171 lines
5.9 KiB
ReStructuredText
171 lines
5.9 KiB
ReStructuredText
.. Copyright 2007-2008 Wolfson Microelectronics
|
|
|
|
.. 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.
|
|
|
|
=================================
|
|
Voltage and current regulator API
|
|
=================================
|
|
|
|
:Author: Liam Girdwood
|
|
:Author: Mark Brown
|
|
|
|
Introduction
|
|
============
|
|
|
|
This framework is designed to provide a standard kernel interface to
|
|
control voltage and current regulators.
|
|
|
|
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).
|
|
|
|
Note that additional (and currently more complete) documentation is
|
|
available in the Linux kernel source under
|
|
``Documentation/power/regulator``.
|
|
|
|
Glossary
|
|
--------
|
|
|
|
The regulator API uses a number of terms which may not be familiar:
|
|
|
|
Regulator
|
|
|
|
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.
|
|
|
|
Consumer
|
|
|
|
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.
|
|
|
|
Power Domain
|
|
|
|
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.
|
|
|
|
Power Management Integrated Circuit (PMIC)
|
|
|
|
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.
|
|
|
|
Consumer driver interface
|
|
=========================
|
|
|
|
This offers a similar API to the kernel clock framework. Consumer
|
|
drivers use `get <#API-regulator-get>`__ and
|
|
`put <#API-regulator-put>`__ operations to acquire and release
|
|
regulators. Functions are provided to `enable <#API-regulator-enable>`__
|
|
and `disable <#API-regulator-disable>`__ the regulator and to get and
|
|
set the runtime parameters of the regulator.
|
|
|
|
When requesting regulators consumers use symbolic names for their
|
|
supplies, such as "Vcc", which are mapped into actual regulator devices
|
|
by the machine interface.
|
|
|
|
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.
|
|
|
|
Enabling and disabling
|
|
----------------------
|
|
|
|
The regulator API provides reference counted enabling and disabling of
|
|
regulators. Consumer devices use the :c:func:`regulator_enable()` and
|
|
:c:func:`regulator_disable()` functions to enable and disable
|
|
regulators. Calls to the two functions must be balanced.
|
|
|
|
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 :c:func:`regulator_disable()` 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.
|
|
|
|
Configuration
|
|
-------------
|
|
|
|
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.
|
|
|
|
The :c:func:`regulator_set_voltage()` and
|
|
:c:func:`regulator_set_current_limit()` 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.
|
|
|
|
Callbacks
|
|
---------
|
|
|
|
Callbacks may also be registered for events such as regulation failures.
|
|
|
|
Regulator driver interface
|
|
==========================
|
|
|
|
Drivers for regulator chips register the regulators with the regulator
|
|
core, providing operations structures to the core. A notifier interface
|
|
allows error conditions to be reported to the core.
|
|
|
|
Registration should be triggered by explicit setup done by the platform,
|
|
supplying a struct :c:type:`regulator_init_data` for the regulator
|
|
containing constraint and supply information.
|
|
|
|
Machine interface
|
|
=================
|
|
|
|
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.
|
|
|
|
Supplies
|
|
--------
|
|
|
|
Regulator supplies are specified using struct
|
|
:c:type:`regulator_consumer_supply`. This is done at driver registration
|
|
time as part of the machine constraints.
|
|
|
|
Constraints
|
|
-----------
|
|
|
|
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.
|
|
|
|
This is done at driver registration time` by providing a
|
|
struct :c:type:`regulation_constraints`.
|
|
|
|
The constraints may also specify an initial configuration for the
|
|
regulator in the constraints, which is particularly useful for use with
|
|
static consumers.
|
|
|
|
API reference
|
|
=============
|
|
|
|
Due to limitations of the kernel documentation framework and the
|
|
existing layout of the source code the entire regulator API is
|
|
documented here.
|
|
|
|
.. kernel-doc:: include/linux/regulator/consumer.h
|
|
:internal:
|
|
|
|
.. kernel-doc:: include/linux/regulator/machine.h
|
|
:internal:
|
|
|
|
.. kernel-doc:: include/linux/regulator/driver.h
|
|
:internal:
|
|
|
|
.. kernel-doc:: drivers/regulator/core.c
|
|
:export:
|