
Transceiver: external
Supports Wake-on: g
Wake-on: d
Link detected: no

Regards,
Adnan

[adnan_dst]

Hi @JosephAtNXP,

We are using imx8qxp som with custom board.

We are using TIA/EIA-568B Below is table showing our connection (I assume it's straight through cable).

Board Pheonix connector	Signal Name	On Ethernet Cable
1	B-	GREEN
2	B+	WHITE GREEN
3	A-	ORANGE
4	A+	WHITE ORANGE
5	D-	BROWN
6	D+	WHITE BROWN
7	C-	WHITE BLUE
8	C+	BLUE

I have also attached schematics.

Best Regards,
Adnan

[JosephAtNXP]

Hi @adnan_dst,

Could you look for a crossover cable and see if it helps? I will review the material in the meantime.

Regards,

[adnan_dst]

Hi,

We tried with cross cable connection also but we are only able to connect over router or switch.

Please let me know if you want me to change anything else in device tree configuration.

Regards,
Adnan

[JosephAtNXP]

Hi,

You can try to use the property "rgmii-id" instead of "rgmii", then, move to try not setting the "max-speed" property.

Have you reviewed if any initialization is required?

You have to get to low level debug, probe the signals, transmitted and received in U-boot and Linux as the clock and reset signals, also try to probe the PHY in U-boot with mdio readings.

Regards

[adnan_dst]

Hi,

I verified the configuration using "rgmii-id" without setting the rx-internal-delay-ps property, but the same issue persisted. I will now try removing the max-speed property and check again.

Additionally, I’ll update you on the signal probing results in both U-Boot and the Linux kernel without max-speed and with "rgmii-id" mode.

Regards,

[JosephAtNXP]

Hi,

Thank you for your interest in NXP Semiconductor products,

A couple questions, you are running test on i.MX 8 QXP MEK? Is it reproducible with MEK?

Ethtool doesn't know the speed nor duplex mode, could you share your DTS?

What is the cable type you are using? Is it crossover? Have you tried other cables?

Regards