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-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
-
-<book id="regulator-api">
- <bookinfo>
- <title>Voltage and current regulator API</title>
-
- <authorgroup>
- <author>
- <firstname>Liam</firstname>
- <surname>Girdwood</surname>
- <affiliation>
- <address>
- <email>lrg@slimlogic.co.uk</email>
- </address>
- </affiliation>
- </author>
- <author>
- <firstname>Mark</firstname>
- <surname>Brown</surname>
- <affiliation>
- <orgname>Wolfson Microelectronics</orgname>
- <address>
- <email>broonie@opensource.wolfsonmicro.com</email>
- </address>
- </affiliation>
- </author>
- </authorgroup>
-
- <copyright>
- <year>2007-2008</year>
- <holder>Wolfson Microelectronics</holder>
- </copyright>
- <copyright>
- <year>2008</year>
- <holder>Liam Girdwood</holder>
- </copyright>
-
- <legalnotice>
- <para>
- This documentation is free software; you can redistribute
- it and/or modify it under the terms of the GNU General Public
- License version 2 as published by the Free Software Foundation.
- </para>
-
- <para>
- This program is distributed in the hope that it will be
- useful, but WITHOUT ANY WARRANTY; without even the implied
- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
- See the GNU General Public License for more details.
- </para>
-
- <para>
- You should have received a copy of the GNU General Public
- License along with this program; if not, write to the Free
- Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
- MA 02111-1307 USA
- </para>
-
- <para>
- For more details see the file COPYING in the source
- distribution of Linux.
- </para>
- </legalnotice>
- </bookinfo>
-
-<toc></toc>
-
- <chapter id="intro">
- <title>Introduction</title>
- <para>
- This framework is designed to provide a standard kernel
- interface to control voltage and current regulators.
- </para>
- <para>
- The intention is to allow systems to dynamically control
- regulator power output in order to save power and prolong
- battery life. This applies to both voltage regulators (where
- voltage output is controllable) and current sinks (where current
- limit is controllable).
- </para>
- <para>
- Note that additional (and currently more complete) documentation
- is available in the Linux kernel source under
- <filename>Documentation/power/regulator</filename>.
- </para>
-
- <sect1 id="glossary">
- <title>Glossary</title>
- <para>
- The regulator API uses a number of terms which may not be
- familiar:
- </para>
- <glossary>
-
- <glossentry>
- <glossterm>Regulator</glossterm>
- <glossdef>
- <para>
- Electronic device that supplies power to other devices. Most
- regulators can enable and disable their output and some can also
- control their output voltage or current.
- </para>
- </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm>Consumer</glossterm>
- <glossdef>
- <para>
- Electronic device which consumes power provided by a regulator.
- These may either be static, requiring only a fixed supply, or
- dynamic, requiring active management of the regulator at
- runtime.
- </para>
- </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm>Power Domain</glossterm>
- <glossdef>
- <para>
- The electronic circuit supplied by a given regulator, including
- the regulator and all consumer devices. The configuration of
- the regulator is shared between all the components in the
- circuit.
- </para>
- </glossdef>
- </glossentry>
-
- <glossentry>
- <glossterm>Power Management Integrated Circuit</glossterm>
- <acronym>PMIC</acronym>
- <glossdef>
- <para>
- An IC which contains numerous regulators and often also other
- subsystems. In an embedded system the primary PMIC is often
- equivalent to a combination of the PSU and southbridge in a
- desktop system.
- </para>
- </glossdef>
- </glossentry>
- </glossary>
- </sect1>
- </chapter>
-
- <chapter id="consumer">
- <title>Consumer driver interface</title>
- <para>
- This offers a similar API to the kernel clock framework.
- Consumer drivers use <link
- linkend='API-regulator-get'>get</link> and <link
- linkend='API-regulator-put'>put</link> operations to acquire and
- release regulators. Functions are
- provided to <link linkend='API-regulator-enable'>enable</link>
- and <link linkend='API-regulator-disable'>disable</link> the
- reguator and to get and set the runtime parameters of the
- regulator.
- </para>
- <para>
- When requesting regulators consumers use symbolic names for their
- supplies, such as "Vcc", which are mapped into actual regulator
- devices by the machine interface.
- </para>
- <para>
- A stub version of this API is provided when the regulator
- framework is not in use in order to minimise the need to use
- ifdefs.
- </para>
-
- <sect1 id="consumer-enable">
- <title>Enabling and disabling</title>
- <para>
- The regulator API provides reference counted enabling and
- disabling of regulators. Consumer devices use the <function><link
- linkend='API-regulator-enable'>regulator_enable</link></function>
- and <function><link
- linkend='API-regulator-disable'>regulator_disable</link>
- </function> functions to enable and disable regulators. Calls
- to the two functions must be balanced.
- </para>
- <para>
- Note that since multiple consumers may be using a regulator and
- machine constraints may not allow the regulator to be disabled
- there is no guarantee that calling
- <function>regulator_disable</function> will actually cause the
- supply provided by the regulator to be disabled. Consumer
- drivers should assume that the regulator may be enabled at all
- times.
- </para>
- </sect1>
-
- <sect1 id="consumer-config">
- <title>Configuration</title>
- <para>
- Some consumer devices may need to be able to dynamically
- configure their supplies. For example, MMC drivers may need to
- select the correct operating voltage for their cards. This may
- be done while the regulator is enabled or disabled.
- </para>
- <para>
- The <function><link
- linkend='API-regulator-set-voltage'>regulator_set_voltage</link>
- </function> and <function><link
- linkend='API-regulator-set-current-limit'
- >regulator_set_current_limit</link>
- </function> functions provide the primary interface for this.
- Both take ranges of voltages and currents, supporting drivers
- that do not require a specific value (eg, CPU frequency scaling
- normally permits the CPU to use a wider range of supply
- voltages at lower frequencies but does not require that the
- supply voltage be lowered). Where an exact value is required
- both minimum and maximum values should be identical.
- </para>
- </sect1>
-
- <sect1 id="consumer-callback">
- <title>Callbacks</title>
- <para>
- Callbacks may also be <link
- linkend='API-regulator-register-notifier'>registered</link>
- for events such as regulation failures.
- </para>
- </sect1>
- </chapter>
-
- <chapter id="driver">
- <title>Regulator driver interface</title>
- <para>
- Drivers for regulator chips <link
- linkend='API-regulator-register'>register</link> the regulators
- with the regulator core, providing operations structures to the
- core. A <link
- linkend='API-regulator-notifier-call-chain'>notifier</link> interface
- allows error conditions to be reported to the core.
- </para>
- <para>
- Registration should be triggered by explicit setup done by the
- platform, supplying a <link
- linkend='API-struct-regulator-init-data'>struct
- regulator_init_data</link> for the regulator containing
- <link linkend='machine-constraint'>constraint</link> and
- <link linkend='machine-supply'>supply</link> information.
- </para>
- </chapter>
-
- <chapter id="machine">
- <title>Machine interface</title>
- <para>
- This interface provides a way to define how regulators are
- connected to consumers on a given system and what the valid
- operating parameters are for the system.
- </para>
-
- <sect1 id="machine-supply">
- <title>Supplies</title>
- <para>
- Regulator supplies are specified using <link
- linkend='API-struct-regulator-consumer-supply'>struct
- regulator_consumer_supply</link>. This is done at
- <link linkend='driver'>driver registration
- time</link> as part of the machine constraints.
- </para>
- </sect1>
-
- <sect1 id="machine-constraint">
- <title>Constraints</title>
- <para>
- As well as defining the connections the machine interface
- also provides constraints defining the operations that
- clients are allowed to perform and the parameters that may be
- set. This is required since generally regulator devices will
- offer more flexibility than it is safe to use on a given
- system, for example supporting higher supply voltages than the
- consumers are rated for.
- </para>
- <para>
- This is done at <link linkend='driver'>driver
- registration time</link> by providing a <link
- linkend='API-struct-regulation-constraints'>struct
- regulation_constraints</link>.
- </para>
- <para>
- The constraints may also specify an initial configuration for the
- regulator in the constraints, which is particularly useful for
- use with static consumers.
- </para>
- </sect1>
- </chapter>
-
- <chapter id="api">
- <title>API reference</title>
- <para>
- Due to limitations of the kernel documentation framework and the
- existing layout of the source code the entire regulator API is
- documented here.
- </para>
-!Iinclude/linux/regulator/consumer.h
-!Iinclude/linux/regulator/machine.h
-!Iinclude/linux/regulator/driver.h
-!Edrivers/regulator/core.c
- </chapter>
-</book>