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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>
This commit is contained in:
Colin Cross 2012-05-07 17:57:42 -07:00 committed by Len Brown
parent 4126c0197b
commit 20ff51a36b
2 changed files with 41 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
drivers/cpuidle/coupled.c
View File

@ -129,6 +129,43 @@ static DEFINE_PER_CPU(struct call_single_data, cpuidle_coupled_poke_cb);
*/
static cpumask_t cpuidle_coupled_poked_mask;
/**
* cpuidle_coupled_parallel_barrier - synchronize all online coupled cpus
* @dev: cpuidle_device of the calling cpu
* @a: atomic variable to hold the barrier
*
* No caller to this function will return from this function until all online
* cpus in the same coupled group have called this function. Once any caller
* has returned from this function, the barrier is immediately available for
* reuse.
*
* The atomic variable a must be initialized to 0 before any cpu calls
* this function, will be reset to 0 before any cpu returns from this function.
*
* Must only be called from within a coupled idle state handler
* (state.enter when state.flags has CPUIDLE_FLAG_COUPLED set).
*
* Provides full smp barrier semantics before and after calling.
*/
void cpuidle_coupled_parallel_barrier(struct cpuidle_device *dev, atomic_t *a)
{
int n = dev->coupled->online_count;
smp_mb__before_atomic_inc();
atomic_inc(a);
while (atomic_read(a) < n)
cpu_relax();
if (atomic_inc_return(a) == n * 2) {
atomic_set(a, 0);
return;
}
while (atomic_read(a) > n)
cpu_relax();
}
/**
* cpuidle_state_is_coupled - check if a state is part of a coupled set
* @dev: struct cpuidle_device for the current cpu

4
include/linux/cpuidle.h
View File

@ -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 *
******************************/