From: Sagar Shrikant Kadam sagar.kadam@sifive.com
[ Upstream commit be969b7cfbcfa8a835a528f1dc467f0975c6d883 ]
HiFive unleashed A00 board has VSC8541-01 ethernet phy, this device is identified as a Revision B device as described in device identification registers. In order to use this phy in the unmanaged mode, it requires a specific reset sequence of logical 0-1-0-1 transition on the NRESET pin as documented here [1].
Currently, the bootloader (fsbl or u-boot-spl) takes care of the phy reset. If due to some reason the phy device hasn't received the reset by the prior stages before the linux macb driver comes into the picture, the MACB mii bus gets probed but the mdio scan fails and is not even able to read the phy ID registers. It gives an error message:
"libphy: MACB_mii_bus: probed mdio_bus 10090000.ethernet-ffffffff: MDIO device at address 0 is missing."
Thus adding the device OUI (Organizationally Unique Identifier) to the phy device node helps to probe the phy device.
[1]: VSC8541-01 datasheet: https://www.mouser.com/ds/2/523/Microsemi_VSC8541-01_Datasheet_10496_V40-114...
Signed-off-by: Sagar Shrikant Kadam sagar.kadam@sifive.com Signed-off-by: Palmer Dabbelt palmerdabbelt@google.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts | 1 + 1 file changed, 1 insertion(+)
diff --git a/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts b/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts index 88cfcb96bf233..cc04e66752aac 100644 --- a/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts +++ b/arch/riscv/boot/dts/sifive/hifive-unleashed-a00.dts @@ -83,6 +83,7 @@ ð0 { phy-mode = "gmii"; phy-handle = <&phy0>; phy0: ethernet-phy@0 { + compatible = "ethernet-phy-id0007.0771"; reg = <0>; }; };