Re: [RFC PATCH 09/14] sound: usb: Introduce QC USB SND offloading support

[Wesley Cheng]

Hi Pierre,

On 1/4/2023 3:51 PM, Pierre-Louis Bossart wrote:
> On 12/23/22 17:31, Wesley Cheng wrote:
> > Several Qualcomm SoCs have a dedicated audio DSP, which has the ability to
> > support USB sound devices.  This vendor driver will implement the required
> > handshaking with the DSP, in order to pass along required resources that
> > will be utilized by the DSP's USB SW.  The communication channel used for
> > this handshaking will be using the QMI protocol.  Required resources
> > include:
> > - Allocated secondary event ring address
> > - EP transfer ring address
> > - Interrupter number
> >
> > The above information will allow for the audio DSP to execute USB transfers
> > over the USB bus.  It will also be able to support devices that have an
> > implicit feedback and sync endpoint as well.  Offloading these data
> > transfers will allow the main/applications processor to enter lower CPU
> > power modes, and sustain a longer duration in those modes.
>
> Are you suggesting that the entire feedback loop be handled in the DSP?
> It's not clear what "Offloading these data transfers" refers to, the
> data part or the feedback path?

Yes, as mentioned in the cover letter response, we'll handle the 
feedback endpoints. (feedback eps are part of the audio data interface)

> Comments are almost inexistent in this patch so it's hard to figure out
> what it really does.

OK, will add some more comments.

Thanks
Wesley Cheng