linux-kernel - Re: [PATCH v3 0/4] usb-audio: Add UAC3 Power Domains

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Message-ID: <s5hlg9rpn15.wl-tiwai@suse.de>
Date:   Tue, 31 Jul 2018 15:12:06 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Jorge Sanjuan <jorge.sanjuan@...ethink.co.uk>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/4] usb-audio: Add UAC3 Power Domains

On Tue, 31 Jul 2018 14:28:41 +0200,
Jorge Sanjuan wrote:
> 
> This is what's new in this v3:
>  - Add proper SPDX identifier for new source file.
>  - Add delay unit in comment for BADD inferred recovery
>    times and specify the actual delay time for them.
>  - Suspend the usb stream *after* alsa has supended its stuff.
>  - Make sure Power State changes to D0 happen *before* stream
>    format is set.
>  - Try to set the Power State to D0 on .prepare callback too as
>    recovery from suspend state doesn't need .hw_params call.
> 
> This patchset adds 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. The patch
> "ALSA: usb-audio: Operate UAC3 Power Domains in PCM callbacks"
> puts the logic for doing so inside the PCM's logic. Something to
> improve on that is to also tie up those D1<->D0 state changes
> to runtime PM maybe.
> 
> 
> Jorge Sanjuan (4):
>   ALSA: usb-audio: Initial Power Domain support
>   ALSA: usb-audio: AudioStreaming Power Domain parsing
>   ALSA: usb-audio: Add UAC3 Power Domains to suspend/resume
>   ALSA: usb-audio: Operate UAC3 Power Domains in PCM callbacks

Now I merge all these four patches.  Thanks!


Takashi