[PATCH 12/13] powerpc/64: runlatch CTRL[RUN] set optimisation

[Nicholas Piggin]

The CTRL register is read-only except bit 63 which is the run latch
control. This means it can be updated with a mtspr rather than
mfspr/mtspr.

Reviewed-by: Vaidyanathan Srinivasan <sva...@linux.vnet.ibm.com>
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
 arch/powerpc/kernel/process.c | 12 ++----------
 1 file changed, 2 insertions(+), 10 deletions(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index baae104b16c7..a44ea034c226 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1960,12 +1960,8 @@ void show_stack(struct task_struct *tsk, unsigned long 
*stack)
 void notrace __ppc64_runlatch_on(void)
 {
        struct thread_info *ti = current_thread_info();
-       unsigned long ctrl;
-
-       ctrl = mfspr(SPRN_CTRLF);
-       ctrl |= CTRL_RUNLATCH;
-       mtspr(SPRN_CTRLT, ctrl);
 
+       mtspr(SPRN_CTRLT, CTRL_RUNLATCH);
        ti->local_flags |= _TLF_RUNLATCH;
 }
 
@@ -1973,13 +1969,9 @@ void notrace __ppc64_runlatch_on(void)
 void notrace __ppc64_runlatch_off(void)
 {
        struct thread_info *ti = current_thread_info();
-       unsigned long ctrl;
 
        ti->local_flags &= ~_TLF_RUNLATCH;
-
-       ctrl = mfspr(SPRN_CTRLF);
-       ctrl &= ~CTRL_RUNLATCH;
-       mtspr(SPRN_CTRLT, ctrl);
+       mtspr(SPRN_CTRLT, 0);
 }
 #endif /* CONFIG_PPC64 */
 
-- 
2.11.0