1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 PSE Power Interface (PSE PI) Documentation 3 PSE Power Interface (PSE PI) Documentation
4 ========================================== 4 ==========================================
5 5
6 The Power Sourcing Equipment Power Interface ( 6 The Power Sourcing Equipment Power Interface (PSE PI) plays a pivotal role in
7 the architecture of Power over Ethernet (PoE) 7 the architecture of Power over Ethernet (PoE) systems. It is essentially a
8 blueprint that outlines how one or multiple po 8 blueprint that outlines how one or multiple power sources are connected to the
9 eight-pin modular jack, commonly known as the 9 eight-pin modular jack, commonly known as the Ethernet RJ45 port. This
10 connection scheme is crucial for enabling the 10 connection scheme is crucial for enabling the delivery of power alongside data
11 over Ethernet cables. 11 over Ethernet cables.
12 12
13 Documentation and Standards 13 Documentation and Standards
14 --------------------------- 14 ---------------------------
15 15
16 The IEEE 802.3 standard provides detailed docu 16 The IEEE 802.3 standard provides detailed documentation on the PSE PI.
17 Specifically: 17 Specifically:
18 18
19 - Section "33.2.3 PI pin assignments" covers t 19 - Section "33.2.3 PI pin assignments" covers the pin assignments for PoE
20 systems that utilize two pairs for power del 20 systems that utilize two pairs for power delivery.
21 - Section "145.2.4 PSE PI" addresses the confi 21 - Section "145.2.4 PSE PI" addresses the configuration for PoE systems that
22 deliver power over all four pairs of an Ethe 22 deliver power over all four pairs of an Ethernet cable.
23 23
24 PSE PI and Single Pair Ethernet 24 PSE PI and Single Pair Ethernet
25 ------------------------------- 25 -------------------------------
26 26
27 Single Pair Ethernet (SPE) represents a differ 27 Single Pair Ethernet (SPE) represents a different approach to Ethernet
28 connectivity, utilizing just one pair of condu 28 connectivity, utilizing just one pair of conductors for both data and power
29 transmission. Unlike the configurations detail 29 transmission. Unlike the configurations detailed in the PSE PI for standard
30 Ethernet, which can involve multiple power sou 30 Ethernet, which can involve multiple power sourcing arrangements across four or
31 two pairs of wires, SPE operates on a simpler 31 two pairs of wires, SPE operates on a simpler model due to its single-pair
32 design. As a result, the complexities of choos 32 design. As a result, the complexities of choosing between alternative pin
33 assignments for power delivery, as described i 33 assignments for power delivery, as described in the PSE PI for multi-pair
34 Ethernet, are not applicable to SPE. 34 Ethernet, are not applicable to SPE.
35 35
36 Understanding PSE PI 36 Understanding PSE PI
37 -------------------- 37 --------------------
38 38
39 The Power Sourcing Equipment Power Interface ( 39 The Power Sourcing Equipment Power Interface (PSE PI) is a framework defining
40 how Power Sourcing Equipment (PSE) delivers po 40 how Power Sourcing Equipment (PSE) delivers power to Powered Devices (PDs) over
41 Ethernet cables. It details two main configura 41 Ethernet cables. It details two main configurations for power delivery, known
42 as Alternative A and Alternative B, which are 42 as Alternative A and Alternative B, which are distinguished not only by their
43 method of power transmission but also by the i 43 method of power transmission but also by the implications for polarity and data
44 transmission direction. 44 transmission direction.
45 45
46 Alternative A and B Overview 46 Alternative A and B Overview
47 ---------------------------- 47 ----------------------------
48 48
49 - **Alternative A:** Utilizes RJ45 conductors 49 - **Alternative A:** Utilizes RJ45 conductors 1, 2, 3 and 6. In either case of
50 networks 10/100BaseT or 1G/2G/5G/10GBaseT, t 50 networks 10/100BaseT or 1G/2G/5G/10GBaseT, the pairs used are carrying data.
51 The power delivery's polarity in this altern 51 The power delivery's polarity in this alternative can vary based on the MDI
52 (Medium Dependent Interface) or MDI-X (Mediu 52 (Medium Dependent Interface) or MDI-X (Medium Dependent Interface Crossover)
53 configuration. 53 configuration.
54 54
55 - **Alternative B:** Utilizes RJ45 conductors 55 - **Alternative B:** Utilizes RJ45 conductors 4, 5, 7 and 8. In case of
56 10/100BaseT network the pairs used are spare 56 10/100BaseT network the pairs used are spare pairs without data and are less
57 influenced by data transmission direction. T 57 influenced by data transmission direction. This is not the case for
58 1G/2G/5G/10GBaseT network. Alternative B inc 58 1G/2G/5G/10GBaseT network. Alternative B includes two configurations with
59 different polarities, known as variant X and 59 different polarities, known as variant X and variant S, to accommodate
60 different network requirements and device sp 60 different network requirements and device specifications.
61 61
62 Table 145-3 PSE Pinout Alternatives 62 Table 145-3 PSE Pinout Alternatives
63 ----------------------------------- 63 -----------------------------------
64 64
65 The following table outlines the pin configura 65 The following table outlines the pin configurations for both Alternative A and
66 Alternative B. 66 Alternative B.
67 67
68 +------------+-------------------+------------ 68 +------------+-------------------+-----------------+-----------------+-----------------+
69 | Conductor | Alternative A | Alternative 69 | Conductor | Alternative A | Alternative A | Alternative B | Alternative B |
70 | | (MDI-X) | (MDI) 70 | | (MDI-X) | (MDI) | (X) | (S) |
71 +============+===================+============ 71 +============+===================+=================+=================+=================+
72 | 1 | Negative V | Positive V 72 | 1 | Negative V | Positive V | - | - |
73 +------------+-------------------+------------ 73 +------------+-------------------+-----------------+-----------------+-----------------+
74 | 2 | Negative V | Positive V 74 | 2 | Negative V | Positive V | - | - |
75 +------------+-------------------+------------ 75 +------------+-------------------+-----------------+-----------------+-----------------+
76 | 3 | Positive V | Negative V 76 | 3 | Positive V | Negative V | - | - |
77 +------------+-------------------+------------ 77 +------------+-------------------+-----------------+-----------------+-----------------+
78 | 4 | - | - 78 | 4 | - | - | Negative V | Positive V |
79 +------------+-------------------+------------ 79 +------------+-------------------+-----------------+-----------------+-----------------+
80 | 5 | - | - 80 | 5 | - | - | Negative V | Positive V |
81 +------------+-------------------+------------ 81 +------------+-------------------+-----------------+-----------------+-----------------+
82 | 6 | Positive V | Negative V 82 | 6 | Positive V | Negative V | - | - |
83 +------------+-------------------+------------ 83 +------------+-------------------+-----------------+-----------------+-----------------+
84 | 7 | - | - 84 | 7 | - | - | Positive V | Negative V |
85 +------------+-------------------+------------ 85 +------------+-------------------+-----------------+-----------------+-----------------+
86 | 8 | - | - 86 | 8 | - | - | Positive V | Negative V |
87 +------------+-------------------+------------ 87 +------------+-------------------+-----------------+-----------------+-----------------+
88 88
89 .. note:: 89 .. note::
90 - "Positive V" and "Negative V" indicate t 90 - "Positive V" and "Negative V" indicate the voltage polarity for each pin.
91 - "-" indicates that the pin is not used f 91 - "-" indicates that the pin is not used for power delivery in that
92 specific configuration. 92 specific configuration.
93 93
94 PSE PI compatibilities 94 PSE PI compatibilities
95 ---------------------- 95 ----------------------
96 96
97 The following table outlines the compatibility 97 The following table outlines the compatibility between the pinout alternative
98 and the 1000/2.5G/5G/10GBaseT in the PSE 2 pai 98 and the 1000/2.5G/5G/10GBaseT in the PSE 2 pairs connection.
99 99
100 +---------+---------------+------------------- 100 +---------+---------------+---------------------+-----------------------+
101 | Variant | Alternative | Power Feeding Type 101 | Variant | Alternative | Power Feeding Type | Compatibility with |
102 | | (A/B) | (Direct/Phantom) 102 | | (A/B) | (Direct/Phantom) | 1000/2.5G/5G/10GBaseT |
103 +=========+===============+=================== 103 +=========+===============+=====================+=======================+
104 | 1 | A | Phantom 104 | 1 | A | Phantom | Yes |
105 +---------+---------------+------------------- 105 +---------+---------------+---------------------+-----------------------+
106 | 2 | B | Phantom 106 | 2 | B | Phantom | Yes |
107 +---------+---------------+------------------- 107 +---------+---------------+---------------------+-----------------------+
108 | 3 | B | Direct 108 | 3 | B | Direct | No |
109 +---------+---------------+------------------- 109 +---------+---------------+---------------------+-----------------------+
110 110
111 .. note:: 111 .. note::
112 - "Direct" indicate a variant where the po 112 - "Direct" indicate a variant where the power is injected directly to pairs
113 without using magnetics in case of spar 113 without using magnetics in case of spare pairs.
114 - "Phantom" indicate power path over coils 114 - "Phantom" indicate power path over coils/magnetics as it is done for
115 Alternative A variant. 115 Alternative A variant.
116 116
117 In case of PSE 4 pairs, a PSE supporting only 117 In case of PSE 4 pairs, a PSE supporting only 10/100BaseT (which mean Direct
118 Power on pinout Alternative B) is not compatib 118 Power on pinout Alternative B) is not compatible with a 4 pairs
119 1000/2.5G/5G/10GBaseT. 119 1000/2.5G/5G/10GBaseT.
120 120
121 PSE Power Interface (PSE PI) Connection Diagra 121 PSE Power Interface (PSE PI) Connection Diagram
122 ---------------------------------------------- 122 -----------------------------------------------
123 123
124 The diagram below illustrates the connection a 124 The diagram below illustrates the connection architecture between the RJ45
125 port, the Ethernet PHY (Physical Layer), and t 125 port, the Ethernet PHY (Physical Layer), and the PSE PI (Power Sourcing
126 Equipment Power Interface), demonstrating how 126 Equipment Power Interface), demonstrating how power and data are delivered
127 simultaneously through an Ethernet cable. The 127 simultaneously through an Ethernet cable. The RJ45 port serves as the physical
128 interface for these connections, with each of 128 interface for these connections, with each of its eight pins connected to both
129 the Ethernet PHY for data transmission and the 129 the Ethernet PHY for data transmission and the PSE PI for power delivery.
130 130
131 .. code-block:: 131 .. code-block::
132 132
133 +--------------------------+ 133 +--------------------------+
134 | | 134 | |
135 | RJ45 Port | 135 | RJ45 Port |
136 | | 136 | |
137 +--+--+--+--+--+--+--+--+--+ 137 +--+--+--+--+--+--+--+--+--+ +-------------+
138 1| 2| 3| 4| 5| 6| 7| 8| 138 1| 2| 3| 4| 5| 6| 7| 8| | |
139 | | | | | | | o----------------- 139 | | | | | | | o-------------------+ |
140 | | | | | | o--|----------------- 140 | | | | | | o--|-------------------+ +<--- PSE 1
141 | | | | | o--|--|----------------- 141 | | | | | o--|--|-------------------+ |
142 | | | | o--|--|--|----------------- 142 | | | | o--|--|--|-------------------+ |
143 | | | o--|--|--|--|----------------- 143 | | | o--|--|--|--|-------------------+ PSE PI |
144 | | o--|--|--|--|--|----------------- 144 | | o--|--|--|--|--|-------------------+ |
145 | o--|--|--|--|--|--|----------------- 145 | o--|--|--|--|--|--|-------------------+ +<--- PSE 2 (optional)
146 o--|--|--|--|--|--|--|----------------- 146 o--|--|--|--|--|--|--|-------------------+ |
147 | | | | | | | | 147 | | | | | | | | | |
148 +--+--+--+--+--+--+--+--+--+ 148 +--+--+--+--+--+--+--+--+--+ +-------------+
149 | | 149 | |
150 | Ethernet PHY | 150 | Ethernet PHY |
151 | | 151 | |
152 +--------------------------+ 152 +--------------------------+
153 153
154 Simple PSE PI Configuration for Alternative A 154 Simple PSE PI Configuration for Alternative A
155 --------------------------------------------- 155 ---------------------------------------------
156 156
157 The diagram below illustrates a straightforwar 157 The diagram below illustrates a straightforward PSE PI (Power Sourcing
158 Equipment Power Interface) configuration desig 158 Equipment Power Interface) configuration designed to support the Alternative A
159 setup for Power over Ethernet (PoE). This impl 159 setup for Power over Ethernet (PoE). This implementation is tailored to provide
160 power delivery through the data-carrying pairs 160 power delivery through the data-carrying pairs of an Ethernet cable, suitable
161 for either MDI or MDI-X configurations, albeit 161 for either MDI or MDI-X configurations, albeit supporting one variation at a
162 time. 162 time.
163 163
164 .. code-block:: 164 .. code-block::
165 165
166 +-------------+ 166 +-------------+
167 | PSE PI | 167 | PSE PI |
168 8 -----+ +------ 168 8 -----+ +-------------+
169 7 -----+ Rail 1 | 169 7 -----+ Rail 1 |
170 6 -----+------+----------------------+ 170 6 -----+------+----------------------+
171 5 -----+ | | 171 5 -----+ | |
172 4 -----+ | Rail 2 | PSE 172 4 -----+ | Rail 2 | PSE 1
173 3 -----+------/ +------------+ 173 3 -----+------/ +------------+
174 2 -----+--+-------------/ | 174 2 -----+--+-------------/ |
175 1 -----+--/ +------ 175 1 -----+--/ +-------------+
176 | 176 |
177 +-------------+ 177 +-------------+
178 178
179 In this configuration: 179 In this configuration:
180 180
181 - Pins 1 and 2, as well as pins 3 and 6, are u 181 - Pins 1 and 2, as well as pins 3 and 6, are utilized for power delivery in
182 addition to data transmission. This aligns w 182 addition to data transmission. This aligns with the standard wiring for
183 10/100BaseT Ethernet networks where these pa 183 10/100BaseT Ethernet networks where these pairs are used for data.
184 - Rail 1 and Rail 2 represent the positive and 184 - Rail 1 and Rail 2 represent the positive and negative voltage rails, with
185 Rail 1 connected to pins 1 and 2, and Rail 2 185 Rail 1 connected to pins 1 and 2, and Rail 2 connected to pins 3 and 6.
186 More advanced PSE PI configurations may incl 186 More advanced PSE PI configurations may include integrated or external
187 switches to change the polarity of the volta 187 switches to change the polarity of the voltage rails, allowing for
188 compatibility with both MDI and MDI-X config 188 compatibility with both MDI and MDI-X configurations.
189 189
190 More complex PSE PI configurations may include 190 More complex PSE PI configurations may include additional components, to support
191 Alternative B, or to provide additional featur 191 Alternative B, or to provide additional features such as power management, or
192 additional power delivery capabilities such as 192 additional power delivery capabilities such as 2-pair or 4-pair power delivery.
193 193
194 .. code-block:: 194 .. code-block::
195 195
196 +-------------+ 196 +-------------+
197 | PSE PI | 197 | PSE PI |
198 | +---+ 198 | +---+
199 8 -----+--------+ | +----- 199 8 -----+--------+ | +-------------+
200 7 -----+--------+ | Rail 1 | 200 7 -----+--------+ | Rail 1 |
201 6 -----+--------+ +-----------------+ 201 6 -----+--------+ +-----------------+
202 5 -----+--------+ | | 202 5 -----+--------+ | |
203 4 -----+--------+ | Rail 2 | PSE 203 4 -----+--------+ | Rail 2 | PSE 1
204 3 -----+--------+ +----------------+ 204 3 -----+--------+ +----------------+
205 2 -----+--------+ | | 205 2 -----+--------+ | |
206 1 -----+--------+ | +----- 206 1 -----+--------+ | +-------------+
207 | +---+ 207 | +---+
208 +-------------+ 208 +-------------+
209 209
210 Device Tree Configuration: Describing PSE PI C 210 Device Tree Configuration: Describing PSE PI Configurations
211 ---------------------------------------------- 211 -----------------------------------------------------------
212 212
213 The necessity for a separate PSE PI node in th 213 The necessity for a separate PSE PI node in the device tree is influenced by
214 the intricacy of the Power over Ethernet (PoE) 214 the intricacy of the Power over Ethernet (PoE) system's setup. Here are
215 descriptions of both simple and complex PSE PI 215 descriptions of both simple and complex PSE PI configurations to illustrate
216 this decision-making process: 216 this decision-making process:
217 217
218 **Simple PSE PI Configuration:** 218 **Simple PSE PI Configuration:**
219 In a straightforward scenario, the PSE PI setu 219 In a straightforward scenario, the PSE PI setup involves a direct, one-to-one
220 connection between a single PSE controller and 220 connection between a single PSE controller and an Ethernet port. This setup
221 typically supports basic PoE functionality wit 221 typically supports basic PoE functionality without the need for dynamic
222 configuration or management of multiple power 222 configuration or management of multiple power delivery modes. For such simple
223 configurations, detailing the PSE PI within th 223 configurations, detailing the PSE PI within the existing PSE controller's node
224 may suffice, as the system does not encompass 224 may suffice, as the system does not encompass additional complexity that
225 warrants a separate node. The primary focus he 225 warrants a separate node. The primary focus here is on the clear and direct
226 association of power delivery to a specific Et 226 association of power delivery to a specific Ethernet port.
227 227
228 **Complex PSE PI Configuration:** 228 **Complex PSE PI Configuration:**
229 Contrastingly, a complex PSE PI setup may enco 229 Contrastingly, a complex PSE PI setup may encompass multiple PSE controllers or
230 auxiliary circuits that collectively manage po 230 auxiliary circuits that collectively manage power delivery to one Ethernet
231 port. Such configurations might support a rang 231 port. Such configurations might support a range of PoE standards and require
232 the capability to dynamically configure power 232 the capability to dynamically configure power delivery based on the operational
233 mode (e.g., PoE2 versus PoE4) or specific requ 233 mode (e.g., PoE2 versus PoE4) or specific requirements of connected devices. In
234 these instances, a dedicated PSE PI node becom 234 these instances, a dedicated PSE PI node becomes essential for accurately
235 documenting the system architecture. This node 235 documenting the system architecture. This node would serve to detail the
236 interactions between different PSE controllers 236 interactions between different PSE controllers, the support for various PoE
237 modes, and any additional logic required to co 237 modes, and any additional logic required to coordinate power delivery across
238 the network infrastructure. 238 the network infrastructure.
239 239
240 **Guidance:** 240 **Guidance:**
241 241
242 For simple PSE setups, including PSE PI inform 242 For simple PSE setups, including PSE PI information in the PSE controller node
243 might suffice due to the straightforward natur 243 might suffice due to the straightforward nature of these systems. However,
244 complex configurations, involving multiple com 244 complex configurations, involving multiple components or advanced PoE features,
245 benefit from a dedicated PSE PI node. This met 245 benefit from a dedicated PSE PI node. This method adheres to IEEE 802.3
246 specifications, improving documentation clarit 246 specifications, improving documentation clarity and ensuring accurate
247 representation of the PoE system's complexity. 247 representation of the PoE system's complexity.
248 248
249 PSE PI Node: Essential Information 249 PSE PI Node: Essential Information
250 ---------------------------------- 250 ----------------------------------
251 251
252 The PSE PI (Power Sourcing Equipment Power Int 252 The PSE PI (Power Sourcing Equipment Power Interface) node in a device tree can
253 include several key pieces of information crit 253 include several key pieces of information critical for defining the power
254 delivery capabilities and configurations of a 254 delivery capabilities and configurations of a PoE (Power over Ethernet) system.
255 Below is a list of such information, along wit 255 Below is a list of such information, along with explanations for their
256 necessity and reasons why they might not be fo 256 necessity and reasons why they might not be found within a PSE controller node:
257 257
258 1. **Powered Pairs Configuration** 258 1. **Powered Pairs Configuration**
259 259
260 - *Description:* Identifies the pairs used 260 - *Description:* Identifies the pairs used for power delivery in the
261 Ethernet cable. 261 Ethernet cable.
262 - *Necessity:* Essential to ensure the corr 262 - *Necessity:* Essential to ensure the correct pairs are powered according
263 to the board's design. 263 to the board's design.
264 - *PSE Controller Node:* Typically lacks de 264 - *PSE Controller Node:* Typically lacks details on physical pair usage,
265 focusing on power regulation. 265 focusing on power regulation.
266 266
267 2. **Polarity of Powered Pairs** 267 2. **Polarity of Powered Pairs**
268 268
269 - *Description:* Specifies the polarity (po 269 - *Description:* Specifies the polarity (positive or negative) for each
270 powered pair. 270 powered pair.
271 - *Necessity:* Critical for safe and effect 271 - *Necessity:* Critical for safe and effective power transmission to PDs.
272 - *PSE Controller Node:* Polarity managemen 272 - *PSE Controller Node:* Polarity management may exceed the standard
273 functionalities of PSE controllers. 273 functionalities of PSE controllers.
274 274
275 3. **PSE Cells Association** 275 3. **PSE Cells Association**
276 276
277 - *Description:* Details the association of 277 - *Description:* Details the association of PSE cells with Ethernet ports or
278 pairs in multi-cell configurations. 278 pairs in multi-cell configurations.
279 - *Necessity:* Allows for optimized power r 279 - *Necessity:* Allows for optimized power resource allocation in complex
280 systems. 280 systems.
281 - *PSE Controller Node:* Controllers may no 281 - *PSE Controller Node:* Controllers may not manage cell associations
282 directly, focusing instead on power flow 282 directly, focusing instead on power flow regulation.
283 283
284 4. **Support for PoE Standards** 284 4. **Support for PoE Standards**
285 285
286 - *Description:* Lists the PoE standards an 286 - *Description:* Lists the PoE standards and configurations supported by the
287 system. 287 system.
288 - *Necessity:* Ensures system compatibility 288 - *Necessity:* Ensures system compatibility with various PDs and adherence
289 to industry standards. 289 to industry standards.
290 - *PSE Controller Node:* Specific capabilit 290 - *PSE Controller Node:* Specific capabilities may depend on the overall PSE
291 PI design rather than the controller alon 291 PI design rather than the controller alone. Multiple PSE cells per PI
292 do not necessarily imply support for mult 292 do not necessarily imply support for multiple PoE standards.
293 293
294 5. **Protection Mechanisms** 294 5. **Protection Mechanisms**
295 295
296 - *Description:* Outlines additional protec 296 - *Description:* Outlines additional protection mechanisms, such as
297 overcurrent protection and thermal manage 297 overcurrent protection and thermal management.
298 - *Necessity:* Provides extra safety and st 298 - *Necessity:* Provides extra safety and stability, complementing PSE
299 controller protections. 299 controller protections.
300 - *PSE Controller Node:* Some protections m 300 - *PSE Controller Node:* Some protections may be implemented via
301 board-specific hardware or algorithms ext 301 board-specific hardware or algorithms external to the controller.
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