ARC: [intc-compact] simplify code for 2 priority levels

ARC700 support for 2 interrupt priorities historically allowed even slow
perpherals such as emac and uart to setup high priority interrupts
which was wrong from the beginning as they could possibly delay the more
critical timer interrupt.

The hardware support for 2 level interrupts in ARCompact is less than
ideal anyways (judging from the "hacks" in low level entry code and thus
is not used in productions systems I know of.

So reduce the scope of this to timer only, thereby reducing a bunch of
complexity.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/Kconfig

@@ -186,9 +186,6 @@ if SMP
 config ARC_HAS_COH_CACHES
 	def_bool n
 
-config ARC_HAS_REENTRANT_IRQ_LV2
-	def_bool n
-
 config ARC_MCIP
 	bool "ARConnect Multicore IP (MCIP) Support "
 	depends on ISA_ARCV2
@@ -366,25 +363,10 @@ config NODES_SHIFT
 if ISA_ARCOMPACT
 
 config ARC_COMPACT_IRQ_LEVELS
-	bool "ARCompact IRQ Priorities: High(2)/Low(1)"
+	bool "Setup Timer IRQ as high Priority"
 	default n
-	# Timer HAS to be high priority, for any other high priority config
-	select ARC_IRQ3_LV2
 	# if SMP, LV2 enabled ONLY if ARC implementation has LV2 re-entrancy
-	depends on !SMP || ARC_HAS_REENTRANT_IRQ_LV2
-
-if ARC_COMPACT_IRQ_LEVELS
-
-config ARC_IRQ3_LV2
-	bool
-
-config ARC_IRQ5_LV2
-	bool
-
-config ARC_IRQ6_LV2
-	bool
-
-endif	#ARC_COMPACT_IRQ_LEVELS
+	depends on !SMP
 
 config ARC_FPU_SAVE_RESTORE
 	bool "Enable FPU state persistence across context switch"

arch/arc/kernel/entry-compact.S

@@ -91,27 +91,13 @@ VECTOR   mem_service             ; 0x8, Mem exception   (0x1)
 VECTOR   instr_service           ; 0x10, Instrn Error   (0x2)
 
 ; ******************** Device ISRs **********************
-#ifdef CONFIG_ARC_IRQ3_LV2
-VECTOR   handle_interrupt_level2
-#else
-VECTOR   handle_interrupt_level1
-#endif
-
-VECTOR   handle_interrupt_level1
-
-#ifdef CONFIG_ARC_IRQ5_LV2
-VECTOR   handle_interrupt_level2
-#else
-VECTOR   handle_interrupt_level1
-#endif
-
-#ifdef CONFIG_ARC_IRQ6_LV2
+#ifdef CONFIG_ARC_COMPACT_IRQ_LEVELS
 VECTOR   handle_interrupt_level2
 #else
 VECTOR   handle_interrupt_level1
 #endif
 
-.rept   25
+.rept   28
 VECTOR   handle_interrupt_level1 ; Other devices
 .endr
 

arch/arc/kernel/intc-compact.c

@@ -28,10 +28,8 @@ void arc_init_IRQ(void)
 {
 	int level_mask = 0;
 
-       /* setup any high priority Interrupts (Level2 in ARCompact jargon) */
-	level_mask |= IS_ENABLED(CONFIG_ARC_IRQ3_LV2) << 3;
-	level_mask |= IS_ENABLED(CONFIG_ARC_IRQ5_LV2) << 5;
-	level_mask |= IS_ENABLED(CONFIG_ARC_IRQ6_LV2) << 6;
+       /* Is timer high priority Interrupt (Level2 in ARCompact jargon) */
+	level_mask |= IS_ENABLED(CONFIG_ARC_COMPACT_IRQ_LEVELS) << TIMER0_IRQ;
 
 	/*
 	 * Write to register, even if no LV2 IRQs configured to reset it