PSE Power Interface(PSE PI)

PSE PI 역할과 Single Pair Ethernet

PSE Power Interface(PSE PI)는 PoE architecture에서 하나 이상의 power source를 8-pin modular jack인 Ethernet RJ45 port에 어떻게 연결하는지 정의하는 blueprint입니다. 이 배치가 Ethernet cable로 data와 power를 동시에 전달하게 합니다.

IEEE 802.3의 `33.2.3 PI pin assignments`는 두 pair로 power를 공급하는 PoE pin 배치를, `145.2.4 PSE PI`는 네 pair 모두로 power를 공급하는 PoE 구성을 설명합니다.

Single Pair Ethernet(SPE)은 conductor 한 pair만으로 data와 power를 모두 전달합니다. 표준 multi-pair Ethernet의 PSE PI는 두 pair 또는 네 pair에 여러 power source 배치를 선택해야 하지만 SPE는 single-pair 구조라 Alternative pin assignment 선택의 복잡성이 적용되지 않습니다.

.. SPDX-License-Identifier: GPL-2.0

PSE Power Interface (PSE PI) Documentation
==========================================

The Power Sourcing Equipment Power Interface (PSE PI) plays a pivotal role in
the architecture of Power over Ethernet (PoE) systems. It is essentially a
blueprint that outlines how one or multiple power sources are connected to the
eight-pin modular jack, commonly known as the Ethernet RJ45 port. This
connection scheme is crucial for enabling the delivery of power alongside data
over Ethernet cables.

Documentation and Standards
---------------------------

The IEEE 802.3 standard provides detailed documentation on the PSE PI.
Specifically:

- Section "33.2.3 PI pin assignments" covers the pin assignments for PoE
  systems that utilize two pairs for power delivery.
- Section "145.2.4 PSE PI" addresses the configuration for PoE systems that
  deliver power over all four pairs of an Ethernet cable.

PSE PI and Single Pair Ethernet
-------------------------------

Single Pair Ethernet (SPE) represents a different approach to Ethernet
connectivity, utilizing just one pair of conductors for both data and power
transmission. Unlike the configurations detailed in the PSE PI for standard
Ethernet, which can involve multiple power sourcing arrangements across four or
two pairs of wires, SPE operates on a simpler model due to its single-pair
design. As a result, the complexities of choosing between alternative pin
assignments for power delivery, as described in the PSE PI for multi-pair
Ethernet, are not applicable to SPE.

Alternative A와 B

PSE PI는 PSE가 Ethernet cable을 통해 PD에 power를 공급하는 방법을 정의하며 주요 구성은 Alternative A와 Alternative B입니다. 두 방식은 power 전송 pair뿐 아니라 polarity와 data 전송 방향의 영향도 다릅니다.

Alternative A는 RJ45 conductor 1, 2, 3, 6을 사용합니다. 10/100BaseT와 1G/2G/5G/10GBaseT 모두 이 pair가 data도 운반합니다. Power polarity는 MDI 또는 MDI-X 구성에 따라 달라질 수 있습니다.

Alternative B는 conductor 4, 5, 7, 8을 사용합니다. 10/100BaseT에서는 data를 쓰지 않는 spare pair이므로 data 전송 방향의 영향이 적지만, 1G/2G/5G/10GBaseT에서는 그렇지 않습니다. 요구와 device 사양에 맞춰 polarity가 다른 variant X와 S가 있습니다.

Understanding PSE PI
--------------------

The Power Sourcing Equipment Power Interface (PSE PI) is a framework defining
how Power Sourcing Equipment (PSE) delivers power to Powered Devices (PDs) over
Ethernet cables. It details two main configurations for power delivery, known
as Alternative A and Alternative B, which are distinguished not only by their
method of power transmission but also by the implications for polarity and data
transmission direction.

Alternative A and B Overview
----------------------------

- **Alternative A:** Utilizes RJ45 conductors 1, 2, 3 and 6. In either case of
  networks 10/100BaseT or 1G/2G/5G/10GBaseT, the pairs used are carrying data.
  The power delivery's polarity in this alternative can vary based on the MDI
  (Medium Dependent Interface) or MDI-X (Medium Dependent Interface Crossover)
  configuration.

- **Alternative B:** Utilizes RJ45 conductors 4, 5, 7 and 8. In case of
  10/100BaseT network the pairs used are spare pairs without data and are less
  influenced by data transmission direction. This is not the case for
  1G/2G/5G/10GBaseT network. Alternative B includes two configurations with
  different polarities, known as variant X and variant S, to accommodate
  different network requirements and device specifications.

Pin polarity와 고속 Base-T 호환성

Alternative A의 MDI-X에서는 conductor 1·2가 Negative V, 3·6이 Positive V이고 MDI에서는 반대입니다. Alternative B variant X에서는 4·5가 Negative V, 7·8이 Positive V이며 variant S에서는 반대입니다. `-`는 해당 구성에서 그 pin을 power delivery에 쓰지 않는다는 뜻입니다.

2-pair PSE와 1000/2.5G/5G/10GBaseT 호환성은 feeding type에 좌우됩니다. Variant 1 Alternative A의 phantom feeding과 variant 2 Alternative B의 phantom feeding은 호환됩니다. Variant 3 Alternative B direct feeding은 호환되지 않습니다.

`Direct`는 spare pair에 magnetics를 거치지 않고 power를 직접 주입합니다. `Phantom`은 Alternative A처럼 coil·magnetics를 통하는 power path입니다.

4-pair PSE에서 10/100BaseT만 지원하여 Alternative B pinout에 direct power를 사용하는 PSE는 4-pair 1000/2.5G/5G/10GBaseT와 호환되지 않습니다.

Table 145-3 PSE Pinout Alternatives
-----------------------------------

The following table outlines the pin configurations for both Alternative A and
Alternative B.

+------------+-------------------+-----------------+-----------------+-----------------+
| Conductor  | Alternative A     | Alternative A   | Alternative B   | Alternative B   |
|            |    (MDI-X)        |      (MDI)      |        (X)      |        (S)      |
+============+===================+=================+=================+=================+
| 1          | Negative V        | Positive V      | -               | -               |
+------------+-------------------+-----------------+-----------------+-----------------+
| 2          | Negative V        | Positive V      | -               | -               |
+------------+-------------------+-----------------+-----------------+-----------------+
| 3          | Positive V        | Negative V      | -               | -               |
+------------+-------------------+-----------------+-----------------+-----------------+
| 4          | -                 | -               | Negative V      | Positive V      |
+------------+-------------------+-----------------+-----------------+-----------------+
| 5          | -                 | -               | Negative V      | Positive V      |
+------------+-------------------+-----------------+-----------------+-----------------+
| 6          | Positive V        | Negative V      | -               | -               |
+------------+-------------------+-----------------+-----------------+-----------------+
| 7          | -                 | -               | Positive V      | Negative V      |
+------------+-------------------+-----------------+-----------------+-----------------+
| 8          | -                 | -               | Positive V      | Negative V      |
+------------+-------------------+-----------------+-----------------+-----------------+

.. note::
    - "Positive V" and "Negative V" indicate the voltage polarity for each pin.
    - "-" indicates that the pin is not used for power delivery in that
      specific configuration.

PSE PI compatibilities
----------------------

The following table outlines the compatibility between the pinout alternative
and the 1000/2.5G/5G/10GBaseT in the PSE 2 pairs connection.

+---------+---------------+---------------------+-----------------------+
| Variant | Alternative   | Power Feeding Type  | Compatibility with    |
|         | (A/B)         | (Direct/Phantom)    | 1000/2.5G/5G/10GBaseT |
+=========+===============+=====================+=======================+
| 1       | A             | Phantom             | Yes                   |
+---------+---------------+---------------------+-----------------------+
| 2       | B             | Phantom             | Yes                   |
+---------+---------------+---------------------+-----------------------+
| 3       | B             | Direct              | No                    |
+---------+---------------+---------------------+-----------------------+

.. note::
    - "Direct" indicate a variant where the power is injected directly to pairs
       without using magnetics in case of spare pairs.
    - "Phantom" indicate power path over coils/magnetics as it is done for
       Alternative A variant.

In case of PSE 4 pairs, a PSE supporting only 10/100BaseT (which mean Direct
Power on pinout Alternative B) is not compatible with a 4 pairs
1000/2.5G/5G/10GBaseT.

RJ45·PHY·PSE PI 연결 architecture

원문의 첫 diagram은 RJ45 port, Ethernet PHY, PSE PI 사이 연결을 보여 줍니다. RJ45의 8개 pin은 data 전송을 위해 Ethernet PHY에 연결되고 power delivery를 위해 PSE PI에도 연결되어 한 cable에서 두 기능이 동시에 작동합니다.

PSE PI에는 PSE 1이 연결되고 PSE 2는 optional입니다. PSE source 하나 또는 둘을 PI가 RJ45 pair에 배치하며 PHY data path와 병렬로 전력 경로를 형성합니다.

PSE Power Interface (PSE PI) Connection Diagram
-----------------------------------------------

The diagram below illustrates the connection architecture between the RJ45
port, the Ethernet PHY (Physical Layer), and the PSE PI (Power Sourcing
Equipment Power Interface), demonstrating how power and data are delivered
simultaneously through an Ethernet cable. The RJ45 port serves as the physical
interface for these connections, with each of its eight pins connected to both
the Ethernet PHY for data transmission and the PSE PI for power delivery.

.. code-block::

    +--------------------------+
    |                          |
    |          RJ45 Port       |
    |                          |
    +--+--+--+--+--+--+--+--+--+                +-------------+
      1| 2| 3| 4| 5| 6| 7| 8|                   |             |
       |  |  |  |  |  |  |  o-------------------+             |
       |  |  |  |  |  |  o--|-------------------+             +<--- PSE 1
       |  |  |  |  |  o--|--|-------------------+             |
       |  |  |  |  o--|--|--|-------------------+             |
       |  |  |  o--|--|--|--|-------------------+  PSE PI     |
       |  |  o--|--|--|--|--|-------------------+             |
       |  o--|--|--|--|--|--|-------------------+             +<--- PSE 2 (optional)
       o--|--|--|--|--|--|--|-------------------+             |
       |  |  |  |  |  |  |  |                   |             |
    +--+--+--+--+--+--+--+--+--+                +-------------+
    |                          |
    |       Ethernet PHY       |
    |                          |
    +--------------------------+

단순 Alternative A와 복합 PI

단순 PSE PI 예는 Alternative A를 지원하며 data-carrying pair로 power를 공급합니다. MDI 또는 MDI-X 중 한 variation을 한 번에 지원합니다.

Pin 1·2와 pin 3·6은 10/100BaseT data 전송과 power delivery를 함께 담당합니다. Rail 1은 pin 1·2, Rail 2는 pin 3·6에 연결되며 두 rail은 positive와 negative voltage를 나타냅니다.

더 발전된 PI는 integrated 또는 external switch로 rail polarity를 바꾸어 MDI와 MDI-X 모두에 호환될 수 있습니다. Alternative B 지원, power management, 2-pair·4-pair power delivery를 위해 추가 component를 둘 수도 있습니다.

두 번째 diagram의 복합 PI는 8개 pin을 내부 switching·routing logic에 연결하여 Rail 1과 Rail 2에 배치합니다. 단순한 고정 pair 연결보다 다양한 mode와 polarity를 관리할 수 있는 구조입니다.

Simple PSE PI Configuration for Alternative A
---------------------------------------------

The diagram below illustrates a straightforward PSE PI (Power Sourcing
Equipment Power Interface) configuration designed to support the Alternative A
setup for Power over Ethernet (PoE). This implementation is tailored to provide
power delivery through the data-carrying pairs of an Ethernet cable, suitable
for either MDI or MDI-X configurations, albeit supporting one variation at a
time.

.. code-block::

         +-------------+
         |    PSE PI   |
 8  -----+                             +-------------+
 7  -----+                    Rail 1   |
 6  -----+------+----------------------+
 5  -----+      |                      |
 4  -----+      |             Rail 2   |  PSE 1
 3  -----+------/         +------------+
 2  -----+--+-------------/            |
 1  -----+--/                          +-------------+
         |
         +-------------+

In this configuration:

- Pins 1 and 2, as well as pins 3 and 6, are utilized for power delivery in
  addition to data transmission. This aligns with the standard wiring for
  10/100BaseT Ethernet networks where these pairs are used for data.
- Rail 1 and Rail 2 represent the positive and negative voltage rails, with
  Rail 1 connected to pins 1 and 2, and Rail 2 connected to pins 3 and 6.
  More advanced PSE PI configurations may include integrated or external
  switches to change the polarity of the voltage rails, allowing for
  compatibility with both MDI and MDI-X configurations.

More complex PSE PI configurations may include additional components, to support
Alternative B, or to provide additional features such as power management, or
additional power delivery capabilities such as 2-pair or 4-pair power delivery.

.. code-block::

         +-------------+
         |    PSE PI   |
         |        +---+
 8  -----+--------+   |                 +-------------+
 7  -----+--------+   |       Rail 1   |
 6  -----+--------+   +-----------------+
 5  -----+--------+   |                |
 4  -----+--------+   |       Rail 2   |  PSE 1
 3  -----+--------+   +----------------+
 2  -----+--------+   |                |
 1  -----+--------+   |                 +-------------+
         |        +---+
         +-------------+

Device Tree에서 별도 PI node를 둘 기준

Device Tree에 별도 PSE PI node가 필요한지는 PoE system 구성의 복잡성에 따라 결정합니다.

단순 구성은 PSE controller 하나와 Ethernet port 하나가 일대일로 직접 연결되고, dynamic configuration이나 여러 power delivery mode 관리 없이 기본 PoE만 지원합니다. 이 경우 기존 PSE controller node 안에 PI 정보를 포함해도 충분하며 특정 port에 power가 직접 연결된 관계를 표현하면 됩니다.

복합 구성은 여러 PSE controller나 auxiliary circuit가 하나의 Ethernet port에 power를 공급할 수 있습니다. PoE2와 PoE4 같은 여러 mode를 지원하고 동작 mode나 연결 PD 요구에 따라 power delivery를 동적으로 설정해야 할 수 있습니다.

이때는 별도 PSE PI node가 controller 상호작용, 지원 PoE mode, 전력 조정을 위한 추가 logic을 정확히 문서화하는 데 필요합니다. IEEE 802.3에 맞춰 system 복잡성을 명확하게 표현할 수 있습니다.

Device Tree Configuration: Describing PSE PI Configurations
-----------------------------------------------------------

The necessity for a separate PSE PI node in the device tree is influenced by
the intricacy of the Power over Ethernet (PoE) system's setup. Here are
descriptions of both simple and complex PSE PI configurations to illustrate
this decision-making process:

**Simple PSE PI Configuration:**
In a straightforward scenario, the PSE PI setup involves a direct, one-to-one
connection between a single PSE controller and an Ethernet port. This setup
typically supports basic PoE functionality without the need for dynamic
configuration or management of multiple power delivery modes. For such simple
configurations, detailing the PSE PI within the existing PSE controller's node
may suffice, as the system does not encompass additional complexity that
warrants a separate node. The primary focus here is on the clear and direct
association of power delivery to a specific Ethernet port.

**Complex PSE PI Configuration:**
Contrastingly, a complex PSE PI setup may encompass multiple PSE controllers or
auxiliary circuits that collectively manage power delivery to one Ethernet
port. Such configurations might support a range of PoE standards and require
the capability to dynamically configure power delivery based on the operational
mode (e.g., PoE2 versus PoE4) or specific requirements of connected devices. In
these instances, a dedicated PSE PI node becomes essential for accurately
documenting the system architecture. This node would serve to detail the
interactions between different PSE controllers, the support for various PoE
modes, and any additional logic required to coordinate power delivery across
the network infrastructure.

**Guidance:**

For simple PSE setups, including PSE PI information in the PSE controller node
might suffice due to the straightforward nature of these systems. However,
complex configurations, involving multiple components or advanced PoE features,
benefit from a dedicated PSE PI node. This method adheres to IEEE 802.3
specifications, improving documentation clarity and ensuring accurate
representation of the PoE system's complexity.

PSE PI node의 핵심 정보

PSE PI Device Tree node는 PoE system의 power delivery capability와 configuration을 정의하는 핵심 정보를 담을 수 있습니다. 이 정보는 board-level wiring과 전체 PI design에 속하므로 PSE controller node만으로 표현하기 어려울 수 있습니다.

첫째, `Powered Pairs Configuration`은 Ethernet cable에서 power를 공급하는 pair를 식별합니다. Board 설계에 맞는 pair에 전력을 넣는 데 필수이며 controller는 보통 power regulation에 집중해 physical pair 사용 정보를 모릅니다.

둘째, `Polarity of Powered Pairs`는 각 powered pair의 positive·negative polarity를 지정합니다. PD에 안전하고 효과적으로 전력을 전달하려면 필수이고 polarity 관리는 controller의 표준 기능 범위를 넘을 수 있습니다.

셋째, `PSE Cells Association`은 multi-cell 구성에서 PSE cell과 Ethernet port 또는 pair의 연결 관계를 설명합니다. 복합 system에서 power resource를 최적 배분하는 데 필요하지만 controller가 cell association을 직접 관리하지 않을 수 있습니다.

넷째, `Support for PoE Standards`는 system이 지원하는 PoE 표준과 구성을 나열하여 여러 PD와의 호환성과 표준 준수를 보장합니다. Capability는 controller 하나보다 전체 PI design에 의존할 수 있고, PI당 여러 PSE cell이 있다고 여러 PoE 표준을 자동 지원하는 것은 아닙니다.

다섯째, `Protection Mechanisms`는 overcurrent protection과 thermal management 같은 추가 보호를 설명합니다. Controller 자체 보호를 보완하는 안전·안정 기능이며 board-specific hardware나 외부 algorithm으로 구현될 수 있습니다.

PSE PI Node: Essential Information
----------------------------------

The PSE PI (Power Sourcing Equipment Power Interface) node in a device tree can
include several key pieces of information critical for defining the power
delivery capabilities and configurations of a PoE (Power over Ethernet) system.
Below is a list of such information, along with explanations for their
necessity and reasons why they might not be found within a PSE controller node:

1. **Powered Pairs Configuration**

   - *Description:* Identifies the pairs used for power delivery in the
     Ethernet cable.
   - *Necessity:* Essential to ensure the correct pairs are powered according
     to the board's design.
   - *PSE Controller Node:* Typically lacks details on physical pair usage,
     focusing on power regulation.

2. **Polarity of Powered Pairs**

   - *Description:* Specifies the polarity (positive or negative) for each
     powered pair.
   - *Necessity:* Critical for safe and effective power transmission to PDs.
   - *PSE Controller Node:* Polarity management may exceed the standard
     functionalities of PSE controllers.

3. **PSE Cells Association**

   - *Description:* Details the association of PSE cells with Ethernet ports or
     pairs in multi-cell configurations.
   - *Necessity:* Allows for optimized power resource allocation in complex
     systems.
   - *PSE Controller Node:* Controllers may not manage cell associations
     directly, focusing instead on power flow regulation.

4. **Support for PoE Standards**

   - *Description:* Lists the PoE standards and configurations supported by the
     system.
   - *Necessity:* Ensures system compatibility with various PDs and adherence
     to industry standards.
   - *PSE Controller Node:* Specific capabilities may depend on the overall PSE
     PI design rather than the controller alone. Multiple PSE cells per PI
     do not necessarily imply support for multiple PoE standards.

5. **Protection Mechanisms**

   - *Description:* Outlines additional protection mechanisms, such as
     overcurrent protection and thermal management.
   - *Necessity:* Provides extra safety and stability, complementing PSE
     controller protections.
   - *PSE Controller Node:* Some protections may be implemented via
     board-specific hardware or algorithms external to the controller.