feat(freertos): Add config to move additional functions into Flash

This commit adds a new Kconfig option, viz.,
CONFIG_FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH, which places
additional FreeRTOS functions, such as those which can be called from
and ISR context, into Flash memory. This feature utilizes the Flash auto
suspend/resume feature of the Flash chip.

components/freertos/Kconfig

@@ -563,6 +563,15 @@ menu "FreeRTOS"
                 When enabled the selected Non-ISR FreeRTOS functions will be placed into Flash memory instead of IRAM.
                 This saves up to 8KB of IRAM depending on which functions are used.
 
+        config FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH
+            bool "Place FreeRTOS functions called from ISR context into Flash"
+            depends on SPI_FLASH_AUTO_SUSPEND && FREERTOS_PLACE_FUNCTIONS_INTO_FLASH
+            default n
+            help
+                When enabled additional FreeRTOS functions which maybe called from an ISR context are
+                also placed in Flash, thus freeing up more IRAM.
+                This option is only applicable when the SPI_FLASH_AUTO_SUSPEND feature is supported.
+
         config FREERTOS_CHECK_PORT_CRITICAL_COMPLIANCE
             # Todo: Check if we still need this (IDF-4986)
             bool "Tests compliance with Vanilla FreeRTOS port*_CRITICAL calls"
@@ -650,4 +659,9 @@ menu "FreeRTOS"
         default 1 if FREERTOS_UNICORE
         default 2 if !FREERTOS_UNICORE
 
+    config FREERTOS_IN_IRAM
+        # Invisible option enabled by default to place all freertos functions in internal RAM
+        # Todo: See linker.lf (IDF-12695)
+        bool
+        default y
 endmenu # FreeRTOS

components/freertos/linker.lf

@@ -7,12 +7,31 @@
 #   - CONFIG_FREERTOS_PLACE_FUNCTIONS_INTO_FLASH:
 #       - Place functions in flash if they are never called from an ISR context (directly or indirectly).
 #       - Some functions that are called often (such as critical sections) are placed in internal RAM for speed.
+#   - CONFIG_FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH:
+#       - Place additional functions such as the FromISR() variants in flash as well.
+#
+#   TODO: In IDF 6.0, evaluate the possibility of (IDF-12695):
+#       1. Default behavior: All FreeRTOS functions should be placed in flash by default, except for:
+#          - FromISR() functions
+#          - Performance-critical functions, such as critical section APIs and code related to context switching
+#       2. Deprecate the FREERTOS_PLACE_FUNCTIONS_INTO_FLASH Kconfig option and unhide the FREERTOS_IN_IRAM Kconfig
+#          option. Present FREERTOS_IN_IRAM config option to users as a performance optimization feature, with the
+#          trade-off of reduced internal RAM availability. This option would be disabled by default.
+#       3. FREERTOS_IN_IRAM config option should be user-configurable only if SPI_FLASH_AUTO_SUSPEND is supported.
+#          If not supported, it should be enabled by default and follow the placement rules stated above.
+#       4. If SPI_FLASH_AUTO_SUSPEND is supported, place additional FreeRTOS functions - including FromISR()
+#          variants, in Flash. Control this behavior using the FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH
+#          config option.
 # ----------------------------------------------------------------------------------------------------------------------
 
 [mapping:freertos_idf]
 archive: libfreertos.a
 entries:
-    * (noflash_text)        # Default all FreeRTOS functions to IRAM
+    if FREERTOS_IN_IRAM = y:
+        * (noflash_text)        # All FreeRTOS functions to IRAM
+    #else
+    # TODO: Enable in IDF 6.0
+    #    * (default)             # All FreeRTOS functions to Flash
     if FREERTOS_PLACE_FUNCTIONS_INTO_FLASH = y:
         # --------------------------------------------------------------------------------------------------------------
         # event_groups.c
@@ -25,26 +44,41 @@ entries:
         event_groups:xEventGroupClearBits (default)
         event_groups:xEventGroupSetBits (default)
         event_groups:vEventGroupDelete (default)
+        event_groups: xEventGroupGetStaticBuffer (default)
         event_groups:vEventGroupSetBitsCallback (default)
         event_groups:vEventGroupClearBitsCallback (default)
         event_groups:prvTestWaitCondition (default)
         if FREERTOS_USE_TRACE_FACILITY = y:
             event_groups: uxEventGroupGetNumber (default)
             event_groups: vEventGroupSetNumber (default)
+        if FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH = y:
+            event_groups: xEventGroupClearBitsFromISR (default)
+            event_groups: xEventGroupGetBitsFromISR (default)
+            event_groups: xEventGroupSetBitsFromISR (default)
         # --------------------------------------------------------------------------------------------------------------
         # list.c
         # - List/List Item initialization functions are never called from ISR
+        # - vListInsert is never called from an ISR context
+        # - Remaining List insertion/removal functions can be called from an ISR context and hence place them in flash
+        #   only when CONFIG_FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH is enabled
         # --------------------------------------------------------------------------------------------------------------
         list:vListInitialise (default)
         list:vListInitialiseItem (default)
+        list:vListInsert (default)
+        if FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH = y:
+            list:vListInsertEnd (default)
+            list:uxListRemove (default)
         # --------------------------------------------------------------------------------------------------------------
         # queue.c
         # - Keep all ...FromISR() functions (and their prv... calls) in internal RAM
         # - All other functions can be moved to flash
         # - Queue lock related functions are only used in single core builds
+        # - If CONFIG_FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH is enabled, place all FromISR() functions and their
+        #   dependents in flash as well
         # --------------------------------------------------------------------------------------------------------------
         queue:xQueueGenericReset (default)
         queue:xQueueGenericCreateStatic (default)
+        queue:xQueueGenericGetStaticBuffers (default)
         queue:xQueueGenericCreate (default)
         queue:prvInitialiseNewQueue (default)
         queue:prvInitialiseMutex (default)
@@ -80,14 +114,31 @@ entries:
         queue:xQueueAddToSet (default)
         queue:xQueueRemoveFromSet (default)
         queue:xQueueSelectFromSet (default)
+        if FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH = y:
+            queue:xQueueGetMutexHolderFromISR (default)
+            queue:xQueueGenericSendFromISR (default)
+            queue:prvCopyDataToQueue (default)
+            queue:prvNotifyQueueSetContainer (default)
+            queue:xQueueGiveFromISR (default)
+            queue:xQueueReceiveFromISR (default)
+            queue:prvCopyDataFromQueue (default)
+            queue:xQueuePeekFromISR (default)
+            queue:uxQueueMessagesWaitingFromISR (default)
+            queue:xQueueIsQueueEmptyFromISR (default)
+            queue:xQueueIsQueueFullFromISR (default)
+            queue:xQueueSelectFromSetFromISR (default)
         # --------------------------------------------------------------------------------------------------------------
         # stream_buffer.c
+        # - If CONFIG_FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH is enabled, place all FromISR() functions and their
+        #   dependents in flash as well
         # --------------------------------------------------------------------------------------------------------------
         stream_buffer:xStreamBufferGenericCreate (default)
         stream_buffer:xStreamBufferGenericCreateStatic (default)
+        stream_buffer:xStreamBufferGetStaticBuffers (default)
         stream_buffer:vStreamBufferDelete (default)
         stream_buffer:xStreamBufferReset (default)
         stream_buffer:xStreamBufferSetTriggerLevel (default)
+        stream_buffer:xStreamBufferSpacesAvailable (default)
         stream_buffer:xStreamBufferBytesAvailable (default)
         stream_buffer:xStreamBufferSend (default)
         stream_buffer:xStreamBufferReceive (default)
@@ -101,14 +152,31 @@ entries:
             stream_buffer:uxStreamBufferGetStreamBufferNumber (default)
             stream_buffer:vStreamBufferSetStreamBufferNumber (default)
             stream_buffer:ucStreamBufferGetStreamBufferType (default)
+        if FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH = y:
+            stream_buffer:xStreamBufferSendFromISR (default)
+            stream_buffer:prvWriteMessageToBuffer (default)
+            stream_buffer:xStreamBufferReceiveFromISR (default)
+            stream_buffer:prvReadMessageFromBuffer (default)
+            stream_buffer:xStreamBufferSendCompletedFromISR (default)
+            stream_buffer:xStreamBufferReceiveCompletedFromISR (default)
+            stream_buffer:prvBytesInBuffer (default)
         # --------------------------------------------------------------------------------------------------------------
         # tasks.c
-        # - Tickless idle functions (i.e., step tick) are left in internal RAM for speed
+        # - The following functions are always kept in internal RAM as they are frequently called during context switches
+        #   - xTaskIncrementTick
+        #   - prvSelectHighestPriorityTaskSMP
+        #   - vTaskSwitchContext
+        # - Tickless idle functions (i.e., step tick) are left in internal RAM for speed unless
+        #   CONFIG_FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH is enabled
+        # - Place all functions that are called from an ISR context into Flash if
+        #   CONFIG_FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH is enabled
         # - The following functions are called when the cache is disabled, thus they are excluded from the list below
         #   (i.e., called after "spi_flash_disable_interrupts_caches_and_other_cpu()" is called).
         #   - "xTaskGetSchedulerState"
         #   - "xTaskGetTickCount"
         # --------------------------------------------------------------------------------------------------------------
+        tasks:xTaskCreateRestrictedStatic (default)
+        tasks:xTaskCreateRestricted (default)
         tasks:prvInitialiseNewTask (default)
         tasks:prvAddNewTaskToReadyList (default)
         tasks:vTaskDelete (default)
@@ -119,22 +187,26 @@ entries:
         tasks:vTaskPrioritySet (default)
         tasks:vTaskSuspend (default)
         tasks:vTaskResume (default)
+        tasks:prvCreateIdleTasks (default)
         tasks:vTaskStartScheduler (default)
         tasks:vTaskEndScheduler (default)
         tasks:vTaskSuspendAll (default)
-        if CONFIG_FREERTOS_USE_TICKLESS_IDLE = y:
+        if FREERTOS_USE_TICKLESS_IDLE = y:
             tasks:prvGetExpectedIdleTime (default)
+            tasks:eTaskConfirmSleepModeStatus (default)
         tasks:xTaskResumeAll (default)
         tasks:uxTaskGetNumberOfTasks (default)
         tasks:pcTaskGetName (default)
         tasks:prvSearchForNameWithinSingleList (default)
         tasks:xTaskGetHandle (default)
+        tasks:xTaskGetStaticBuffers (default)
         tasks:xTaskGetIdleTaskHandle (default)
+        tasks:xTaskCatchUpTicks (default)
         tasks:xTaskAbortDelay (default)
-        # IDF-6410 Application tags not supported yet
-        #tasks:vTaskSetApplicationTaskTag (default)
-        #tasks:xTaskGetApplicationTaskTag (default)
-        #tasks:xTaskCallApplicationTaskHook (default)
+        if FREERTOS_USE_APPLICATION_TASK_TAG = y:
+            tasks:vTaskSetApplicationTaskTag (default)
+            tasks:xTaskGetApplicationTaskTag (default)
+            tasks:xTaskCallApplicationTaskHook (default)
         tasks:vTaskPlaceOnEventList (default)
         tasks:vTaskPlaceOnUnorderedEventList (default)
         tasks:vTaskPlaceOnEventListRestricted (default)
@@ -179,20 +251,36 @@ entries:
             tasks:vTaskSetTaskNumber (default)
             tasks:vTaskGetInfo (default)
             tasks:prvListTasksWithinSingleList (default)
+        if FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH = y:
+            tasks:prvIsYieldRequiredSMP (default)
+            tasks:prvCheckTaskCanBeScheduledSMP (default)
+            tasks:uxTaskPriorityGetFromISR (default)
+            tasks:prvTaskIsTaskSuspended (default)
+            tasks:xTaskResumeFromISR (default)
+            tasks:xTaskGetTickCountFromISR (default)
+            tasks:xTaskGetApplicationTaskTagFromISR (default)
+            tasks:xTaskRemoveFromEventList (default)
+            tasks:prvResetNextTaskUnblockTime (default)
+            tasks:xTaskGenericNotifyFromISR (default)
+            tasks:vTaskGenericNotifyGiveFromISR (default)
+            if FREERTOS_USE_TICKLESS_IDLE = y:
+                tasks:vTaskStepTick (default)
         # --------------------------------------------------------------------------------------------------------------
         # timers.c
         # - xTimerGenericCommand() is used for ISR calls as well. Thus leave it (and its dependents) in internal RAM
+        #   unless CONFIG_FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH is enabled
         # --------------------------------------------------------------------------------------------------------------
         timers:xTimerCreateTimerTask (default)
         timers:xTimerCreate (default)
         timers:xTimerCreateStatic (default)
         timers:prvInitialiseNewTimer (default)
-        timers:xTimerGenericCommand (default)
         timers:xTimerGetTimerDaemonTaskHandle (default)
         timers:xTimerGetPeriod (default)
         timers:vTimerSetReloadMode (default)
+        timers:xTimerGetReloadMode (default)
         timers:uxTimerGetReloadMode (default)
         timers:xTimerGetExpiryTime (default)
+        timers:xTimerGetStaticBuffer (default)
         timers:pcTimerGetName (default)
         timers:prvReloadTimer (default)
         timers:prvProcessExpiredTimer (default)
@@ -211,30 +299,78 @@ entries:
         if FREERTOS_USE_TRACE_FACILITY = y:
             timers:uxTimerGetTimerNumber (default)
             timers:vTimerSetTimerNumber (default)
+        if FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH = y:
+            timers:xTimerGenericCommand (default)
+            timers:xTimerPendFunctionCallFromISR (default)
         # --------------------------------------------------------------------------------------------------------------
         # portable/xtensa/port.c
-        # - Most functions are called from an ISR context, except for scheduler/task init/deinit functions
-        # - MPU/Coproc currently only exists on ESP32/S3
+        # - Most functions are called from an ISR context, except for scheduler/task init/deinit functions. Functions
+        #   called from ISR context are placed in flash only when CONFIG_FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH
+        #   is enabled
+        # - Critical sections functions are always placed in internal RAM for better performance
+        # - The following functions are also placed in internal RAM as they are called from vTaskSwitchContext, which is
+        #   also always placed in internal RAM
+        #   - vApplicationStackOverflowHook
+        #   - vPortSetStackWatchpoint
         # --------------------------------------------------------------------------------------------------------------
         if IDF_TARGET_ARCH_XTENSA = y:
             port:xPortStartScheduler (default)
             port:vPortEndScheduler (default)
+            if FREERTOS_TASK_FUNCTION_WRAPPER = y:
+                port:vPortTaskWrapper (default)
+            if SOC_CPU_COPROC_NUM > 0:
+                port:uxInitialiseStackCPSA (default)
+            port:uxInitialiseStackTLS (default)
+            port:uxInitialiseStackFrame (default)
             port:pxPortInitialiseStack (default)
             port:xPortGetTickRateHz (default)
             if FREERTOS_TLSP_DELETION_CALLBACKS = y:
                 port:vPortTLSPointersDelCb (default)
-            if IDF_TARGET_ESP32 = y || IDF_TARGET_ESP32S3 = y :
+            if SOC_CPU_COPROC_NUM > 0:
                 port:vPortCleanUpCoprocArea (default)
             port:vPortTCBPreDeleteHook (default)
+            if FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH = y:
+                port:xPortInIsrContext (default)
+                port:vPortAssertIfInISR (default)
+                port:xPortInterruptedFromISRContext (default)
+                port:vPortYieldOtherCore (default)
         # --------------------------------------------------------------------------------------------------------------
         # portable/riscv/port.c
-        # - Most functions are called from an ISR context, except for scheduler/task init/deinit functions
+        # - Most functions are called from an ISR context, except for scheduler/task init/deinit functions. Functions
+        #   called from ISR context are placed in flash only when CONFIG_FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH
+        #   is enabled
+        # - Critical sections functions are always placed in internal RAM for better performance
+        # - The following functions are also placed in internal RAM as they are called from vTaskSwitchContext, which is
+        #   also always placed in internal RAM
+        #   - vApplicationStackOverflowHook
+        #   - vPortSetStackWatchpoint
+        # - vPortCoprocUsedInISR is directly called from RISC-V assembly code with a direct branch instruction which
+        #   may be too far when placed in Flash. Hence, it is always placed in internal RAM
         # --------------------------------------------------------------------------------------------------------------
         if IDF_TARGET_ARCH_RISCV = y:
             port:xPortStartScheduler (default)
             port:vPortEndScheduler (default)
+            port:uxInitialiseStackTLS (default)
+            if FREERTOS_TASK_FUNCTION_WRAPPER = y:
+                port:vPortTaskWrapper (default)
+            if SOC_CPU_COPROC_NUM > 0:
+                port:pxRetrieveCoprocSaveAreaFromStackPointer (default)
+                port:uxInitialiseCoprocSaveArea (default)
+                port:vPortCleanUpCoprocArea (default)
+                port:pxPortGetCoprocArea (default)
+                port:pxPortUpdateCoprocOwner (default)
+                if FREERTOS_UNICORE = n:
+                    port:vPortTaskPinToCore (default)
+            port:uxInitialiseStackFrame (default)
             port:pxPortInitialiseStack (default)
+            port:vPortYield (default)
             port:xPortGetTickRateHz (default)
             if FREERTOS_TLSP_DELETION_CALLBACKS = y:
                 port:vPortTLSPointersDelCb (default)
             port:vPortTCBPreDeleteHook (default)
+            if FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH = y:
+                port:xPortInIsrContext (default)
+                port:vPortAssertIfInISR (default)
+                port:xPortInterruptedFromISRContext (default)
+                port:vPortYieldFromISR (default)
+                port:vPortYieldOtherCore (default)

components/freertos/linker_common.lf

@@ -10,11 +10,14 @@ entries:
     #   - Default: Place all functions in internal RAM.
     #   - CONFIG_FREERTOS_PLACE_FUNCTIONS_INTO_FLASH: Place functions in flash if they are never called from an ISR
     #     context (directly or indirectly).
+    #   - xTaskIncrementTickOtherCores is always placed in internal RAM for better performance
     # Placement Rules (Task Snapshot):
     #   - Default: Place all functions in internal RAM.
     #   - CONFIG_FREERTOS_PLACE_SNAPSHOT_FUNS_INTO_FLASH: Place functions in flash
     #   - vTaskGetSnapshot is omitted on purpose as it is used to by the Task Watchdog (TWDT) interrupt handler, we want
-    #     to always keep it in IRAM
+    #     to always keep it in IRAM unless CONFIG_FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH is enabled in which case
+    #     we can place it in flash.
+    #
     # ------------------------------------------------------------------------------------------------------------------
     if FREERTOS_PLACE_FUNCTIONS_INTO_FLASH = y:
         # Kernel Control
@@ -37,11 +40,21 @@ entries:
         # TLSP Deletion Callbacks
         if FREERTOS_TLSP_DELETION_CALLBACKS = y:
             tasks:vTaskSetThreadLocalStoragePointerAndDelCallback (default)
+        # Newlib re-entrancy
+        tasks:__getreent (default)
+        # Miscellaneous
+        tasks:pvTaskGetCurrentTCBForCore (default)
+        if SPIRAM = y:
+            # PSRAM
+            tasks:prvTaskCreateDynamicPinnedToCoreWithCaps (default)
     # Task Snapshot
     if FREERTOS_PLACE_SNAPSHOT_FUNS_INTO_FLASH = y:
         tasks:pxGetTaskListByIndex (default)
         tasks:xTaskGetNext (default)
         tasks:uxTaskGetSnapshotAll (default)
+        if FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH = y:
+            tasks:vTaskGetSnapshot (default)
+
 
     # ------------------------------------------------------------------------------------------------------------------
     # freertos_compatibility.c
@@ -55,6 +68,12 @@ entries:
     # ------------------------------------------------------------------------------------------------------------------
     idf_additions (default)
 
+    # ------------------------------------------------------------------------------------------------------------------
+    # idf_additions_event_groups.c
+    # Placement Rules: Functions always in flash as they are never called from an ISR
+    # ------------------------------------------------------------------------------------------------------------------
+    idf_additions_event_groups (default)
+
     # ------------------------------------------------------------------------------------------------------------------
     # app_startup.c
     # Placement Rules: Functions always in flash as they are never called from an ISR
@@ -74,6 +93,7 @@ entries:
         heap_idf:vPortFree (default)
         heap_idf:xPortGetFreeHeapSize (default)
         heap_idf:xPortGetMinimumEverFreeHeapSize (default)
+        heap_idf:xPortCheckValidListMem (default)
         if FREERTOS_SMP = n:
             heap_idf:xPortCheckValidTCBMem (default)
             heap_idf:xPortcheckValidStackMem (default)

components/freertos/test_apps/freertos/kernel/event_groups/test_freertos_eventgroups.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2022-2024 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2022-2025 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */

components/freertos/test_apps/freertos/pytest_freertos.py

@@ -56,6 +56,19 @@ def test_freertos(dut: Dut) -> None:
     dut.run_all_single_board_cases()
 
 
+@pytest.mark.generic
+@pytest.mark.flash_suspend
+@idf_parametrize(
+    'config,target',
+    [
+        ('flash_auto_suspend', 'esp32c3'),
+    ],
+    indirect=['config', 'target'],
+)
+def test_freertos_flash_auto_suspend(dut: Dut) -> None:
+    dut.run_all_single_board_cases()
+
+
 @pytest.mark.generic
 @pytest.mark.parametrize('config', ['freertos_options'], indirect=True)
 @idf_parametrize('target', ['supported_targets'], indirect=['target'])

components/freertos/test_apps/freertos/sdkconfig.ci.flash_auto_suspend

@@ -0,0 +1,7 @@
+# Enable Flash auto suspend/resume feature
+CONFIG_SPI_FLASH_AUTO_SUSPEND=y
+CONFIG_SPI_FLASH_FORCE_ENABLE_XMC_C_SUSPEND=y
+
+# Enable FreeRTOS in Flash feature
+CONFIG_FREERTOS_PLACE_FUNCTIONS_INTO_FLASH=y
+CONFIG_FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH=y

tools/test_apps/configs/sdkconfig.flash_auto_suspend_iram_reduction

@@ -9,6 +9,7 @@ CONFIG_COMPILER_OPTIMIZATION_SIZE=y
 
 #  Options that will enable IRAM reduction option that are not necessarily safe for all use-cases
 CONFIG_RINGBUF_PLACE_ISR_FUNCTIONS_INTO_FLASH=y
+CONFIG_FREERTOS_PLACE_ISR_FUNCTIONS_INTO_FLASH=y
 
 # Options that will enable IRAM reduction option that are only usable together with flash auto-suspend
 CONFIG_SPI_FLASH_AUTO_SUSPEND=y