linux-kernel - [PATCH v2 15/15] docs: Add PECI documentation

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Message-Id: <20210803113134.2262882-16-iwona.winiarska@intel.com>
Date:   Tue,  3 Aug 2021 13:31:34 +0200
From:   Iwona Winiarska <iwona.winiarska@...el.com>
To:     linux-kernel@...r.kernel.org, openbmc@...ts.ozlabs.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     x86@...nel.org, devicetree@...r.kernel.org,
        linux-aspeed@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org, linux-hwmon@...r.kernel.org,
        linux-doc@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Joel Stanley <joel@....id.au>,
        Andrew Jeffery <andrew@...id.au>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
        Jonathan Corbet <corbet@....net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Yazen Ghannam <yazen.ghannam@....com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Jae Hyun Yoo <jae.hyun.yoo@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Zev Weiss <zweiss@...inix.com>,
        David Muller <d.mueller@...oft.ch>,
        Iwona Winiarska <iwona.winiarska@...el.com>
Subject: [PATCH v2 15/15] docs: Add PECI documentation

Add a brief overview of PECI and PECI wire interface.
The documentation also contains kernel-doc for PECI subsystem internals
and PECI CPU Driver API.

Signed-off-by: Iwona Winiarska <iwona.winiarska@...el.com>
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
---
 Documentation/index.rst      |  1 +
 Documentation/peci/index.rst | 16 ++++++++++++
 Documentation/peci/peci.rst  | 48 ++++++++++++++++++++++++++++++++++++
 MAINTAINERS                  |  1 +
 4 files changed, 66 insertions(+)
 create mode 100644 Documentation/peci/index.rst
 create mode 100644 Documentation/peci/peci.rst

diff --git a/Documentation/index.rst b/Documentation/index.rst
index 54ce34fd6fbd..7671f2cd474f 100644
--- a/Documentation/index.rst
+++ b/Documentation/index.rst
@@ -137,6 +137,7 @@ needed).
    misc-devices/index
    scheduler/index
    mhi/index
+   peci/index
 
 Architecture-agnostic documentation
 -----------------------------------
diff --git a/Documentation/peci/index.rst b/Documentation/peci/index.rst
new file mode 100644
index 000000000000..989de10416e7
--- /dev/null
+++ b/Documentation/peci/index.rst
@@ -0,0 +1,16 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+====================
+Linux PECI Subsystem
+====================
+
+.. toctree::
+
+   peci
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`
diff --git a/Documentation/peci/peci.rst b/Documentation/peci/peci.rst
new file mode 100644
index 000000000000..a12c8e10c4a9
--- /dev/null
+++ b/Documentation/peci/peci.rst
@@ -0,0 +1,48 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+========
+Overview
+========
+
+The Platform Environment Control Interface (PECI) is a communication
+interface between Intel processor and management controllers
+(e.g. Baseboard Management Controller, BMC).
+PECI provides services that allow the management controller to
+configure, monitor and debug platform by accessing various registers.
+It defines a dedicated command protocol, where the management
+controller is acting as a PECI originator and the processor - as
+a PECI responder.
+PECI can be used in both single processor and multiple-processor based
+systems.
+
+NOTE:
+Intel PECI specification is not released as a dedicated document,
+instead it is a part of External Design Specification (EDS) for given
+Intel CPU. External Design Specifications are usually not publicly
+available.
+
+PECI Wire
+---------
+
+PECI Wire interface uses a single wire for self-clocking and data
+transfer. It does not require any additional control lines - the
+physical layer is a self-clocked one-wire bus signal that begins each
+bit with a driven, rising edge from an idle near zero volts. The
+duration of the signal driven high allows to determine whether the bit
+value is logic '0' or logic '1'. PECI Wire also includes variable data
+rate established with every message.
+
+For PECI Wire, each processor package will utilize unique, fixed
+addresses within a defined range and that address should
+have a fixed relationship with the processor socket ID - if one of the
+processors is removed, it does not affect addresses of remaining
+processors.
+
+PECI subsystem internals
+------------------------
+
+.. kernel-doc:: include/linux/peci.h
+
+PECI CPU Driver API
+-------------------
+.. kernel-doc:: include/linux/peci-cpu.h
diff --git a/MAINTAINERS b/MAINTAINERS
index 4861a214d9fe..c50d4d0005e3 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14527,6 +14527,7 @@ R:	Jae Hyun Yoo <jae.hyun.yoo@...ux.intel.com>
 L:	openbmc@...ts.ozlabs.org (moderated for non-subscribers)
 S:	Supported
 F:	Documentation/devicetree/bindings/peci/
+F:	Documentation/peci/
 F:	drivers/peci/
 F:	include/linux/peci-cpu.h
 F:	include/linux/peci.h
-- 
2.31.1