m68knommu: use user stack pointer hardware on some ColdFire cores

The more modern ColdFire parts (even if based on older version cores)
have separate user and supervisor stack pointers (a7 register).
Modify the ColdFire CPU setup and exception code to enable and use
this on parts that have it.

Signed-off-by: Greg Ungerer <gerg@uclinux.org>

1 files changed, 34 insertions, 25 deletions

diff --git a/arch/m68k/include/asm/entry_no.h b/arch/m68k/include/asm/entry_no.h
index 26be277394f9..627d69bacc58 100644
--- a/arch/m68k/include/asm/entry_no.h
+++ b/arch/m68k/include/asm/entry_no.h
@@ -42,12 +42,16 @@
  */
 
 #ifdef CONFIG_COLDFIRE
+#ifdef CONFIG_COLDFIRE_SW_A7
 /*
- * This is made a little more tricky on the ColdFire. There is no
- * separate kernel and user stack pointers. Need to artificially
+ * This is made a little more tricky on older ColdFires. There is no
+ * separate supervisor and user stack pointers. Need to artificially
  * construct a usp in software... When doing this we need to disable
- * interrupts, otherwise bad things could happen.
+ * interrupts, otherwise bad things will happen.
  */
+.globl sw_usp
+.globl sw_ksp
+
 .macro SAVE_ALL
         move    #0x2700,%sr             /* disable intrs */
         btst    #5,%sp@(2)              /* from user? */
@@ -74,9 +78,7 @@
         7:
 .endm
 
-.macro RESTORE_ALL
-        btst    #5,%sp@(PT_SR)          /* going user? */
-        bnes    8f                      /* no, skip */
+.macro RESTORE_USER
         move    #0x2700,%sr             /* disable intrs */
         movel   sw_usp,%a0              /* get usp */
         movel   %sp@(PT_OFF_PC),%a0@-   /* copy exception program counter */
@@ -91,19 +93,22 @@
         subql   #8,sw_usp               /* set exception */
         movel   sw_usp,%sp              /* restore usp */
         rte
-        8:
-        moveml  %sp@,%d1-%d5/%a0-%a2
-        lea     %sp@(32),%sp            /* space for 8 regs */
-        movel   %sp@+,%d0
-        addql   #4,%sp                  /* orig d0 */
-        addl    %sp@+,%sp               /* stkadj */
-        rte
 .endm
 
+.macro RDUSP
+        movel   sw_usp,%a2
+.endm
+
+.macro WRUSP
+        movel   %a0,sw_usp
+.endm
+
+#else /* !CONFIG_COLDFIRE_SW_A7 */
 /*
- * Quick exception save, use current stack only.
+ * Modern ColdFire parts have separate supervisor and user stack
+ * pointers. Simple load and restore macros for this case.
  */
-.macro SAVE_LOCAL
+.macro SAVE_ALL
         move    #0x2700,%sr             /* disable intrs */
         clrl    %sp@-                   /* stkadj */
         movel   %d0,%sp@-               /* orig d0 */
@@ -112,7 +117,7 @@
         moveml  %d1-%d5/%a0-%a2,%sp@
 .endm
 
-.macro RESTORE_LOCAL
+.macro RESTORE_USER
         moveml  %sp@,%d1-%d5/%a0-%a2
         lea     %sp@(32),%sp            /* space for 8 regs */
         movel   %sp@+,%d0
@@ -121,6 +126,18 @@
         rte
 .endm
 
+.macro RDUSP
+        /*move  %usp,%a2*/
+        .word   0x4e6a
+.endm
+
+.macro WRUSP
+        /*move  %a0,%usp*/
+        .word   0x4e60
+.endm
+
+#endif /* !CONFIG_COLDFIRE_SW_A7 */
+
 .macro SAVE_SWITCH_STACK
         lea     %sp@(-24),%sp           /* 6 regs */
         moveml  %a3-%a6/%d6-%d7,%sp@
@@ -131,14 +148,6 @@
         lea     %sp@(24),%sp            /* 6 regs */
 .endm
 
-/*
- * Software copy of the user and kernel stack pointers... Ugh...
- * Need these to get around ColdFire not having separate kernel
- * and user stack pointers.
- */
-.globl sw_usp
-.globl sw_ksp
-
 #else /* !CONFIG_COLDFIRE */
 
 /*
@@ -167,6 +176,6 @@
         moveml  %sp@+,%a3-%a6/%d6-%d7
 .endm
 
-#endif /* !CONFIG_COLDFIRE */
+#endif /* !COLDFIRE_SW_A7 */
 #endif /* __ASSEMBLY__ */
 #endif /* __M68KNOMMU_ENTRY_H */