arch: arm: cortex_m: Allow VTOR to be relocated to DTCM

Relocate VTOR from SRAM to DTCM to minimize interrupt latency.
DTCM offers single-cycle access compared to multi-cycle SRAM reads.
This improves exception handling speed for real-time workloads.

Signed-off-by: Peter van der Perk <[email protected]>

Author: PetervdPerk-NXP

arch/Kconfig

@@ -621,6 +621,26 @@ config SRAM_VECTOR_TABLE
 	  When XiP is enabled, this option will result in the vector table being
 	  relocated from Flash to SRAM.
 
+DT_CHOSEN_Z_DTCM := zephyr,dtcm
+
+choice
+	prompt "Vector table memory location"
+	depends on SRAM_VECTOR_TABLE
+	default VECTOR_TABLE_SRAM
+
+config VECTOR_TABLE_SRAM
+	bool "SRAM"
+	help
+	  Place the vector table in SRAM.
+
+config VECTOR_TABLE_DTCM
+	bool "DTCM"
+	depends on $(dt_chosen_enabled,$(DT_CHOSEN_Z_DTCM))
+	help
+	  Place the vector table in DTCM if available.
+
+endchoice
+
 config SRAM_SW_ISR_TABLE
 	bool "Place the software ISR table in SRAM instead of flash"
 	help

arch/arm/core/cortex_m/ram_vector_table.ld

@@ -28,5 +28,9 @@ SECTION_PROLOGUE(.sram_vt,,)
 	. += _vector_end - _vector_start;
 	MPU_ALIGN(_sram_vector_size);
 	_sram_vector_end = .;
+#if defined(CONFIG_VECTOR_TABLE_DTCM)
+} GROUP_DATA_LINK_IN(DTCM, ROMABLE_REGION)
+#else
 } GROUP_DATA_LINK_IN(RAMABLE_REGION, ROMABLE_REGION)
+#endif
 _sram_vector_size = _sram_vector_end - _sram_vector_start;