Intel® High Definition Audio Low Power Capabilities: Spec
Title: Low Power Capabilities Clarifications and Enhancements
Brief description of the functional changes:
This change of the specification will allow the power to be reduced when devices or the “codec” as a whole is not active. The challenges with the current version of the Intel® High Definition Audio Specification include:
1) Inability to put the codec into low power state as the ability to report jack presence state changes is not clearly called out and is thus not implemented in typical codecs today
2) Clarity for how to use low power states was missing, regarding the reporting of Unsolicited Responses and the ability to wake the system if in low power system states did not exist
3) Requirements on what is expected, such as no audio artifacts, and ability to go into low power states was not specified and thus most codecs did not implement sufficient capabilities for states below D0 to be used. As a result, codec low power states were typically not used (were disabled) in the past.
4) Lack of clarity on what happens to settings that have been changed across power states and resets.
This set of changes provides a clarification to controlling power at the widget level, adds a requirement to not pop or click when changing power states and also provides for an override function for nodes that support power state controls, but not the Supported Power States parameter.
This set of changes also clarifies the required operation for Jack presence detection and audio streams not coming from or going to the HD Audio link behave during power states other than fully on and during transitions.
Read the full Intel® High Definition Audio Low Power Capabilities Specification.