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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