Phase 2 (part 6): move arch and platform to src/kernel, build src/kernel into sof_kernel

AGENTS.md

@@ -31,7 +31,7 @@ moving code, follow it:
 
 * **Place code in the right tier.** OS/HAL/boot/inter-core → a kernel-only directory
   (`kernel/`, which is built into the `sof_kernel` library, and the directories not yet
-  moved there: `arch/`, `platform/`, `trace/`); audio
+  moved there: `trace/`); audio
   application logic → `audio/`; reusable pure code → a shared-library directory (`lib/`,
   `math/`, `module/`) kept free of privileged operations. Each top-level directory's
   `README.md` states its tier in a "Runs in:" banner — keep it accurate.

CMakeLists.txt

@@ -144,6 +144,6 @@ endif()
 
 if(BUILD_UNIT_TESTS)
 	enable_testing()
-	add_subdirectory(src/arch/${ARCH})
+	add_subdirectory(src/kernel/arch/${ARCH})
 	add_subdirectory(test)
 endif()

CODEOWNERS

@@ -47,9 +47,9 @@ src/audio/module_adapter/*		@ranj063 @jxstelter
 src/audio/google/*			@thesofproject/google
 
 # platforms
-src/platform/imx8/**			@dbaluta
-src/platform/amd/**			@bhiregoudar @sunilkumardommati
-src/platform/mtk/**			@yaochunhung @kuanhsuncheng
+src/kernel/platform/imx8/**			@dbaluta
+src/kernel/platform/amd/**			@bhiregoudar @sunilkumardommati
+src/kernel/platform/mtk/**			@yaochunhung @kuanhsuncheng
 
 # drivers
 src/drivers/intel/dmic.c		@singalsu

app/CMakeLists.txt

@@ -27,6 +27,6 @@ target_sources(app PRIVATE
   )
 
 zephyr_library_include_directories(app PUBLIC
-    ${CMAKE_CURRENT_SOURCE_DIR}/../src/arch/xtensa/include
+    ${CMAKE_CURRENT_SOURCE_DIR}/../src/kernel/arch/xtensa/include
     ${CMAKE_CURRENT_SOURCE_DIR}/../src/include
   )

scripts/cmake/defconfigs.cmake

@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: BSD-3-Clause
 
 # Looks for defconfig files in arch directories where kconfig.cmake looks too.
-set(DEFCONFIGS_DIRECTORY "${PROJECT_SOURCE_DIR}/src/arch/${ARCH}/configs")
+set(DEFCONFIGS_DIRECTORY "${PROJECT_SOURCE_DIR}/src/kernel/arch/${ARCH}/configs")
 file(GLOB DEFCONFIG_PATHS "${DEFCONFIGS_DIRECTORY}/*_defconfig")
 
 # Adds dependency on defconfigs directory

scripts/cmake/kconfig.cmake

@@ -13,14 +13,14 @@ if(NOT INIT_CONFIG_found)
 set(INIT_CONFIG "initial.config" CACHE STRING "Initial .config file")
 
 # - ".' is the top source directory.
-# - "src/arch/host/configs" holds the library (testbench) configurations
+# - "src/kernel/arch/host/configs" holds the library (testbench) configurations
 #   and is also used by defconfigs.cmake.
 # - "test/cmocka/configs" holds the unit test configurations.
 # - First found wins.
 # - If two directories ever use the same defconfig name then a full
 #   path must be used, e.g.: -DINIT_CONFIG=test/cmocka/configs/collision_defconfig
 
-set(init_config_search_list "." "src/arch/host/configs" "test/cmocka/configs")
+set(init_config_search_list "." "src/kernel/arch/host/configs" "test/cmocka/configs")
 
 find_file(INIT_CONFIG_found
 	NAMES ${INIT_CONFIG}
@@ -46,7 +46,7 @@ message(FATAL_ERROR
 	"Initial configuration missing, no ${INIT_CONFIG} found. "
 	"Provide a ${PROJECT_SOURCE_DIR}/initial.config file or specify some "
 	"other -DINIT_CONFIG=location relative to '${PROJECT_SOURCE_DIR}/' or "
-	"'${PROJECT_SOURCE_DIR}/src/arch/*/configs/'"
+	"'${PROJECT_SOURCE_DIR}/src/kernel/arch/*/configs/'"
 )
 endif()
 

scripts/kernel_user_partition.txt

@@ -46,7 +46,7 @@ src/include/sof/lib/cpu-clk-manager.h
 src/include/sof/lib/mailbox.h
 src/include/sof/lib/perf_cnt.h
 src/include/sof/lib/watchdog.h
-src/platform/*
+src/kernel/platform/*
 zephyr/include/rtos/clk.h
 zephyr/include/rtos/idc.h
 zephyr/include/rtos/interrupt.h

scripts/rebuild-testbench.sh

@@ -116,7 +116,7 @@ For temporary, interactive Kconfiguration use:
 
    $BUILD_BACKEND -C $TESTBENCH_DIR/$BUILD_DIR_NAME/sof_ep/build/  menuconfig
 
-Permanent configuration is "src/arch/host/configs/library_defconfig".
+Permanent configuration is "src/kernel/arch/host/configs/library_defconfig".
 
 For instant, incremental build:
 

src/CMakeLists.txt

@@ -1,7 +1,5 @@
 # SPDX-License-Identifier: BSD-3-Clause
 
-add_subdirectory(platform)
-add_subdirectory(arch)
 add_subdirectory(ipc)
 add_subdirectory(audio)
 add_subdirectory(lib)

src/Kconfig

@@ -1,8 +1,8 @@
 # SPDX-License-Identifier: BSD-3-Clause
 
-rsource "arch/Kconfig"
+rsource "kernel/arch/Kconfig"
 
-rsource "platform/Kconfig"
+rsource "kernel/platform/Kconfig"
 
 rsource "audio/Kconfig"
 

src/audio/README.md

@@ -15,5 +15,5 @@ modules in user context.
 
 When adding a component here, keep it inside the application tier: allocate through the module
 allocation syscalls (`mod_*`), mark any globals shared with the kernel using the partition
-markers, and never call kernel-only subsystems (`kernel/drivers/`, `platform/`, `kernel/idc/`)
+markers, and never call kernel-only subsystems (`kernel/drivers/`, `kernel/platform/`, `kernel/idc/`)
 directly.

src/include/sof/userspace/README.md

@@ -74,7 +74,7 @@ its subdirectories span all tiers.
 
 | Tier | Meaning | Directories |
 |------|---------|-------------|
-| **Kernel-only** | OS integration, HAL, boot, inter-core. Never executes in a user thread. Must not be reached directly from user code — only via a syscall. | `kernel/` (see [its README](../../../kernel/README.md)), `arch/`, `platform/`, `trace/` * |
+| **Kernel-only** | OS integration, HAL, boot, inter-core. Never executes in a user thread. Must not be reached directly from user code — only via a syscall. | `kernel/` (see [its README](../../../kernel/README.md)), `trace/` * |
 | **Boundary / bridge** | Owns the syscalls and the thread / memory-domain setup. Split internally: some translation units run kernel-side, some user-side (e.g. `handler-kernel.c` vs `handler-user.c`). | `schedule/`, `ipc/`, `debug/debug_stream/` *, and (in the Zephyr integration tree) `zephyr/syscall/` |
 | **Application** | Audio pipeline / component logic that runs in user threads under userspace configs. | `audio/` |
 | **Shared library** | Context-agnostic code linked into whichever context calls it. Must stay "user-safe": no privileged operations (no direct MMIO, no spinlocks held across syscalls, no raw kernel object access) so it is safe when pulled into a user build. | `math/`, `module/` |

src/ipc/README.md

@@ -45,7 +45,7 @@ graph TD
 
 ## Processing Flow
 
-When the host writes a command to the IPC mailbox and triggers an interrupt, the hardware-specific driver (`src/platform/...`) catches the IRQ and eventually calls down into the IPC framework.
+When the host writes a command to the IPC mailbox and triggers an interrupt, the hardware-specific driver (`src/kernel/platform/...`) catches the IRQ and eventually calls down into the IPC framework.
 
 Different RTOS environments (Zephyr vs. bare metal SOF native) handle the thread handoff differently. In Zephyr, this leverages the `k_work` queues heavily for `ipc_work_handler`.
 

src/kernel/CMakeLists.txt

@@ -21,6 +21,10 @@ if(zephyr)
 	add_subdirectory(logging)
 	add_subdirectory(probe)
 	add_subdirectory(schedule)
+else()
+	# Only built for the host
+	add_subdirectory(arch)
+	add_subdirectory(platform)
 endif()
 
 # Built for Zephyr and for the host

src/arch/README.md → src/kernel/arch/README.md

@@ -1,8 +1,8 @@
-# Architecture Support (`src/arch`)
+# Architecture Support (`src/kernel/arch`)
 
 > **Runs in:** Kernel-only — CPU-architecture primitives (Xtensa) execute in supervisor context
 > and are never linked into a user thread. See
-> [User/kernel split](../include/sof/userspace/README.md).
+> [User/kernel split](../../include/sof/userspace/README.md).
 
 This directory contains architecture-specific code. It sits below the RTOS and audio
 application and has no user-space entry points.

src/arch/host/CMakeLists.txt → src/kernel/arch/host/CMakeLists.txt

@@ -1,8 +1,8 @@
 # SPDX-License-Identifier: BSD-3-Clause
 
 # includes
-target_include_directories(sof_public_headers INTERFACE ${PROJECT_SOURCE_DIR}/src/arch/host/include)
-target_include_directories(sof_public_headers INTERFACE ${PROJECT_SOURCE_DIR}/src/platform/library/include)
+target_include_directories(sof_public_headers INTERFACE ${PROJECT_SOURCE_DIR}/src/kernel/arch/host/include)
+target_include_directories(sof_public_headers INTERFACE ${PROJECT_SOURCE_DIR}/src/kernel/platform/library/include)
 include(CheckCCompilerFlag)
 
 if (NOT CONFIG_SOF_ZEPHYR_STRICT_HEADERS)

src/platform/README.md → src/kernel/platform/README.md

@@ -1,8 +1,8 @@
-# Platform Support (`src/platform`)
+# Platform Support (`src/kernel/platform`)
 
 > **Runs in:** Kernel-only — platform bring-up, memory maps, interrupt wiring and IPC mailbox
 > windows are supervisor-context concerns and never run in a user thread. See
-> [User/kernel split](../include/sof/userspace/README.md).
+> [User/kernel split](../../include/sof/userspace/README.md).
 
 This directory contains SoC/platform-specific integration (e.g. Intel ACE, MediaTek, i.MX),
 including the Kconfig that selects the build target such as `PANTHERLAKE` (PTL). It configures

src/platform/mtk/tools/build.sh → src/kernel/platform/mtk/tools/build.sh

@@ -9,15 +9,15 @@ if [ -z "$PLATFORMS" ]; then
     PLATFORMS="mt8195 mt8188 mt8186"
 fi
 
-SOF=`cd ../../../..; /bin/pwd`
+SOF=`cd ../../../../..; /bin/pwd`
 
 for p in $PLATFORMS; do
 
-    SRCS="$SOF/src/platform/$p/lib/dai.c $SOF/src/platform/$p/afe-platform.c"
+    SRCS="$SOF/src/kernel/platform/$p/lib/dai.c $SOF/src/kernel/platform/$p/afe-platform.c"
 
-    INCS="-I$SOF/src/include -I$SOF/src/platform/posix/include -I$SOF/posix/include"
-    INCS="$INCS -I$SOF/src/arch/host/include -I$SOF/src/platform/$p/include/platform"
-    INCS="$INCS -I$SOF/src/platform/$p/include"
+    INCS="-I$SOF/src/include -I$SOF/src/kernel/platform/posix/include -I$SOF/posix/include"
+    INCS="$INCS -I$SOF/src/kernel/arch/host/include -I$SOF/src/kernel/platform/$p/include/platform"
+    INCS="$INCS -I$SOF/src/kernel/platform/$p/include"
 
     DEFS="-DRELATIVE_FILE=\"mt-dai-gen.c\" -DCONFIG_CORE_COUNT=1 -DCONFIG_IPC_MAJOR_3=1"