Documentation: ACPI: DSD: Document MDIO PHY
Introduce a mechanism based on generic ACPI _DSD device properties definition [1] to get PHYs registered on a MDIO bus and provide them to be connected to MAC. [1] http://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf Describe properties "phy-handle" and "phy-mode". Signed-off-by: Calvin Johnson <calvin.johnson@oss.nxp.com> Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com> Acked-by: Rafael J. Wysocki <rafael@kernel.org> Acked-by: Grant Likely <grant.likely@arm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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Calvin Johnson
David S. Miller
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.. SPDX-License-Identifier: GPL-2.0
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=========================
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MDIO bus and PHYs in ACPI
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=========================
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The PHYs on an MDIO bus [1] are probed and registered using
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fwnode_mdiobus_register_phy().
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Later, for connecting these PHYs to their respective MACs, the PHYs registered
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on the MDIO bus have to be referenced.
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This document introduces two _DSD properties that are to be used
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for connecting PHYs on the MDIO bus [3] to the MAC layer.
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These properties are defined in accordance with the "Device
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Properties UUID For _DSD" [2] document and the
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daffd814-6eba-4d8c-8a91-bc9bbf4aa301 UUID must be used in the Device
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Data Descriptors containing them.
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phy-handle
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----------
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For each MAC node, a device property "phy-handle" is used to reference
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the PHY that is registered on an MDIO bus. This is mandatory for
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network interfaces that have PHYs connected to MAC via MDIO bus.
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During the MDIO bus driver initialization, PHYs on this bus are probed
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using the _ADR object as shown below and are registered on the MDIO bus.
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::
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Scope(\_SB.MDI0)
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{
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Device(PHY1) {
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Name (_ADR, 0x1)
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} // end of PHY1
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Device(PHY2) {
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Name (_ADR, 0x2)
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} // end of PHY2
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}
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Later, during the MAC driver initialization, the registered PHY devices
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have to be retrieved from the MDIO bus. For this, the MAC driver needs
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references to the previously registered PHYs which are provided
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as device object references (e.g. \_SB.MDI0.PHY1).
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phy-mode
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--------
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The "phy-mode" _DSD property is used to describe the connection to
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the PHY. The valid values for "phy-mode" are defined in [4].
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The following ASL example illustrates the usage of these properties.
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DSDT entry for MDIO node
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------------------------
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The MDIO bus has an SoC component (MDIO controller) and a platform
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component (PHYs on the MDIO bus).
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a) Silicon Component
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This node describes the MDIO controller, MDI0
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---------------------------------------------
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::
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Scope(_SB)
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{
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Device(MDI0) {
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Name(_HID, "NXP0006")
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Name(_CCA, 1)
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Name(_UID, 0)
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Name(_CRS, ResourceTemplate() {
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Memory32Fixed(ReadWrite, MDI0_BASE, MDI_LEN)
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Interrupt(ResourceConsumer, Level, ActiveHigh, Shared)
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{
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MDI0_IT
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}
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}) // end of _CRS for MDI0
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} // end of MDI0
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}
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b) Platform Component
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The PHY1 and PHY2 nodes represent the PHYs connected to MDIO bus MDI0
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---------------------------------------------------------------------
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::
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Scope(\_SB.MDI0)
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{
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Device(PHY1) {
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Name (_ADR, 0x1)
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} // end of PHY1
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Device(PHY2) {
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Name (_ADR, 0x2)
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} // end of PHY2
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}
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DSDT entries representing MAC nodes
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-----------------------------------
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Below are the MAC nodes where PHY nodes are referenced.
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phy-mode and phy-handle are used as explained earlier.
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------------------------------------------------------
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::
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Scope(\_SB.MCE0.PR17)
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{
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Name (_DSD, Package () {
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ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
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Package () {
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Package (2) {"phy-mode", "rgmii-id"},
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Package (2) {"phy-handle", \_SB.MDI0.PHY1}
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}
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})
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}
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Scope(\_SB.MCE0.PR18)
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{
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Name (_DSD, Package () {
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ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
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Package () {
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Package (2) {"phy-mode", "rgmii-id"},
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Package (2) {"phy-handle", \_SB.MDI0.PHY2}}
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}
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})
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}
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References
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==========
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[1] Documentation/networking/phy.rst
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[2] https://www.uefi.org/sites/default/files/resources/_DSD-device-properties-UUID.pdf
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[3] Documentation/firmware-guide/acpi/DSD-properties-rules.rst
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[4] Documentation/devicetree/bindings/net/ethernet-controller.yaml
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