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Micrel KSZ8081RNA not probed on MDIO

Question asked by Florian GERMAIN on May 22, 2019
Latest reply on Jun 3, 2019 by Florian GERMAIN


We have developped a custom board using IMX6SX and based on sabresd board.

This board use a Micrel KSZ8081 PHY connectet on RGMII1 and using ENET1_MDIO and ENET1_MDC.

The PHY is detected in uboot and i load kernel and device tree by tftp.

But when the kernel is started, the PHY is not detected by the kernel, so rootfs boot on NFS crash.


My device tree for fec is :


&fec1 {
  pinctrl-names = "default";
  pinctrl-0 = <&pinctrl_enet1>;
  phy-supply = <&reg_enet_3v3>;
  phy-mode = "rmii";
  phy-handle = <&ethphy1>;
  status = "okay";  
  phy-reset-gpios = <&gpio2 1 GPIO_ACTIVE_LOW>; /* ENET1_CRS */
  pinctrl-assert-gpios = <&gpio4 16 GPIO_ACTIVE_HIGH>;

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

    reset-delay-us = <100>;

    ethphy1: ethernet-phy@0 {
    compatible = "micrel,ksz8081";
    device_type = "ethernet-phy";
    reg = <0>;


I added a trace in the fuction mdiobus_read and check that 32 @ are asked.

At this time nothing happend on the MDIO/MDC and so, bus response is 0xFFFF.


I don't find a solution for several days. Anyone has an idea ?


Best regards,