mirror of
https://github.com/edk2-porting/linux-next.git
synced 2024-12-21 11:44:01 +08:00
25985edced
Fixes generated by 'codespell' and manually reviewed. Signed-off-by: Lucas De Marchi <lucas.demarchi@profusion.mobi>
305 lines
9.8 KiB
XML
305 lines
9.8 KiB
XML
<?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>
|