STM32MP157 mdio can not get ethernet phy

the kernel log is : mdio_bus stmmac-0: MDIO device at address 7 is missing.

phy chip is : ksz9031

mpu is : stm32mp157cac3

my dts config is :

&ethernet0 { status = "okay"; pinctrl-0 = <&ethernet0_rgmii_pins_a>; pinctrl-1 = <&ethernet0_rgmii_pins_sleep_a>; pinctrl-names = "default", "sleep"; clock-names = "stmmaceth", "mac-clk-tx", "mac-clk-rx", "ethstp", "eth-ck"; clocks = <&rcc ETHMAC>, <&rcc ETHTX>, <&rcc ETHRX>, <&rcc ETHSTP>, <&rcc ETHCK_K>; assigned-clocks = <&rcc ETHCK_K>; assigned-clock-parents = <&rcc PLL4_P>; assigned-clock-rates = <125000000>; phy-mode = "rgmii"; max-speed = <1000>; phy-handle = <&phy0>; st,eth_clk_sel; mdio0 { #address-cells = <1>; #size-cells = <0>; compatible = "snps,dwmac-mdio"; reset-gpios = <&gpiog 0 GPIO_ACTIVE_LOW>;phy0: ethernet-phy@7 { reg = <7>; /* * These skews assume the STM32MP1 has no internal delay. * * All skews are offset since hardware skew values for the ksz9031 * range from a negative skew to a positive skew. * See the micrel-ksz90x1.txt Documentation file for details. */ /* REG 0x0008, 5 bits per skew */ txc-skew-ps = <1800>;/* 900ps */ rxc-skew-ps = <1320>;/* 420ps */ /* REG 0x0004, 4 bits per skew */ txen-skew-ps = <420>; /* 0ps */ rxdv-skew-ps = <420>; /* 0ps */ /* REG 0x0005, 4 bits per skew */ rxd0-skew-ps = <720>; /* 300ps */ rxd1-skew-ps = <780>; /* 360ps */ rxd2-skew-ps = <840>; /* 420ps */ rxd3-skew-ps = <900>; /* 480ps */ /* REG 0x0006, 4 bits per skew */ txd0-skew-ps = <0>; /* -420ps */ txd1-skew-ps = <60>; /* -360ps */ txd2-skew-ps = <120>; /* -300ps */ txd3-skew-ps = <180>; /* -240ps */ micrel,force-master; }; };};

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the dts config is copied from a runnable dts config which is using a linux4.19 ，but my ver is 5.4

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