+++ /dev/null
-<!-- Copyright (C) 2003 Red Hat, Inc. -->
-<!-- This material may be distributed only subject to the terms -->
-<!-- and conditions set forth in the Open Publication License, v1.0 -->
-<!-- or later (the latest version is presently available at -->
-<!-- http://www.opencontent.org/openpub/). -->
-<!-- Distribution of the work or derivative of the work in any -->
-<!-- standard (paper) book form is prohibited unless prior -->
-<!-- permission is obtained from the copyright holder. -->
-<HTML
-><HEAD
-><TITLE
->Changing Power Modes</TITLE
-><meta name="MSSmartTagsPreventParsing" content="TRUE">
-<META
-NAME="GENERATOR"
-CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
-"><LINK
-REL="HOME"
-TITLE="eCos Reference Manual"
-HREF="ecos-ref.html"><LINK
-REL="UP"
-TITLE="eCos Power Management Support"
-HREF="services-power.html"><LINK
-REL="PREVIOUS"
-TITLE="Power Management Information"
-HREF="power-info.html"><LINK
-REL="NEXT"
-TITLE="Support for Policy Modules"
-HREF="power-policy.html"></HEAD
-><BODY
-CLASS="REFENTRY"
-BGCOLOR="#FFFFFF"
-TEXT="#000000"
-LINK="#0000FF"
-VLINK="#840084"
-ALINK="#0000FF"
-><DIV
-CLASS="NAVHEADER"
-><TABLE
-SUMMARY="Header navigation table"
-WIDTH="100%"
-BORDER="0"
-CELLPADDING="0"
-CELLSPACING="0"
-><TR
-><TH
-COLSPAN="3"
-ALIGN="center"
->eCos Reference Manual</TH
-></TR
-><TR
-><TD
-WIDTH="10%"
-ALIGN="left"
-VALIGN="bottom"
-><A
-HREF="power-info.html"
-ACCESSKEY="P"
->Prev</A
-></TD
-><TD
-WIDTH="80%"
-ALIGN="center"
-VALIGN="bottom"
-></TD
-><TD
-WIDTH="10%"
-ALIGN="right"
-VALIGN="bottom"
-><A
-HREF="power-policy.html"
-ACCESSKEY="N"
->Next</A
-></TD
-></TR
-></TABLE
-><HR
-ALIGN="LEFT"
-WIDTH="100%"></DIV
-><H1
-><A
-NAME="POWER-CHANGE">Changing Power Modes</H1
-><DIV
-CLASS="REFNAMEDIV"
-><A
-NAME="AEN15752"
-></A
-><H2
->Name</H2
->Changing Power Modes -- reducing or increasing power consumption as needed</DIV
-><DIV
-CLASS="REFSYNOPSISDIV"
-><A
-NAME="AEN15755"><H2
->Synopsis</H2
-><DIV
-CLASS="FUNCSYNOPSIS"
-><A
-NAME="AEN15756"><P
-></P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="FUNCSYNOPSISINFO"
->#include <cyg/power/power.h></PRE
-></TD
-></TR
-></TABLE
-><P
-><CODE
-><CODE
-CLASS="FUNCDEF"
-> void power_set_mode
- </CODE
->( PowerMode new_mode
- );</CODE
-></P
-><P
-><CODE
-><CODE
-CLASS="FUNCDEF"
-> void power_set_controller_mode
- </CODE
->( PowerController* controller
- , PowerMode new_mode
- );</CODE
-></P
-><P
-><CODE
-><CODE
-CLASS="FUNCDEF"
-> void power_set_controller_mode_now
- </CODE
->( PowerController* controller
- , PowerMode new_mode
- );</CODE
-></P
-><P
-></P
-></DIV
-></DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="POWER-CHANGE-GLOBAL"
-></A
-><H2
->Changing the Global Power Mode</H2
-><P
->The primary functionality supported by the power management package is
-to change the system's global power mode. This is achieved by calling
-the function <TT
-CLASS="FUNCTION"
->power_set_mode</TT
-> with a single
-argument, which should be one of <TT
-CLASS="LITERAL"
->PowerMode_Active</TT
->,
-<TT
-CLASS="LITERAL"
->PowerMode_Idle</TT
->, <TT
-CLASS="LITERAL"
->PowerMode_Sleep</TT
->
-or <TT
-CLASS="LITERAL"
->PowerMode_Off</TT
->. Typically this function will only
-be invoked in certain scenarios:</P
-><P
-></P
-><OL
-TYPE="1"
-><LI
-><P
->A typical system will contain a policy module which is primarily
-responsible for initiating power mode changes, and a thread inside the
-power management package. The policy module will call
-<TT
-CLASS="FUNCTION"
->power_set_mode</TT
->, which has the effect of
-manipulating some internal state in the power management package and
-waking up its thread. When this thread gets scheduled to run (its
-priority is controlled by a configuration option), it will iterate
-over the power controllers and invoke each controller to change its
-power mode. There is support for a <A
-HREF="power-policy.html#POWER-POLICY-CALLBACK"
->callback function</A
->, and for
-<A
-HREF="power-attached.html"
->detached</A
-> power controllers.</P
-></LI
-><LI
-><P
->After a call to <TT
-CLASS="FUNCTION"
->power_set_mode</TT
-> but before the
-power management thread has had a chance to iterate over all the
-controllers, or even before the thread has been rescheduled at all,
-the policy module may decide that a different power mode would be more
-appropriate for the current situation and calls
-<TT
-CLASS="FUNCTION"
->power_set_mode</TT
-> again. This has the effect of
-aborting the previous mode change, followed by the power management
-thread iterating over the power controllers again for the new mode.</P
-></LI
-><LI
-><P
->If there is no single policy module responsible for power mode
-changes, any code can call <TT
-CLASS="FUNCTION"
->power_set_mode</TT
->. If
-there are multiple calls in quick succession, earlier calls will
-be aborted and the system should end up in the power mode
-corresponding to the last call</P
-></LI
-><LI
-><P
->As a special case, it is possible for a power controller to call
-<TT
-CLASS="FUNCTION"
->power_set_mode</TT
-> when invoked by the power
-management thread. For example a power controller could decide that it
-is inappropriate for the system to go to sleep because the device it
-is associated with is still busy. The effect is as if the policy
-module had called <TT
-CLASS="FUNCTION"
->power_set_mode</TT
-> again before
-the mode change had completed.</P
-></LI
-></OL
-><P
->If the power management package has been configured not to use a
-separate thread then obviously the behaviour is somewhat different.
-The call to <TT
-CLASS="FUNCTION"
->power_set_mode</TT
-> will now iterate over
-the various power controllers immediately, rather than leaving this to
-a separate thread, and the whole mode change completes before
-<TT
-CLASS="FUNCTION"
->power_set_mode</TT
-> returns. If some other thread or a
-DSR calls <TT
-CLASS="FUNCTION"
->power_set_mode</TT
-> concurrently the
-behaviour of the system is undefined. However, it is still legal for a
-power controller to call <TT
-CLASS="FUNCTION"
->power_set_mode</TT
->:
-effectively this is a recursive call; it is detected by the system,
-and internal state is updated; the recursive
-<TT
-CLASS="FUNCTION"
->power_set_mode</TT
-> call now returns, and when the
-power controller returns back to the original
-<TT
-CLASS="FUNCTION"
->power_set_mode</TT
-> call it detects what has happened,
-aborts the previous mode change, and starts a new mode change as
-requested by the controller.</P
-><P
-><TT
-CLASS="FUNCTION"
->power_set_mode</TT
-> is normally invoked from thread
-context. If a separate power management thread is used it can be
-invoked safely from DSR context. If the system is configured not to
-use such a thread, it may or may not be safe to invoke this function
-from DSR context: essentially the function just iterates through
-the various power controllers, and the documentation or source code of
-each controller present in the current system will have to be examined
-to determine whether or not this can happen safely in DSR context.
-<TT
-CLASS="FUNCTION"
->power_set_mode</TT
-> should never be invoked from
-ISR context.</P
-></DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="POWER-CHANGE-CONTROLLER"
-></A
-><H2
->Manipulating an Individual Power Controller</H2
-><P
->In some cases it is desirable to set the power mode of an individual
-controller separately from the mode for the system as a whole. For
-example if a device is not currently being used then the associated
-power controller could be set to <TT
-CLASS="LITERAL"
->PowerMode_Off</TT
->,
-even while the system as a whole is still active. This can be achieved
-by calling the function
-<TT
-CLASS="FUNCTION"
->power_set_controller_mode</TT
->. It takes two
-arguments: the first identifies a particular controller; the second
-specifies the desired new power mode for that controller. The function
-operates in much the same way as <TT
-CLASS="FUNCTION"
->power_set_mode</TT
->,
-for example if a separate power management thread is being used then
-<TT
-CLASS="FUNCTION"
->power_set_controller_mode</TT
-> operates by
-manipulating some internal state and waking up that thread. The
-limitations are also much the same as for
-<TT
-CLASS="FUNCTION"
->power_set_mode</TT
->, so for example
-<TT
-CLASS="FUNCTION"
->power_set_controller_mode</TT
-> should not be invoked
-from inside ISRs.</P
-><P
->Manipulating individual controllers is often used in conjunction with
-the function <A
-HREF="power-attached.html"
-><TT
-CLASS="FUNCTION"
->power_set_controller_attached</TT
-></A
->,
-allowing the policy module to specify which controllers are affected
-by global mode changes.</P
-></DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="POWER-CHANGE-CONTROLLER-NOW"
-></A
-><H2
->Direct Manipulation of a Power Controller</H2
-><P
->In exceptional circumstances it may be necessary to invoke a power
-controller directly, bypassing the power management thread and
-higher-level functionality such as <A
-HREF="power-policy.html#POWER-POLICY-CALLBACK"
->callback functions</A
->. The
-function <TT
-CLASS="FUNCTION"
->power_set_controller_mode_now</TT
-> allows
-this. It takes two arguments, a controller and a mode, just like
-<TT
-CLASS="FUNCTION"
->power_set_controller_mode</TT
->.</P
-><P
->Use of <TT
-CLASS="FUNCTION"
->power_set_controller_mode_now</TT
-> is
-dangerous. For example no attempt is made to synchronise with any
-other power mode changes that might be happening concurrently. A
-possible use is when the system gets woken up out of
-<SPAN
-CLASS="TYPE"
->sleep</SPAN
-> mode: depending on the hardware, on which power
-controllers are present, and on the application code it may be
-necessary to wake up some power controllers immediately before the
-system as a whole is ready to run again.</P
-></DIV
-><DIV
-CLASS="NAVFOOTER"
-><HR
-ALIGN="LEFT"
-WIDTH="100%"><TABLE
-SUMMARY="Footer navigation table"
-WIDTH="100%"
-BORDER="0"
-CELLPADDING="0"
-CELLSPACING="0"
-><TR
-><TD
-WIDTH="33%"
-ALIGN="left"
-VALIGN="top"
-><A
-HREF="power-info.html"
-ACCESSKEY="P"
->Prev</A
-></TD
-><TD
-WIDTH="34%"
-ALIGN="center"
-VALIGN="top"
-><A
-HREF="ecos-ref.html"
-ACCESSKEY="H"
->Home</A
-></TD
-><TD
-WIDTH="33%"
-ALIGN="right"
-VALIGN="top"
-><A
-HREF="power-policy.html"
-ACCESSKEY="N"
->Next</A
-></TD
-></TR
-><TR
-><TD
-WIDTH="33%"
-ALIGN="left"
-VALIGN="top"
->Power Management Information</TD
-><TD
-WIDTH="34%"
-ALIGN="center"
-VALIGN="top"
-><A
-HREF="services-power.html"
-ACCESSKEY="U"
->Up</A
-></TD
-><TD
-WIDTH="33%"
-ALIGN="right"
-VALIGN="top"
->Support for Policy Modules</TD
-></TR
-></TABLE
-></DIV
-></BODY
-></HTML
->
\ No newline at end of file
projects / karo-tx-redboot.git / blobdiff