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idle, x86: Allow off-lined CPU to enter deeper C states

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Currently when a CPU is off-lined it enters either MWAIT-based idle or,
if MWAIT is not desired or supported, HLT-based idle (which places the
processor in C1 state). This patch allows processors without MWAIT
support to stay in states deeper than C1.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@amd.com>
Signed-off-by: Len Brown <len.brown@intel.com>
This commit is contained in:
Boris Ostrovsky
2012-03-13 19:55:09 +01:00
committed by Len Brown
parent e07510585a
commit 1a022e3f1b
4 changed files with 67 additions and 1 deletions
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28
drivers/cpuidle/cpuidle.c
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@@ -71,6 +71,34 @@ typedef int (*cpuidle_enter_t)(struct cpuidle_device *dev,
static cpuidle_enter_t cpuidle_enter_ops;
/**
* cpuidle_play_dead - cpu off-lining
*
* Only returns in case of an error
*/
int cpuidle_play_dead(void)
{
struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
struct cpuidle_driver *drv = cpuidle_get_driver();
int i, dead_state = -1;
int power_usage = -1;
/* Find lowest-power state that supports long-term idle */
for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++) {
struct cpuidle_state *s = &drv->states[i];
if (s->power_usage < power_usage && s->enter_dead) {
power_usage = s->power_usage;
dead_state = i;
}
}
if (dead_state != -1)
return drv->states[dead_state].enter_dead(dev, dead_state);
return -ENODEV;
}
/**
* cpuidle_idle_call - the main idle loop
*