This patchset add support for UAC3 Power Domains. This feature of the USB audio class 3 allows the host to notify the device what it is making use of so power comsumption can be optimized.
This proposal implements this feature for Power Domains that include an Input/Output Terminal associated to an audio Streaming interface. This is the main usage of this feature according to the spec. For that reason, the logic for the Power Domain state change has been implemented within the ALSA PCMs logic and the suspend/resume callbacks of the usb_driver. The behaviour would be as follows:
* Power Domain State D0: A Power Domain will reach this state only when the audio substream associated to that domain is being used (i,e. Audio playback/capture is happening). * Power Domain State D1: This is the Idle state where the driver is going to always want to be in order to reduce power consumption. * Power Domain State D2: This state is only set when the usb driver asumes the device is not going to be used anymore and hence, it wont care about getting any interrupts from the device. This will only happen when power level is set to "auto" in sysfs so the usb driver gets suspended when the interfaces are not in use.
NOTE: The way this has been implemented will always try to put the Power Domain in state D1 if the Power Domain exists so there is not a way a user could disable this feature. It may be worth getting a control exposed to userland that enables/disables this feature (?).
Power Domains affecting other units independently are required to be bypassed via a Selector Unit first before the host can change the power state. This sceneario is not covered in this patchset.
based on next-20180719
Jorge Sanjuan (4): ALSA: usb-audio: Initial Power Domain support ALSA: usb-audio: AudioStreaming Power Domain parsing ALSA: usb-audio: Operate UAC3 Power Domains in PCM callbacks ALSA: usb-audio: Add UAC3 Power Domains to suspend/resume
include/linux/usb/audio-v3.h | 4 ++ sound/usb/Makefile | 1 + sound/usb/card.c | 9 ++++ sound/usb/card.h | 2 + sound/usb/pcm.c | 64 +++++++++++++++++++++-- sound/usb/pcm.h | 2 + sound/usb/power.c | 117 +++++++++++++++++++++++++++++++++++++++++++ sound/usb/power.h | 19 +++++++ sound/usb/stream.c | 70 +++++++++++++++++++++++--- 9 files changed, 277 insertions(+), 11 deletions(-) create mode 100644 sound/usb/power.c