ARC: entry.S: comments cleanup

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

1 files changed, 20 insertions, 26 deletions

diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
index b120f3e1e13e..bd6dc892c7a8 100644
--- a/arch/arc/kernel/entry.S
+++ b/arch/arc/kernel/entry.S
@@ -322,13 +322,8 @@ ENTRY(EV_TLBProtV)
 
         EXCEPTION_PROLOGUE
 
-        ;---------(3) Save some more regs-----------------
-        ;  vineetg: Mar 6th: Random Seg Fault issue #1
-        ;  ecr and efa were not saved in case an Intr sneaks in
-        ;  after fake rtie
-
         lr  r2, [ecr]
-        lr  r0, [efa]   ; Faulting Data address
+        lr  r0, [efa]   ; Faulting Data addr (not part of pt_regs saved above)
 
         ; Exception auto-disables further Intr/exceptions.
         ; Re-enable them by pretending to return from exception
@@ -336,7 +331,7 @@ ENTRY(EV_TLBProtV)
 
         FAKE_RET_FROM_EXCPN
 
-        mov   r1, sp
+        mov   r1, sp    ; Handle to pt_regs
 
         ;------ (5) Type of Protection Violation? ----------
         ;
@@ -415,8 +410,11 @@ ENTRY(EV_Extension)
         b   ret_from_exception
 END(EV_Extension)
 
-;######################### System Call Tracing #########################
+;################ Trap Handling (Syscall, Breakpoint) ##################
 
+; ---------------------------------------------
+; syscall Tracing
+; ---------------------------------------------
 tracesys:
         ; save EFA in case tracer wants the PC of traced task
         ; using ERET won't work since next-PC has already committed
@@ -459,10 +457,9 @@ tracesys_exit:
         b   ret_from_exception ; NOT ret_from_system_call at is saves r0 which
         ; we'd done before calling post hook above
 
-;################### Break Point TRAP ##########################
-
-        ; ======= (5b) Trap is due to Break-Point =========
-
+; ---------------------------------------------
+; Breakpoint TRAP
+; ---------------------------------------------
 trap_with_param:
 
         ; stop_pc info by gdb needs this info
@@ -490,36 +487,33 @@ trap_with_param:
 
         b   ret_from_exception
 
-;##################### Trap Handling ##############################
-;
-; EV_Trap caused by TRAP_S and TRAP0 instructions.
-;------------------------------------------------------------------
-;   (1) System Calls
-;       :parameters in r0-r7.
-;       :r8 has the system call number
-;   (2) Break Points
-;------------------------------------------------------------------
+; ---------------------------------------------
+; syscall TRAP
+; ABI: (r0-r7) upto 8 args, (r8) syscall number
+; ---------------------------------------------
 
 ENTRY(EV_Trap)
 
         EXCEPTION_PROLOGUE
 
-        ;------- (4) What caused the Trap --------------
+        ;============ TRAP 1   :breakpoints
         lr     r10, [ecr]
         bmsk.f 0, r10, 7
         bnz    trap_with_param
 
-        ; ======= (5a) Trap is due to System Call ========
+        ;============ TRAP  (no param): syscall top level
 
+        ; First return from Exception to pure K mode (Exception/IRQs renabled)
         FAKE_RET_FROM_EXCPN
 
-        ; If syscall tracing ongoing, invoke pre-pos-hooks
+        ; If syscall tracing ongoing, invoke pre-post-hooks
         GET_CURR_THR_INFO_FLAGS   r10
         btst r10, TIF_SYSCALL_TRACE
         bnz tracesys  ; this never comes back
 
-        ;============ This is normal System Call case ==========
-        ; Sys-call num shd not exceed the total system calls avail
+        ;============ Normal syscall case
+
+        ; syscall num shd not exceed the total system calls avail
         cmp     r8,  NR_syscalls
         mov.hi  r0, -ENOSYS
         bhi     ret_from_system_call