On 19/07/18 12:56, Takashi Iwai wrote:
On Thu, 19 Jul 2018 13:22:11 +0200,
Jorge Sanjuan wrote:
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 (?).
Can it be tied with runtime PM?
Sure. I think that could work. So the snd-usb driver would only attempt
to drop a Power Domain from D0 to D1 only if (dev->power.runtime_auto ==
true)? Is there any clean way to check for that? I couldn't find any
helper function.
The change to D2 state is already wrapped in runtime PM as usb_driver
.suspend callback only gets called when runtime PM is enabled from sysfs.
Thanks,
Jorge
Need to read through your patchset at first...
thanks,
Takashi
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
--
2.11.0
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