Re: [PATCH v35 00/31] Introduce QC USB SND audio offloading support

[Stephan Gerhold <stephan.gerhold@linaro.org>]

On Tue, Feb 18, 2025 at 04:47:23PM -0800, Wesley Cheng wrote:
> Requesting to see if we can get some Acked-By tags, and merge on usb-next.
> 
> Several Qualcomm based chipsets can support USB audio offloading to a
> dedicated audio DSP, which can take over issuing transfers to the USB
> host controller.  The intention is to reduce the load on the main
> processors in the SoC, and allow them to be placed into lower power modes.
> There are several parts to this design:
>   1. Adding ASoC binding layer
>   2. Create a USB backend for Q6DSP
>   3. Introduce XHCI interrupter support
>   4. Create vendor ops for the USB SND driver
> 
>       USB                          |            ASoC
> --------------------------------------------------------------------
>                                    |  _________________________
>                                    | |sm8250 platform card     |
>                                    | |_________________________|
>                                    |         |           |
>                                    |      ___V____   ____V____
>                                    |     |Q6USB   | |Q6AFE    |  
>                                    |     |"codec" | |"cpu"    |
>                                    |     |________| |_________|
>                                    |         ^  ^        ^
>                                    |         |  |________|
>                                    |      ___V____    |
>                                    |     |SOC-USB |   |
>    ________       ________               |        |   |
>   |USB SND |<--->|QC offld|<------------>|________|   |
>   |(card.c)|     |        |<----------                |
>   |________|     |________|___     | |                |
>       ^               ^       |    | |    ____________V_________
>       |               |       |    | |   |APR/GLINK             |
>    __ V_______________V_____  |    | |   |______________________|
>   |USB SND (endpoint.c)     | |    | |              ^
>   |_________________________| |    | |              |
>               ^               |    | |   ___________V___________
>               |               |    | |->|audio DSP              |
>    ___________V_____________  |    |    |_______________________|
>   |XHCI HCD                 |<-    |
>   |_________________________|      |
> 

As I noted on v34 [1], this version is still missing instructions and
changes needed for testing this series. The device tree changes don't
need to be part of the same series, but there should be at least a link
provided to give other people the chance to provide Tested-by tags.

IMO we shouldn't merge this series without those instructions, otherwise
we risk that this just ends up being dead code that no one can use.

Can you please share the device tree changes for a board upstream and
any other changes needed to be able to test this series? E.g. for
sm8250-mtp.dts, based on the examples in your cover letter.

Thanks,
Stephan

[1]: https://lore.kernel.org/linux-arm-msm/Z63B_UE61OdrgEJY@linaro.org/