[PATCH] intel_idle: replace conditionals with static_cpu_has(X86_FEATURE_ARAT)

[Jason Baron]

If the 'arat' cpu flag is set, then the conditionals in intel_idle() that
guard calling tick_broadcast_enter()/exit() will never be true. Use
static_cpu_has(X86_FEATURE_ARAT) to create a fast path to replace
the conditional.

Signed-off-by: Jason Baron <jba...@akamai.com>
Cc: Jacob Pan <jacob.jun....@linux.intel.com>
Cc: Len Brown <l...@kernel.org>
Cc: Rafael J. Wysocki <rafael.j.wyso...@intel.com>
---
 drivers/idle/intel_idle.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 5dc7ea4..5db5e31 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -913,8 +913,7 @@ static __cpuidle int intel_idle(struct cpuidle_device *dev,
        struct cpuidle_state *state = &drv->states[index];
        unsigned long eax = flg2MWAIT(state->flags);
        unsigned int cstate;
-
-       cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK) + 1;
+       bool uninitialized_var(tick);
 
        /*
         * NB: if CPUIDLE_FLAG_TLB_FLUSHED is set, this idle transition
@@ -923,12 +922,19 @@ static __cpuidle int intel_idle(struct cpuidle_device 
*dev,
         * useful with this knowledge.
         */
 
-       if (!(lapic_timer_reliable_states & (1 << (cstate))))
-               tick_broadcast_enter();
+       if (!static_cpu_has(X86_FEATURE_ARAT)) {
+               cstate = (((eax) >> MWAIT_SUBSTATE_SIZE) &
+                               MWAIT_CSTATE_MASK) + 1;
+               tick = false;
+               if (!(lapic_timer_reliable_states & (1 << (cstate)))) {
+                       tick = true;
+                       tick_broadcast_enter();
+               }
+       }
 
        mwait_idle_with_hints(eax, ecx);
 
-       if (!(lapic_timer_reliable_states & (1 << (cstate))))
+       if (!static_cpu_has(X86_FEATURE_ARAT) && tick)
                tick_broadcast_exit();
 
        return index;
-- 
2.6.1