> > What about the other three RGMII modes? Plain rgmii is pretty unusual, > > rgmii-id is the most used. > > > According to the LS1B datasheet, only RGMII and MII are supported. > And I can confirm that MII mode does work for LS1B. What does your device tree look like? What are you setting phy-mode to in the rgmii case? As i said, "rgmii" is pretty unusual, you normally need "rgmii-id". Something in the system needs to add 2ns delays to the RGMII clock lines. Generally in device tree you pass phy-mode = "rgmii-id"; The MAC configures itself for RGMII, and passes PHY_INTERFACE_MODE_RGMII_ID to the PHY when it is attached. The PHY then inserts the delays. What is inserting the delays in your system? Andrew