[FEATURE] remove XTOS support from SOF mainline

[kv2019i]

Is your feature request related to a problem? Please describe.
Since 2022, SOF has been moving to Zephyr as its primary RTOS with work tracked in #5794
Most SOF users have either completed the transition to Zephyr, or are in progress of adding support for Zephyr for their platforms.

This ticket is for removal of XTOS support from SOF main, leaving XTOS support only supported in release stable branches. There is a set of cleanups we can proceed with, once XTOS support is removed, so having a ticket to mark as a dependency is useful for tracking.

Describe the solution you'd like
XTOS support removal from "main" branch

Feature Breakdown
This feature cannot be performed as a single large PR as we have many platforms, drivers, features and abstractions based around the legacy xtos code and this means we will need to remove section by section and make any necessary adaptations as needed for each removal.

These lists are not exhaustive, but the starting point for xtos removal.

Xtos Platform removals

• Intel - platform headers and some platform drivers remain for Intel platforms.
• NXP - platform headers and some drivers remain for NXP platforms.
• AMD - platform headers and some drivers remain for AMD platforms.
• MTK - platform headers and some drivers remain for MTK platforms.

Xtos Peripheral Driver removals

• Intel - DMA drivers remain for Intel platforms.
• NXP - DMA, SAI, IPC drivers remain for NXP platforms.
• AMD - DAI, DMA, interrupt drivers remain for AMD platforms.
• MTK - DAI, DMA, interrupt drivers remain for MTK platforms.

Xtos Feature/abstraction removals

• DMA interface.
• Clock API
• IPC API.
• coherent API.
• wait API
• C library duplications.
• trace API

[kv2019i]

@lgirdwood opened discussion at https://github.com/orgs/thesofproject/discussions/9993

[lgirdwood]

@thesofproject/amd @thesofproject/nxp @thesofproject/intel @thesofproject/google @thesofproject/mediatek pls comment/review and provide any feedback.

[bhiregoudar]

@thesofproject/amd @thesofproject/nxp @thesofproject/intel @thesofproject/google @thesofproject/mediatek pls comment/review and provide any feedback.
@lgirdwood : We are in transition to Zephyr. DMA scheduling is removed in Zephyr and we have an issue with timer scheduler working, So, till we resolve timer based scheduler issue we need to support XTOS on AMD platforms.

[lgirdwood]

@thesofproject/amd @thesofproject/nxp @thesofproject/intel @thesofproject/google @thesofproject/mediatek pls comment/review and provide any feedback.
@lgirdwood : We are in transition to Zephyr. DMA scheduling is removed in Zephyr and we have an issue with timer scheduler working, So, till we resolve timer based scheduler issue we need to support XTOS on AMD platforms.

@bhiregoudar ok, do you have a schedule for fixing timer scheduling on AMD ?

Fwiw, we found DMA based scheduling would not scale beyond a few streams as stream start ordering meant DMA IRQs would fire in different sequences/times and could cause a lot of thrash and glitches...

Timer based scheduling works best when the DSP is clock master for the codecs (otherwise you need to add the ASRC), as all pipelines are executed from a single synchronous tick in a deterministic order. Feel free to create an issue and it should gather comments from others who have transitioned to timers for debug.

[iuliana-prodan]

@thesofproject/amd @thesofproject/nxp @thesofproject/intel @thesofproject/google @thesofproject/mediatek pls comment/review and provide any feedback.

From NXP's point of view, we have all platforms supported with Zephyr and timer domain.
We can remove the XTOS.

@dbaluta @LaurentiuM1234 do you see any issues with this?

[dbaluta]

@iuliana-prodan all good from my point of view.

[lgirdwood]

@andrew-mtk pls reply with any comments for Mediatek team. @andyross feedback welcome too.

[LaurentiuM1234]

IMO all good from NXP's side. Although @lgirdwood already mentioned this I want to stress out the fact that all IMX platforms are still using the XTOS IPC driver so we need to watch out for that.

[lgirdwood]

IMO all good from NXP's side. Although @lgirdwood already mentioned this I want to stress out the fact that all IMX platforms are still using the XTOS IPC driver so we need to watch out for that.

Yeah - that's something that @kv2019i is working on with Zephyr folks. We also need Zephyr clock driver too. We would need to keep the legacy drivers until Zephyr replacements were upstream.

[kv2019i]

IMO all good from NXP's side. Although @lgirdwood already mentioned this I want to stress out the fact that all IMX platforms are still using the XTOS IPC driver so we need to watch out for that.

Yeah - that's something that @kv2019i is working on with Zephyr folks. We also need Zephyr clock driver too. We would need to keep the legacy drivers until Zephyr replacements were upstream.

• IPC work tracked in [FEATURE][Zephyr] replace mailbox.h with a IPC abstraction #9697
• Clock work tracked in [FEATURE][Zephyr] implement clk.h with native Zephyr interface and drop platform clk.h #9541 (only Intel uses the more complex clock change interface, so this should be less of a blocker as there's no XTOS user left anyways)