[RFC PATCH 09/16] MIPS: Introduce setup_kernel_mode macro

[Matt Redfearn <matt.redfearn@mips.com>]

There are several actions that need to be done on entry into the kernel.
Currently these actions are performed in a mix of get_saved_sp and
SAVE_SOME. This commit introduces a macro named setup_kernel_mode which
will eventually contain all of the necessary steps to be taken on entry
into the kernel from user mode. For a start, we need to set register $28
to its kernel conventional usage of the current thread info. Move this
from SAVE_SOME into setup_kernel_mode and invoke it in its place.

As part of the move, ensure that the Octeon code does not leave the .set
mips64 active by adding a .set push & .set pop around it.

Signed-off-by: Matt Redfearn <matt.redfearn@mips.com>
---

 arch/mips/include/asm/stackframe.h | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/arch/mips/include/asm/stackframe.h 
b/arch/mips/include/asm/stackframe.h
index 2161357cc68f..494fe41f5619 100644
--- a/arch/mips/include/asm/stackframe.h
+++ b/arch/mips/include/asm/stackframe.h
@@ -48,6 +48,19 @@
 #define STATMASK 0x1f
 #endif
 
+               .macro setup_kernel_mode docfi=0
+
+               /* Set thread_info if we're coming from user mode */
+               ori     $28, sp, _THREAD_MASK
+               xori    $28, _THREAD_MASK
+#ifdef CONFIG_CPU_CAVIUM_OCTEON
+               .set    push
+               .set    mips64
+               pref    0, 0($28)       /* Prefetch the current pointer */
+               .set    pop
+#endif
+               .endm
+
                .macro  SAVE_AT docfi=0
                .set    push
                .set    noat
@@ -273,17 +286,12 @@
                cfi_st  $25, PT_R25, \docfi
                cfi_st  $28, PT_R28, \docfi
 
-               /* Set thread_info if we're coming from user mode */
+               /* Set up kernel mode if we're coming from user */
                mfc0    k0, CP0_STATUS
                sll     k0, 3           /* extract cu0 bit */
                bltz    k0, 9f
 
-               ori     $28, sp, _THREAD_MASK
-               xori    $28, _THREAD_MASK
-#ifdef CONFIG_CPU_CAVIUM_OCTEON
-               .set    mips64
-               pref    0, 0($28)       /* Prefetch the current pointer */
-#endif
+               setup_kernel_mode \docfi
 9:
                .set    pop
                .endm
-- 
2.7.4