sh: rework register restore code for sh3/sh4/sh4a

This patch reworks the sh3/sh4/sh4a register restore code in
the following ways:
 - break out restore_regs() from restore_all()
 - the register saving order is unchanged
 - use restore_regs() in sh_bios_handler and restore_all
 - document the function

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 33 insertions, 35 deletions

diff --git a/arch/sh/kernel/cpu/sh3/entry.S b/arch/sh/kernel/cpu/sh3/entry.S
index f3db143e70b2..cbffbffce351 100644
--- a/arch/sh/kernel/cpu/sh3/entry.S
+++ b/arch/sh/kernel/cpu/sh3/entry.S
@@ -188,44 +188,35 @@ call_dae:
 #if defined(CONFIG_SH_STANDARD_BIOS)
         /* Unwind the stack and jmp to the debug entry */
 ENTRY(sh_bios_handler)
-        mov.l   @r15+, r0
-        mov.l   @r15+, r1
-        mov.l   @r15+, r2
-        mov.l   @r15+, r3
-        mov.l   @r15+, r4
-        mov.l   @r15+, r5
-        mov.l   @r15+, r6
-        mov.l   @r15+, r7
-        stc     sr, r8
-        mov.l   1f, r9                  ! BL =1, RB=1, IMASK=0x0F
-        or      r9, r8
-        ldc     r8, sr                  ! here, change the register bank
-        mov.l   @r15+, r8
-        mov.l   @r15+, r9
-        mov.l   @r15+, r10
-        mov.l   @r15+, r11
-        mov.l   @r15+, r12
-        mov.l   @r15+, r13
-        mov.l   @r15+, r14
-        mov.l   @r15+, k0
-        ldc.l   @r15+, spc
-        lds.l   @r15+, pr
-        mov.l   @r15+, k1
-        ldc.l   @r15+, gbr
-        lds.l   @r15+, mach
-        lds.l   @r15+, macl
-        mov     k0, r15
+        mov.l   1f, r8
+        bsr     restore_regs
+         nop
+
+        lds     k2, pr                  ! restore pr
+        mov     k4, r15
         !
         mov.l   2f, k0
         mov.l   @k0, k0
         jmp     @k0
-         ldc    k1, ssr
+         ldc    k3, ssr
         .align  2
 1:      .long   0x300000f0
 2:      .long   gdb_vbr_vector
 #endif /* CONFIG_SH_STANDARD_BIOS */
 
-restore_all:
+! restore_regs()
+! - restore r0, r1, r2, r3, r4, r5, r6, r7 from the stack
+! - switch bank
+! - restore r8, r9, r10, r11, r12, r13, r14, r15 from the stack
+! - restore spc, pr*, ssr, gbr, mach, macl, skip default tra
+! k2 returns original pr
+! k3 returns original sr
+! k4 returns original stack pointer
+! r8 passes SR bitmask, overwritten with restored data on return
+! r9 trashed
+! BL=0 on entry, on exit BL=1 (depending on r8).
+
+restore_regs:
         mov.l   @r15+, r0
         mov.l   @r15+, r1
         mov.l   @r15+, r2
@@ -235,10 +226,9 @@ restore_all:
         mov.l   @r15+, r6
         mov.l   @r15+, r7
         !
-        stc     sr, r8
-        mov.l   7f, r9
-        or      r9, r8                  ! BL =1, RB=1
-        ldc     r8, sr                  ! here, change the register bank
+        stc     sr, r9
+        or      r8, r9
+        ldc     r9, sr
         !
         mov.l   @r15+, r8
         mov.l   @r15+, r9
@@ -249,12 +239,20 @@ restore_all:
         mov.l   @r15+, r14
         mov.l   @r15+, k4               ! original stack pointer
         ldc.l   @r15+, spc
-        lds.l   @r15+, pr
+        mov.l   @r15+, k2               ! original PR
         mov.l   @r15+, k3               ! original SR
         ldc.l   @r15+, gbr
         lds.l   @r15+, mach
         lds.l   @r15+, macl
-        add     #4, r15                 ! Skip syscall number
+        rts
+         add    #4, r15                 ! Skip syscall number
+
+restore_all:
+        mov.l   7f, r8
+        bsr     restore_regs
+         nop
+
+        lds     k2, pr                  ! restore pr
         !
 #ifdef CONFIG_SH_DSP
         mov.l   @r15+, k0               ! DSP mode marker