arc: add dependences on MMU presence

Depending on MMU presence in CPU there're differences in HW behavior.
For example address of instruction that caused exception is put in
ECR register if MMU exists and in ERET register otherwise.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Signed-off-by: Igor Guryanov <guryanov@synopsys.com>

arch/arc/config.mk

@@ -21,6 +21,10 @@ ifeq ($(CROSS_COMPILE),)
 CROSS_COMPILE := $(ARC_CROSS_COMPILE)
 endif
 
+ifdef CONFIG_ARC_MMU_VER
+CONFIG_MMU = 1
+endif
+
 PLATFORM_CPPFLAGS += -ffixed-r25 -D__ARC__ -gdwarf-2
 
 # Needed for relocation

arch/arc/cpu/arc700/start.S

@@ -78,6 +78,16 @@
 	PUSHAX	%erbta
 .endm
 
+.macro SAVE_EXCEPTION_SOURCE
+#ifdef CONFIG_MMU
+	/* If MMU exists exception faulting address is loaded in EFA reg */
+	lr	%r0, [%efa]
+#else
+	/* Otherwise in ERET (exception return) reg */
+	lr	%r0, [%eret]
+#endif
+.endm
+
 .align 4
 .globl _start
 _start:
@@ -102,13 +112,13 @@ _start:
 
 memory_error:
 	SAVE_ALL_SYS
-	lr	%r0, [%efa]
+	SAVE_EXCEPTION_SOURCE
 	mov	%r1, %sp
 	j	do_memory_error
 
 instruction_error:
 	SAVE_ALL_SYS
-	lr	%r0, [%efa]
+	SAVE_EXCEPTION_SOURCE
 	mov	%r1, %sp
 	j	do_instruction_error
 
@@ -119,7 +129,7 @@ interrupt_handler:
 
 EV_MachineCheck:
 	SAVE_ALL_SYS
-	lr	%r0, [%efa]
+	SAVE_EXCEPTION_SOURCE
 	mov	%r1, %sp
 	j	do_machine_check_fault
 
@@ -135,7 +145,7 @@ EV_TLBMissD:
 
 EV_TLBProtV:
 	SAVE_ALL_SYS
-	lr	%r0, [%efa]
+	SAVE_EXCEPTION_SOURCE
 	mov	%r1, %sp
 	j	do_tlb_prot_violation