userspace: dp: Add option for executing userspace module IPC in DP thread

[softwarecki]

Add the SOF_USERSPACE_MOD_IPC_BY_DP_THREAD Kconfig option and implement support for executing userspace module IPC in its DP thread instead of the shared user worker thread.

[Copilot]

Pull request overview

Adds a Zephyr Kconfig option to route userspace module IPC handling through each module’s DP thread (instead of the shared userspace worker), and wires DP-thread event/work-item plumbing through the DP scheduler and userspace proxy layers.

Changes:

• Add SOF_USERSPACE_MOD_IPC_BY_DP_THREAD Kconfig option.
• Extend DP scheduler thread/event handling to wake on IPC events and run the userspace proxy IPC handler in the DP thread.
• Update userspace proxy to optionally signal/await IPC via the DP thread’s k_event, plus adjust system-agent startup timing for this mode.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
zephyr/Kconfig	Adds the new configuration option controlling IPC execution context.
src/schedule/zephyr_dp_schedule_thread.c	Handles IPC events in DP thread and registers per-module IPC handler/event linkage.
src/schedule/zephyr_dp_schedule.h	Adds per-task storage for the IPC work item pointer.
src/include/sof/audio/module_adapter/library/userspace_proxy.h	Extends userspace context with DP-thread event pointer and declares IPC handler registration API.
src/audio/module_adapter/module_adapter.c	Adjusts DP task/free sequencing around userspace application teardown.
src/audio/module_adapter/module/generic.c	Tweaks DP task cancellation behavior under the new IPC-by-DP-thread mode.
src/audio/module_adapter/library/userspace_proxy.c	Implements DP-thread IPC signaling path, IPC handler registration, and defers agent startup in this mode.

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[lgirdwood]

@softwarecki are you able to respond to copilot, e.g. some comments may be valid around deref of pointers, best to check and resolve.
Btw, can any of this be tested in a ztest today ?

[softwarecki]

@lgirdwood: I did not think about a ztest yet. I tested it by enabling the config option. I added it in the userspace overlay.