1 .. SPDX-License-Identifier: GPL-2.0
2
3 =========================
4 MDIO bus and PHYs in ACPI
5 =========================
6
7 The PHYs on an MDIO bus [phy] are probed and registered using
8 fwnode_mdiobus_register_phy().
9
10 Later, for connecting these PHYs to their respective MACs, the PHYs registered
11 on the MDIO bus have to be referenced.
12
13 This document introduces two _DSD properties that are to be used
14 for connecting PHYs on the MDIO bus [dsd-properties-rules] to the MAC layer.
15
16 These properties are defined in accordance with the "Device
17 Properties UUID For _DSD" [dsd-guide] document and the
18 daffd814-6eba-4d8c-8a91-bc9bbf4aa301 UUID must be used in the Device
19 Data Descriptors containing them.
20
21 phy-handle
22 ----------
23 For each MAC node, a device property "phy-handle" is used to reference
24 the PHY that is registered on an MDIO bus. This is mandatory for
25 network interfaces that have PHYs connected to MAC via MDIO bus.
26
27 During the MDIO bus driver initialization, PHYs on this bus are probed
28 using the _ADR object as shown below and are registered on the MDIO bus.
29
30 .. code-block:: none
31
32 Scope(\_SB.MDI0)
33 {
34 Device(PHY1) {
35 Name (_ADR, 0x1)
36 } // end of PHY1
37
38 Device(PHY2) {
39 Name (_ADR, 0x2)
40 } // end of PHY2
41 }
42
43 Later, during the MAC driver initialization, the registered PHY devices
44 have to be retrieved from the MDIO bus. For this, the MAC driver needs
45 references to the previously registered PHYs which are provided
46 as device object references (e.g. \_SB.MDI0.PHY1).
47
48 phy-mode
49 --------
50 The "phy-mode" _DSD property is used to describe the connection to
51 the PHY. The valid values for "phy-mode" are defined in [ethernet-controller].
52
53 managed
54 -------
55 Optional property, which specifies the PHY management type.
56 The valid values for "managed" are defined in [ethernet-controller].
57
58 fixed-link
59 ----------
60 The "fixed-link" is described by a data-only subnode of the
61 MAC port, which is linked in the _DSD package via
62 hierarchical data extension (UUID dbb8e3e6-5886-4ba6-8795-1319f52a966b
63 in accordance with [dsd-guide] "_DSD Implementation Guide" document).
64 The subnode should comprise a required property ("speed") and
65 possibly the optional ones - complete list of parameters and
66 their values are specified in [ethernet-controller].
67
68 The following ASL example illustrates the usage of these properties.
69
70 DSDT entry for MDIO node
71 ------------------------
72
73 The MDIO bus has an SoC component (MDIO controller) and a platform
74 component (PHYs on the MDIO bus).
75
76 a) Silicon Component
77 This node describes the MDIO controller, MDI0
78 ---------------------------------------------
79
80 .. code-block:: none
81
82 Scope(_SB)
83 {
84 Device(MDI0) {
85 Name(_HID, "NXP0006")
86 Name(_CCA, 1)
87 Name(_UID, 0)
88 Name(_CRS, ResourceTemplate() {
89 Memory32Fixed(ReadWrite, MDI0_BASE, MDI_LEN)
90 Interrupt(ResourceConsumer, Level, ActiveHigh, Shared)
91 {
92 MDI0_IT
93 }
94 }) // end of _CRS for MDI0
95 } // end of MDI0
96 }
97
98 b) Platform Component
99 The PHY1 and PHY2 nodes represent the PHYs connected to MDIO bus MDI0
100 ---------------------------------------------------------------------
101
102 .. code-block:: none
103
104 Scope(\_SB.MDI0)
105 {
106 Device(PHY1) {
107 Name (_ADR, 0x1)
108 } // end of PHY1
109
110 Device(PHY2) {
111 Name (_ADR, 0x2)
112 } // end of PHY2
113 }
114
115 DSDT entries representing MAC nodes
116 -----------------------------------
117
118 Below are the MAC nodes where PHY nodes are referenced.
119 phy-mode and phy-handle are used as explained earlier.
120 ------------------------------------------------------
121
122 .. code-block:: none
123
124 Scope(\_SB.MCE0.PR17)
125 {
126 Name (_DSD, Package () {
127 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
128 Package () {
129 Package (2) {"phy-mode", "rgmii-id"},
130 Package (2) {"phy-handle", \_SB.MDI0.PHY1}
131 }
132 })
133 }
134
135 Scope(\_SB.MCE0.PR18)
136 {
137 Name (_DSD, Package () {
138 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
139 Package () {
140 Package (2) {"phy-mode", "rgmii-id"},
141 Package (2) {"phy-handle", \_SB.MDI0.PHY2}}
142 }
143 })
144 }
145
146 MAC node example where "managed" property is specified.
147 -------------------------------------------------------
148
149 .. code-block:: none
150
151 Scope(\_SB.PP21.ETH0)
152 {
153 Name (_DSD, Package () {
154 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
155 Package () {
156 Package () {"phy-mode", "sgmii"},
157 Package () {"managed", "in-band-status"}
158 }
159 })
160 }
161
162 MAC node example with a "fixed-link" subnode.
163 ---------------------------------------------
164
165 .. code-block:: none
166
167 Scope(\_SB.PP21.ETH1)
168 {
169 Name (_DSD, Package () {
170 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
171 Package () {
172 Package () {"phy-mode", "sgmii"},
173 },
174 ToUUID("dbb8e3e6-5886-4ba6-8795-1319f52a966b"),
175 Package () {
176 Package () {"fixed-link", "LNK0"}
177 }
178 })
179 Name (LNK0, Package(){ // Data-only subnode of port
180 ToUUID("daffd814-6eba-4d8c-8a91-bc9bbf4aa301"),
181 Package () {
182 Package () {"speed", 1000},
183 Package () {"full-duplex", 1}
184 }
185 })
186 }
187
188 References
189 ==========
190
191 [phy] Documentation/networking/phy.rst
192
193 [dsd-properties-rules]
194 Documentation/firmware-guide/acpi/DSD-properties-rules.rst
195
196 [ethernet-controller]
197 Documentation/devicetree/bindings/net/ethernet-controller.yaml
198
199 [dsd-guide] DSD Guide.
200 https://github.com/UEFI/DSD-Guide/blob/main/dsd-guide.adoc, referenced
201 2021-11-30.
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