Case Study: ATI Device
Power Management In
Windows Vista
Phil Mummah
Software Architect
ATI
Agenda
Device power management
Overview
ATI PowerPlayTM technology
Integrating with Windows Vista Power Manager
Windows Vista enhancements
Implementation details
Demo
Summary
Additional resources
Power Management
Overview
Device Run time idle detection
Transition an inactive device into a low power, non-working power state
(e.g., D2)
Wake and transition to D0 on I/O traffic, interrupt
Device-specific tradeoff of performance for reduced
power consumption
In the context of the device’s On state (D0)
Examples: scale device clock rates and core voltages, clock gating,
vary transmit power or communication speed, etc.
Device performance states
Analogous to ACPI processor performance states
Discrete combinations of power consumption and performance
Application performance tradeoff for reduced power
Reduce unnecessary activity in battery mode
Device Power Management
Opportunities and goals
Extend mobile PC battery life
Customers want extended battery life and
are willing to pay for it
Differentiate your products
Add significant value to your device
Drive down system power consumption
Reduce fan noise, system thermal output
Equally applicable to mobile and
desktop systems
Device Power Management
Opportunities and goals
Devices, services and applications all help
to reduce system power consumption
Watts
40
35
30
25
20
15
10
5
Max CPU
Max LCD
Max Animation
Min LCD
Min CPU
Max LCD
Max Animation
Min LCD
Min
Animation
Min
Animation
Device Power Management
ATI PowerPlay
Reduces the power consumption of ATI Mobile
RadeonTM graphics devices
When the device is idle
When the system is running on battery
Exposes API for OEM enhancements
Offers users the optimal balance of performance
and power consumption
ATI PowerPlayTM drives continuing
innovation and advancement in graphics
power management
Integrated with Windows Vista power management
Device Power Management
ATI PowerPlay
PowerPlay capabilities
GPU core voltage and frequency scaling
Memory clock scaling
Refresh rate reduction
PCI Express dynamic lane width switching
Thermal throttling
…and more
Windows Vista Power Policy
Benefits of integration
Offers users a seamless power
management experience
Provide unified power management controls
Allows the entire platform to respond to the
user’s current power policy
Devices automatically respond to
changing system conditions
Active power scheme/personality
AC/DC power source changes
Windows Vista Power Policy
Enhancements
Extensible power setting store
Devices or applications can define and install custom
power settings
Windows power manager stores setting data, friendly
names, values, etc.
All power settings appear in Windows
Power Options
Including custom third-party power settings
No need to provide additional configuration UI
Robust command-line tool for
system administrator
Makes testing, debugging easier
Windows Vista Power Policy
User experience improvements
Simplified power plans
Three default power plans
Power Saver, Automatic, High Performance
Indicates the overall power management
policy to the system
Each plans has a personality setting
Users can easily change the active
power plans
One-click from the desktop with the
battery meter
Windows Vista Power Policy
Steps to driver integration
Define custom power policy settings
Install custom power settings
Prepare the device driver to
Register for power events of interest
Respond appropriately to these events
Optionally, provide additional power
management UI
Implementation Details
Defining a power setting
A custom power setting definition contains
A GUID uniquely identifying the setting
Friendly name, description strings
One or more setting values
Range, e.g.,
0 – 100%
Value: 10 minutes
Discrete values
E.g., {Enabled, Disabled}; {High, Medium, Low}
Implementation Details
Defining a power setting
Critical step: Define appropriate defaults
Each power scheme personality’s defaults
Users might not change the power policy for your
power setting
System power source (AC/DC)
Each device can define multiple
power settings
Power settings can be placed in subgroups
Implementation Details
Example: Defining a power setting
GUID
{191F65B5-D45C-4a4f-8AAE-1AB8BFD980E6}
Friendly Name
“ATI Graphics Engine PowerPlay”
Description
“Configures the GPU Power Management Mode”
Values (discrete)
ATI Max Performance Mode
ATI Balanced Mode
ATI Max Battery Mode
Subgroup
New subgroup created for all ATI PowerPlay settings
Implementation Details
Installing a power setting
Add the setting and its definition to the power
policy store
Two methods supported
INF-based installation
Ideal for device drivers
New INF directives for describing power setting,
subgroup, possible values
Multiple settings can be described in the same INF file
API-based installation
Win32 APIs in Power Profiles Library (powrprof.dll)
Implementation Details
Example: Installing a power setting
[DeviceName]
AddPowerSetting=AtiPowerPolicy
Power Setting
Defined By GUID
Setting Friendly
Name, Description
[AtiPowerPolicy]
Subgroup = {2566CF20-D01A-456f-BFE1-C6C6E76D15A6},
"ATI Graphics Main Power Settings", "Set all graphics power settings "
Setting = {191F65B5-D45C-4a4f-8AAE-1AB8BFD980E6},
“ATI Graphics Engine PowerPlay Settings”, “Configures the GPU Power
Management Mode”
Value=0, "Max Battery Mode", "Minimum Power Setting", REG_DWORD, <0>
Value=1, "Balanced Mode", "Medium Power Setting", REG_DWORD, <1>
Value=2, "Max Performance Mode", "Max Power Setting", REG_DWORD, <2>
Default
Default
Default
Default
Default
Default
=
=
=
=
=
=
%GUID_MAX_POWER_SAVINGS%, %AC%, 1
%GUID_MAX_POWER_SAVINGS%, %DC%, 0
%GUID_TYPICAL_POWER_SAVINGS%, %AC%, 2
%GUID_TYPICAL_POWER_SAVINGS%, %DC%, 0
%GUID_MIN_POWER_SAVINGS%, %AC%, 2
%GUID_MIN_POWER_SAVINGS%, %DC%, 1
Discrete List of Values
Default Values for Each
Power Scheme Personality
Range of Values can also
be done, ie 0 – 100%
Implementation Details
Register for notifications
Register within device or application
initialization code
PoRegisterPowerSettingNotification()
Register with custom power setting GUID
De-register when your device is stopped
Kernel-mode registration function includes
context parameter
Most drivers will pass device extension in context
Enables drivers to handle registration for
multiple devices
Implementation Details
Example: Register for notifications
KRSContext::RegisterPowerSettingCallback(
IN PDEVICE_OBJECT DeviceObject,
OUT HANDLE
PowerSettingCallbackHandle
)
{
NTSTATUS Status = STATUS_SUCCESS;
Power Setting GUID
Status = PoRegisterPowerSettingCallback(
DeviceObject,
(LPGUID)(&GUID_GRAPHICS_ENGINE_POWER_PLAY_MODE),
(PPOWER_SETTING_CALLBACK)&PowerSettingCallback,
DeviceObject->DeviceObjectExtension,
&PowerSettingCallbackHandle
);
return Status;
}
De-register When
Device is Stopped
Implementation Details
Example: Driver callback function
NTSTATUS
PowerSettingCallback(
IN CONST LPGUID SettingGuid,
IN PULONG
NewValue,
IN ULONG
ValueLength,
IN PVOID
Context
)
{
NTSTATUS Status = STATUS_INVALID_PARAMETER;
Power Setting GUID
// Check for correct GUID, Data
if (IsEqualGUID(
(LPGUID)(&GUID_GRAPHICS_ENGINE_POWER_PLAY_MODE),
SettingGUID ) &&
(ValueLength == sizeof(DWORD)) &&
Change the Device Power
(NewValue != NULL) )
{
Management Behavior
// NOT SHOWN: Any necessary locks
// Change graphics engine power mode
}
return Status;
}
Implementation Details
Example: Deregister for notifications
NTSTATUS
UnRegisterPowerSettingCallback(
IN HANDLE PowerSettingCallbackHandle
)
{
NTSTATUS Status = STATUS_SUCCESS;
Status = PoUnRegisterPowerSettingCallback(
&PowerSettingCallbackHandle
);
return Status;
}
Implementation Details
Power configuration user interface
Default power
settings
Note:
Power settings
may be
system-specific
Implementation Details
Power configuration user interface
UI extended
with custom
power settings
Implementation Details
User interface summary
Windows automatically
adds custom power
settings to Power Options
Advanced Settings UI
Multiple settings
can be contained
in a new subgroup
Each setting has
an AC and DC value
Settings can be
discrete or range
of values
Implementation Details
Power configuration user interface
UI extended
with additional
property sheet
Implementation Details
User interface summary
Property sheets may
be added for more
advanced UI
May have a superset
of functionality
E.g., battery
degrade behaviors
Property sheets
can leverage Power
Policy APIs
ATI exposes PowerPlay
functionality
OEM does not
need to write special
UI to add features
Integrating PowerPlay
With Windows Vista
Phil Mummah
SW Architect
ATI
Call To Action
Implement device power management
technologies in your hardware designs
Take advantage of Windows Vista power
management integration opportunities
Review Integrating with Windows Vista
Power Policy white paper
http://go.microsoft.com/fwlink/?LinkId=51286
Additional Resources
ATI Technologies, Inc.
http://www.ati.com
ATI PowerPlayTM white paper
http://www.ati.com/products/pdf/powerplaywp2.pdf
Windows Hardware and Driver Central
http://www.microsoft.com/whdc
Power Management, ACPI on WHDC
http://www.microsoft.com/whdc/system/pnppwr/powermgmt/
default.mspx
Integrating with Windows Vista Power Policy
white paper
http://go.microsoft.com/fwlink/?LinkId=51286
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