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

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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



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