ARC: [mm] Remove @write argument to do_page_fault()

This can be ascertained within do_page_fault() since it gets the full
ECR (Exception Cause Register).

Further, for both the callers of do_page_fault(): Prot-V / D-TLB-Miss,
the cause sub-fields in ECR are same for same type of access, making the
code much more simpler.

D-TLB-Miss [LD] 0x00_21_01_00
Prot-V     [LD] 0x00_23_01_00
                        ^^
D-TLB-Miss [ST] 0x00_21_02_00
Prot-V     [ST] 0x00_23_02_00
                        ^^
D-TLB-Miss [EX] 0x00_21_03_00
Prot-V     [EX] 0x00_23_03_00
                        ^^

This helps code consolidation, which is even better when moving code from
assembler to "C".

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/kernel/entry.S

@@ -355,8 +355,8 @@ ARC_ENTRY EV_TLBProtV
 	;  ecr and efa were not saved in case an Intr sneaks in
 	;  after fake rtie
 	;
-	lr  r3, [ecr]
-	lr  r4, [efa]
+	lr  r2, [ecr]
+	lr  r1, [efa]	; Faulting Data address
 
 	; --------(4) Return from CPU Exception Mode ---------
 	;  Fake a rtie, but rtie to next label
@@ -371,23 +371,17 @@ ARC_ENTRY EV_TLBProtV
 	;   -Access Violaton (WRITE to READ ONLY Page) - for linux COW
 	;   -Unaligned Access (READ/WRITE on odd boundary)
 	;
-	cmp r3, 0x230400    ; Misaligned data access ?
+	cmp r2, 0x230400    ; Misaligned data access ?
 	beq 4f
 
 	;========= (6a) Access Violation Processing ========
-	cmp r3, 0x230100
-	mov r1, 0x0              ; if LD exception ? write = 0
-	mov.ne r1, 0x1           ; else write = 1
-
-	mov r2, r4              ; faulting address
 	mov r0, sp              ; pt_regs
 	bl  do_page_fault
 	b   ret_from_exception
 
 	;========== (6b) Non aligned access ============
 4:
-	mov r0, r3              ; cause code
-	mov r1, r4              ; faulting address
+	mov r0, r2              ; cause code
 	mov r2, sp              ; pt_regs
 
 #ifdef  CONFIG_ARC_MISALIGN_ACCESS

arch/arc/mm/fault.c

@@ -52,7 +52,7 @@ bad_area:
 	return 1;
 }
 
-void do_page_fault(struct pt_regs *regs, int write, unsigned long address,
+void do_page_fault(struct pt_regs *regs, unsigned long address,
 		   unsigned long cause_code)
 {
 	struct vm_area_struct *vma = NULL;
@@ -60,6 +60,7 @@ void do_page_fault(struct pt_regs *regs, int write, unsigned long address,
 	struct mm_struct *mm = tsk->mm;
 	siginfo_t info;
 	int fault, ret;
+	int write = cause_code & (1 << ECR_C_BIT_DTLB_ST_MISS);  /* ST/EX */
 	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
 				(write ? FAULT_FLAG_WRITE : 0);
 

arch/arc/mm/tlbex.S

@@ -381,18 +381,8 @@ do_slow_path_pf:
 
 	; ------- setup args for Linux Page fault Hanlder ---------
 	mov_s r0, sp
-	lr  r2, [efa]
-	lr  r3, [ecr]
-
-	; Both st and ex imply WRITE access of some sort, hence do_page_fault( )
-	; invoked with write=1 for DTLB-st/ex Miss and write=0 for ITLB miss or
-	; DTLB-ld Miss
-	; DTLB Miss Cause code is ld = 0x01 , st = 0x02, ex = 0x03
-	; Following code uses that fact that st/ex have one bit in common
-
-	btst_s r3,  ECR_C_BIT_DTLB_ST_MISS
-	mov.z  r1, 0
-	mov.nz r1, 1
+	lr  r1, [efa]
+	lr  r2, [ecr]
 
 	; We don't want exceptions to be disabled while the fault is handled.
 	; Now that we have saved the context we return from exception hence