cpuidle: coupled: add parallel barrier function

Adds cpuidle_coupled_parallel_barrier, which can be used by coupled
cpuidle state enter functions to handle resynchronization after
determining if any cpu needs to abort.  The normal use case will
be:

static bool abort_flag;
static atomic_t abort_barrier;

int arch_cpuidle_enter(struct cpuidle_device *dev, ...)
{
	if (arch_turn_off_irq_controller()) {
	   	/* returns an error if an irq is pending and would be lost
		   if idle continued and turned off power */
		abort_flag = true;
	}

	cpuidle_coupled_parallel_barrier(dev, &abort_barrier);

	if (abort_flag) {
	   	/* One of the cpus didn't turn off it's irq controller */
	   	arch_turn_on_irq_controller();
		return -EINTR;
	}

	/* continue with idle */
	...
}

This will cause all cpus to abort idle together if one of them needs
to abort.

Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Tested-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index 603844835bc7..5ab7183313ce 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -183,6 +183,10 @@ static inline int cpuidle_play_dead(void) {return -ENODEV; }
 
 #endif
 
+#ifdef CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED
+void cpuidle_coupled_parallel_barrier(struct cpuidle_device *dev, atomic_t *a);
+#endif
+
 /******************************
  * CPUIDLE GOVERNOR INTERFACE *
  ******************************/