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diff --git a/Documentation/networking/pse-pd/pse-pi.rst b/Documentation/networking/pse-pd/pse-pi.rst new file mode 100644 index 000000000000..5cad14fedc13 --- /dev/null +++ b/Documentation/networking/pse-pd/pse-pi.rst @@ -0,0 +1,301 @@ +.. 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. + +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. + +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. + +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 | + | | + +--------------------------+ + +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 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 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. |