diff options
author | Colin Cross <ccross@android.com> | 2012-05-08 00:57:42 (GMT) |
---|---|---|
committer | Len Brown <len.brown@intel.com> | 2012-06-02 04:49:36 (GMT) |
commit | 20ff51a36b2cd25ee7eb3216b6d02b68935435ba (patch) | |
tree | 3c50651ca3cdc64c409afe9f867c13a8d50200e0 | |
parent | 4126c0197bc8c58a0bb7fcda07b01b596b6fb4c5 (diff) | |
download | linux-20ff51a36b2cd25ee7eb3216b6d02b68935435ba.tar.xz |
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>
-rw-r--r-- | drivers/cpuidle/coupled.c | 37 | ||||
-rw-r--r-- | include/linux/cpuidle.h | 4 |
2 files changed, 41 insertions, 0 deletions
diff --git a/drivers/cpuidle/coupled.c b/drivers/cpuidle/coupled.c index aab6bba..2c9bf26 100644 --- a/drivers/cpuidle/coupled.c +++ b/drivers/cpuidle/coupled.c @@ -130,6 +130,43 @@ 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 * @drv: struct cpuidle_driver for the platform diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h index 6038448..5ab7183 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 * ******************************/ |