[MIPS] Fix fpu_save_double on 64-bit.

> Without this fix, _save_fp() in 64-bit kernel is seriously broken.
>
> ffffffff8010bec0 <_save_fp>:
> ffffffff8010bec0:       400d6000        mfc0    t1,c0_status
> ffffffff8010bec4:       000c7140        sll     t2,t0,0x5
> ffffffff8010bec8:       05c10011        bgez    t2,ffffffff8010bf10 <_save_fp+0x50>
> ffffffff8010becc:       00000000        nop
> ffffffff8010bed0:       f4810328        sdc1    $f1,808(a0)
> ...

Fix register usage in fpu_save_double() and make fpu_restore_double()
more symmetric with fpu_save_double().

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 8 insertions, 5 deletions

diff --git a/arch/mips/kernel/r4k_switch.S b/arch/mips/kernel/r4k_switch.S
index 0b1b54acee9f..db94e556fc97 100644
--- a/arch/mips/kernel/r4k_switch.S
+++ b/arch/mips/kernel/r4k_switch.S
@@ -75,8 +75,8 @@
         and     t0, t0, t1
         LONG_S  t0, ST_OFF(t3)
 
-        fpu_save_double a0 t1 t0 t2             # c0_status passed in t1
-                                                # clobbers t0 and t2
+        fpu_save_double a0 t0 t1                # c0_status passed in t0
+                                                # clobbers t1
 1:
 
         /*
@@ -129,9 +129,9 @@
  */
 LEAF(_save_fp)
 #ifdef CONFIG_64BIT
-        mfc0    t1, CP0_STATUS
+        mfc0    t0, CP0_STATUS
 #endif
-        fpu_save_double a0 t1 t0 t2             # clobbers t1
+        fpu_save_double a0 t0 t1                # clobbers t1
         jr      ra
         END(_save_fp)
 
@@ -139,7 +139,10 @@ LEAF(_save_fp)
  * Restore a thread's fp context.
  */
 LEAF(_restore_fp)
-        fpu_restore_double a0, t1               # clobbers t1
+#ifdef CONFIG_64BIT
+        mfc0    t0, CP0_STATUS
+#endif
+        fpu_restore_double a0 t0 t1             # clobbers t1
         jr      ra
         END(_restore_fp)