Re: [PATCH 1/1] ASoC: soc-dai: export some symbols

From: Mark Brown <broonie@kernel.org>
To: Jason Zhu <jason.zhu@rock-chips.com>
Cc: sugar.zhang@rock-chips.com, alsa-devel@alsa-project.org,
	tiwai@suse.com, lgirdwood@gmail.com
Subject: Re: [PATCH 1/1] ASoC: soc-dai: export some symbols
Date: Fri, 23 Sep 2022 13:55:52 +0100	[thread overview]
Message-ID: <Yy2s2PA/C1ngeb//@sirena.org.uk> (raw)
In-Reply-To: <dfeac54a-a264-835a-f155-90eb8f093314@rock-chips.com>

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On Wed, Sep 21, 2022 at 10:37:06AM +0800, Jason Zhu wrote:
> 在 2022/9/20 20:47, Mark Brown 写道:
> > On Tue, Sep 20, 2022 at 11:45:45AM +0800, Jason Zhu wrote:

> > > Sometimes we need to make some dais alive when close the card, like
> > > VAD, so these functions must be exported so that they can be called.

> > I'm not sure I fully understand the use case here - why wouldn't
> > the core know about the audio stream being kept active?  For
> > something like VAD I'd expect this to be just working like a
> > normal audio path, if there's a DSP consuming the audio stream
> > then it'll keep everything open.  If there is a good use case I
> > suspect it'll be clearer if you send the users along with this
> > patch.

> Thanks. For example, we use the VAD(Voice Activity Detect) & PDM(
> Pulse Density Modulation) to record sound>. The PDM is used to
> record and copy data to DDR memory by DMA when the system is alive.
> The VAD is used to detect voice from PDM and copy data to sram
> (The sram is small) when the system is sleep. If the VAD detect
> specific sound, wake up the system and continue to record sound.
> The data can not be lost in this process. So we attach VAD & PDM
> in the same card, then close the card and wake up VAD & PDM again
> when the system is goto sleep. Like these code:

This sounds like a very normal thing with a standard audio stream -
other devices have similar VAD stuff without needing to open code access
to the PCM operations?

> When the system is waked up, open the sound card. The data in sram
> is copied firstly and close the vad. Then use the DMA to move data
> to DDR memory from PDM.

Generally things just continue to stream the voice data through the same
VAD stream IIRC - switching just adds complexity here, you don't have to
deal with joining the VAD and regular streams up for one thing.

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