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1.. SPDX-License-Identifier: GPL-2.0-only2 3========4Overview5========6 7The Platform Environment Control Interface (PECI) is a communication8interface between Intel processor and management controllers9(e.g. Baseboard Management Controller, BMC).10PECI provides services that allow the management controller to11configure, monitor and debug platform by accessing various registers.12It defines a dedicated command protocol, where the management13controller is acting as a PECI originator and the processor - as14a PECI responder.15PECI can be used in both single processor and multiple-processor based16systems.17 18NOTE:19Intel PECI specification is not released as a dedicated document,20instead it is a part of External Design Specification (EDS) for given21Intel CPU. External Design Specifications are usually not publicly22available.23 24PECI Wire25---------26 27PECI Wire interface uses a single wire for self-clocking and data28transfer. It does not require any additional control lines - the29physical layer is a self-clocked one-wire bus signal that begins each30bit with a driven, rising edge from an idle near zero volts. The31duration of the signal driven high allows to determine whether the bit32value is logic '0' or logic '1'. PECI Wire also includes variable data33rate established with every message.34 35For PECI Wire, each processor package will utilize unique, fixed36addresses within a defined range and that address should37have a fixed relationship with the processor socket ID - if one of the38processors is removed, it does not affect addresses of remaining39processors.40 41PECI subsystem internals42------------------------43 44.. kernel-doc:: include/linux/peci.h45.. kernel-doc:: drivers/peci/internal.h46.. kernel-doc:: drivers/peci/core.c47.. kernel-doc:: drivers/peci/request.c48 49PECI CPU Driver API50-------------------51.. kernel-doc:: drivers/peci/cpu.c52