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Date:   Thu, 19 Jul 2018 13:56:30 +0200
Message-ID: <s5hlga78mmp.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Jorge Sanjuan <jorge.sanjuan@codethink.co.uk>
Cc:     alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/4] usb-audio: Add UAC3 Power Domains
In-Reply-To: <20180719112215.4219-1-jorge.sanjuan@codethink.co.uk>
References: <20180719112215.4219-1-jorge.sanjuan@codethink.co.uk>
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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?

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
>