arch: arc: Add FIRQ option

Add FIRQ option and change the _isr_wrapper. Currently, firq is
enabled by default, but in some arc configuration, firq can be
disabled.

Signed-off-by: Wayne Ren <wei.ren@synopsys.com>

arch/arc/Kconfig

@@ -89,6 +89,17 @@ config	RGF_NUM_BANKS
 	register bank, the fast interrupt handler must save
 	and restore general purpose registers.
 
+config ARC_FIRQ
+	bool
+	prompt "FIRQ enable"
+	default y
+	help
+	Fast interrupts are supported (FIRQ). If FIRQ enabled, for interrupts
+	with highest priority, status32 and pc will be saved in aux regs,
+	other regs will be saved according to the number of register bank;
+	If FIRQ is disabled, the handle of interrupts with highest priority
+	will be same with other interrupts.
+
 config	ARC_STACK_CHECKING
 	bool
 	default y if HW_STACK_PROTECTION

arch/arc/core/CMakeLists.txt

@@ -2,7 +2,6 @@ zephyr_sources(
 	thread.c
 	thread_entry_wrapper.S
 	cpu_idle.S
-	fast_irq.S
 	fatal.c
 	fault.c
 	fault_s.S
@@ -18,6 +17,8 @@ zephyr_sources(
 	vector_table.c
 	)
 
+zephyr_sources_ifdef(CONFIG_ARC_FIRQ fast_irq.S)
+
 zephyr_sources_if_kconfig(irq_offload.c)
 zephyr_sources_ifdef(CONFIG_ATOMIC_OPERATIONS_CUSTOM atomic.c)
 add_subdirectory_ifdef(CONFIG_CPU_HAS_MPU mpu)

arch/arc/core/isr_wrapper.S

@@ -229,6 +229,7 @@ From RIRQ:
  */
 
 SECTION_FUNC(TEXT, _isr_wrapper)
+#if CONFIG_ARC_FIRQ
 #if CONFIG_RGF_NUM_BANKS == 1
 	st r0,[saved_r0]
 #endif
@@ -286,6 +287,11 @@ rirq_path:
 	mov.nz r2, _rirq_enter
 	j_s [r2]
 #endif
+#else
+	mov r3, _rirq_exit
+	mov r2, _rirq_enter
+	j_s [r2]
+#endif
 
 #ifdef CONFIG_KERNEL_EVENT_LOGGER_SLEEP
 GTEXT(_sys_k_event_logger_exit_sleep)