ARC: entry.S: [arcompact] simplify SWITCH_TO_KERNEL_STK

Previously this macro was overloaded with stack switching, saving SP at right
slot in pt_regs, saving/setup of r25 and setting SP baseline to where
pt_regs->sp is saved (vs. bottom of pt_regs)

Now it only does SP switch, and leaves SP pointing to bottom of pt_regs.

r25 saving is no longer done here to allow for future reordering of
regfile in pt_regs w/o touching this macro

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

diff --git a/arch/arc/include/asm/entry-compact.h b/arch/arc/include/asm/entry-compact.h
index 8b65eb36655abd5a50513d075aa08be92a9efcb6..1174ddd4cac894bc9ccde0a254ce12981a49639d 100644 (file)
--- a/arch/arc/include/asm/entry-compact.h
+++ b/arch/arc/include/asm/entry-compact.h
@@ -39,8 +39,8 @@
  * Switch to Kernel Mode stack if SP points to User Mode stack
  *
  * Entry   : r9 contains pre-IRQ/exception/trap status32
- * Exit    : SP is set to kernel mode stack pointer
- *           If CURR_IN_REG, r25 set to "current" task pointer
+ * Exit    : SP set to K mode stack
+ *           SP at the time of entry (K/U) saved @ pt_regs->sp
  * Clobbers: r9
  *-------------------------------------------------------------*/
 
@@ -80,12 +80,11 @@
 
 #endif
 
-       /* Save Pre Intr/Exception KERNEL MODE SP on kernel stack
-        * safe-keeping not really needed, but it keeps the epilogue code
-        * (SP restore) simpler/uniform.
-        */
+    /*------Intr/Ecxp happened in kernel mode, SP already setup ------ */
+       /* save it nevertheless @ pt_regs->sp for uniformity */
+
        b.d     66f
-       mov     r9, sp
+       st      sp, [sp, PT_sp - SZ_PT_REGS]
 
 88: /*------Intr/Ecxp happened in user mode, "switch" stack ------ */
 
@@ -94,30 +93,12 @@
        /* With current tsk in r9, get it's kernel mode stack base */
        GET_TSK_STACK_BASE  r9, r9
 
-66:
-#ifdef CONFIG_ARC_CURR_IN_REG
-       /*
-        * Treat r25 as scratch reg, save it on stack first
-        * Load it with current task pointer
-        */
-       st      r25, [r9, -4]
-       GET_CURR_TASK_ON_CPU   r25
-#endif
-
-       /* Save Pre Intr/Exception User SP on kernel stack */
-       st.a    sp, [r9, -16]   ; Make room for orig_r0, ECR, user_r25
-
-       /* CAUTION:
-        * SP should be set at the very end when we are done with everything
-        * In case of 2 levels of interrupt we depend on value of SP to assume
-        * that everything else is done (loading r25 etc)
-        */
-
-       /* set SP to point to kernel mode stack */
-       mov sp, r9
-
-       /* ----- Stack Switched to kernel Mode, Now save REG FILE ----- */
+       /* save U mode SP @ pt_regs->sp */
+       st      sp, [r9, PT_sp - SZ_PT_REGS]
 
+       /* final SP switch */
+       mov     sp, r9
+66:
 .endm
 
 /*------------------------------------------------------------
@@ -181,11 +162,21 @@
        /* ARC700 doesn't provide auto-stack switching */
        SWITCH_TO_KERNEL_STK
 
-       st      r0, [sp, 4]    /* orig_r0, needed only for sys calls */
+#ifdef CONFIG_ARC_CURR_IN_REG
+       /* Treat r25 as scratch reg (save on stack) and load with "current" */
+       PUSH    r25
+       GET_CURR_TASK_ON_CPU   r25
+#else
+       sub     sp, sp, 4
+#endif
+
+       st.a    r0, [sp, -8]    /* orig_r0 needed for syscall (skip ECR slot) */
+       sub     sp, sp, 4       /* skip pt_regs->sp, already saved above */
 
        /* Restore r9 used to code the early prologue */
        PROLOG_RESTORE_REG  r9, @ex_saved_reg1
 
+       /* now we are ready to save the regfile */
        SAVE_R0_TO_R12
        PUSH    gp
        PUSH    fp
@@ -245,12 +236,20 @@
 
        SWITCH_TO_KERNEL_STK
 
-       /* restore original r9 */
-       PROLOG_RESTORE_REG  r9, @int\LVL\()_saved_reg
+#ifdef CONFIG_ARC_CURR_IN_REG
+       /* Treat r25 as scratch reg (save on stack) and load with "current" */
+       PUSH    r25
+       GET_CURR_TASK_ON_CPU   r25
+#else
+       sub     sp, sp, 4
+#endif
 
-       /* now we are ready to save the remaining context */
-       st      0x003\LVL\()abcd, [sp, 8]    /* Dummy ECR */
-       st      0, [sp, 4]    /* orig_r0 , N/A for IRQ */
+       PUSH    0x003\LVL\()abcd    /* Dummy ECR */
+       sub     sp, sp, 8           /* skip orig_r0 (not needed)
+                                      skip pt_regs->sp, already saved above */
+
+       /* Restore r9 used to code the early prologue */
+       PROLOG_RESTORE_REG  r9, @int\LVL\()_saved_reg
 
        SAVE_R0_TO_R12
        PUSH    gp