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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 definining the connections the machine interface
+ also provides constraints definining 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>
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