The EN8811H answers its PHY ID from power-on, but a link is only possible once its MD32 MCU runs firmware that the host loads over MDIO into volatile RAM. On systems that keep the firmware files in a filesystem, the files arrive long after the MDIO bus was scanned, and the PHY node alone cannot express that gap. Describe the MCU as an MDIO device of its own, with the PHY node on a child bus underneath it. The device downloads the firmware when the files appear, or adopts firmware the bootloader left running, and registers the child bus only then, so the PHY never becomes visible before the chip can serve it. The reset line belongs to this node, not to the PHY node: firmware lives in volatile RAM, so reset may be asserted only while the MCU is not executing it. On a PHY node the line would be pulsed by every phy_detach() and wipe the running firmware. Assisted-by: LLM Signed-off-by: Aleksei Sviridkin --- .../bindings/net/airoha,en8811h-mcu.yaml | 96 +++++++++++++++++++ 1 file changed, 96 insertions(+) create mode 100644 Documentation/devicetree/bindings/net/airoha,en8811h-mcu.yaml diff --git a/Documentation/devicetree/bindings/net/airoha,en8811h-mcu.yaml b/Documentation/devicetree/bindings/net/airoha,en8811h-mcu.yaml new file mode 100644 index 000000000000..99a494f6ca1e --- /dev/null +++ b/Documentation/devicetree/bindings/net/airoha,en8811h-mcu.yaml @@ -0,0 +1,96 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/net/airoha,en8811h-mcu.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Airoha EN8811H PHY MCU + +maintainers: + - Aleksei Sviridkin + +description: | + The Airoha EN8811H 2.5G PHY is built around an MD32 core that executes + firmware from volatile RAM. The chip answers an MDIO address from + power-on, but the PHY function does not exist until firmware has been + loaded over MDIO, and it disappears again if that RAM is cleared. + + This node describes the MD32 core. The PHY function answers on a child + MDIO bus below it, at the same address the core occupies on the parent + bus, and only while firmware is running. + + The reset line is wired to the core, and asserting it clears the + firmware RAM. It therefore belongs to this node: a reset described on + the PHY node would be pulsed by that node's own lifecycle, whatever + the core is doing. + + A board that has firmware in hand while its MDIO bus is enumerated can + describe the PHY on its own, as airoha,en8811h.yaml does, and that form + stays valid. This binding is for the boards where firmware arrives + later, so that there is no PHY to describe until the core has it. + +properties: + compatible: + const: airoha,en8811h-mcu + + reg: + maxItems: 1 + + reset-gpios: + maxItems: 1 + description: + The GPIO phandle and specifier for the reset signal wired to the + MD32 core. + + reset-assert-us: + description: + Delay after the reset was asserted in microseconds. If this + property is missing the delay will be skipped. + + reset-deassert-us: + description: + Delay after the reset was deasserted in microseconds. If this + property is missing the delay will be skipped. + + mdio: + $ref: mdio.yaml# + unevaluatedProperties: false + description: + The bus the PHY function answers on while firmware is running, at + the same address this node occupies on the parent bus. + +required: + - compatible + - reg + - mdio + +additionalProperties: false + +examples: + - | + #include + #include + + mdio { + #address-cells = <1>; + #size-cells = <0>; + + ethernet-phy-mcu@d { + compatible = "airoha,en8811h-mcu"; + reg = <0xd>; + reset-gpios = <&pio 14 GPIO_ACTIVE_LOW>; + reset-assert-us = <10000>; + reset-deassert-us = <20000>; + + mdio { + #address-cells = <1>; + #size-cells = <0>; + + ethernet-phy@d { + compatible = "ethernet-phy-id03a2.a411"; + reg = <0xd>; + interrupts-extended = <&pio 15 IRQ_TYPE_LEVEL_LOW>; + }; + }; + }; + }; -- 2.53.0