arch: split dynamic interrupt symbol

This commit introduces the SRAM_SW_ISR_TABLE option which is selected by
DYNAMIC_INTERRUPT. It allows splitting the DYNAMIC_INTERRUPT option into
two parts:

 - One for the relocation of the ISR vector table in RAM
 - One for the inclusion of functions needed to install ISRs dynamically

The goal is to later only select the relocation of the ISR vector table in
RAM and not all the associated functions from the dynamic interrupt
mechanism.

Signed-off-by: Martin Hoff <[email protected]>

Author: Martinhoff-maker

arch/Kconfig

@@ -472,6 +472,7 @@ config ISR_TABLES_LOCAL_DECLARATION
 
 config DYNAMIC_INTERRUPTS
 	bool "Installation of IRQs at runtime"
+	select SRAM_SW_ISR_TABLE
 	help
 	  Enable installation of interrupts at runtime, which will move some
 	  interrupt-related data structures to RAM instead of ROM, and
@@ -598,6 +599,12 @@ config SRAM_VECTOR_TABLE
 	  When XiP is enabled, this option will result in the vector table being
 	  relocated from Flash to SRAM.
 
+config SRAM_SW_ISR_TABLE
+	bool "Place the software ISR table in SRAM instead of flash"
+	help
+	  The option specifies that the software interrupts vector table will be
+	  placed inside SRAM instead of the flash.
+
 config IRQ_OFFLOAD_NESTED
 	bool "irq_offload() supports nested IRQs"
 	depends on IRQ_OFFLOAD

cmake/linker_script/common/common-ram.cmake

@@ -2,7 +2,7 @@
 # The contents of this file is based on include/zephyr/linker/common-ram.ld
 # Please keep in sync
 
-if(CONFIG_GEN_SW_ISR_TABLE AND CONFIG_DYNAMIC_INTERRUPTS)
+if(CONFIG_GEN_SW_ISR_TABLE AND CONFIG_SRAM_SW_ISR_TABLE)
   # ld align has been changed to subalign to provide identical behavior scatter vs. ld.
   zephyr_linker_section(NAME sw_isr_table
     GROUP DATA_REGION

cmake/linker_script/common/common-rom.cmake

@@ -13,7 +13,7 @@ zephyr_linker_section_obj_level(SECTION init LEVEL SMP)
 
 zephyr_iterable_section(NAME device NUMERIC KVMA RAM_REGION GROUP RODATA_REGION)
 
-if(CONFIG_GEN_SW_ISR_TABLE AND NOT CONFIG_DYNAMIC_INTERRUPTS)
+if(CONFIG_GEN_SW_ISR_TABLE AND NOT CONFIG_SRAM_SW_ISR_TABLE)
   # ld align has been changed to subalign to provide identical behavior scatter vs. ld.
   zephyr_linker_section(NAME sw_isr_table KVMA FLASH GROUP RODATA_REGION SUBALIGN ${CONFIG_ARCH_SW_ISR_TABLE_ALIGN} NOINPUT)
   zephyr_linker_section_configure(

doc/kernel/services/interrupts.rst

@@ -197,6 +197,10 @@ generate exceptions that need to be handled synchronously (e.g. kernel panic).
     The feature is currently implemented in the ARM Cortex-M architecture
     variant.
 
+.. tip::
+    To mitigate flash access latency, consider relocating ISRs and all related
+    symbols to RAM. This eliminates flash access delays.
+
 Offloading ISR Work
 ===================
 
@@ -374,6 +378,16 @@ Cortex-M architecture variant via the macro
 :c:macro:`ARM_IRQ_DIRECT_DYNAMIC_CONNECT`, which can be used to declare a direct
 and dynamic interrupt.
 
+RAM-based ISR Execution
+=======================
+
+For ultra-low latency, ISRs and vector tables can be relocated to RAM to eliminate
+flash access delays. :kconfig:option:`CONFIG_SRAM_VECTOR_TABLE` and
+:kconfig:option:`CONFIG_SRAM_SW_ISR_TABLE` will help you have interrupt vectors
+in RAM. :kconfig:option:`CONFIG_DEVICE_MUTABLE` will help you put the device
+structure in RAM and :kconfig:option:`CONFIG_CODE_DATA_RELOCATION` will help you relocate
+the ISR and all the related symbols to RAM.
+
 Sharing an interrupt line
 =========================
 

doc/releases/release-notes-4.3.rst

@@ -75,6 +75,10 @@ New APIs and options
 
 .. zephyr-keep-sorted-start re(^\* \w)
 
+* Architectures
+
+  * :kconfig:option:`CONFIG_SRAM_SW_ISR_TABLE`
+
 * Power management
 
    * :c:func:`pm_device_driver_deinit`

include/zephyr/linker/common-ram.ld

@@ -17,7 +17,7 @@
 ITERABLE_SECTION_RAM(scmi_protocol, Z_LINK_ITERABLE_SUBALIGN)
 #endif /* CONFIG_ARM_SCMI */
 
-#if defined(CONFIG_GEN_SW_ISR_TABLE) && defined(CONFIG_DYNAMIC_INTERRUPTS)
+#if defined(CONFIG_GEN_SW_ISR_TABLE) && defined(CONFIG_SRAM_SW_ISR_TABLE)
 	SECTION_DATA_PROLOGUE(sw_isr_table,,)
 	{
 		/*

include/zephyr/linker/common-rom/common-rom-kernel-devices.ld

@@ -42,7 +42,7 @@
 	} GROUP_ROM_LINK_IN(RAMABLE_REGION, ROMABLE_REGION)
 #endif
 
-#if defined(CONFIG_GEN_SW_ISR_TABLE) && !defined(CONFIG_DYNAMIC_INTERRUPTS)
+#if defined(CONFIG_GEN_SW_ISR_TABLE) && !defined(CONFIG_SRAM_SW_ISR_TABLE)
 	SECTION_PROLOGUE(sw_isr_table,,)
 	{
 		/*