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authorBoris Ostrovsky <boris.ostrovsky@amd.com>2012-03-13 22:55:09 +0400
committerLen Brown <len.brown@intel.com>2012-03-30 11:23:01 +0400
commit1a022e3f1be11730bd8747b1af96a0274bf6356e (patch)
treed3c95b68626ac7d963ac3a85a07dae1cfc011906 /drivers/cpuidle
parente07510585a88c0f6c6c728e2e006aa913496d4ae (diff)
downloadlinux-1a022e3f1be11730bd8747b1af96a0274bf6356e.tar.xz
idle, x86: Allow off-lined CPU to enter deeper C states
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>
Diffstat (limited to 'drivers/cpuidle')
-rw-r--r--drivers/cpuidle/cpuidle.c28
1 files changed, 28 insertions, 0 deletions
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index f7cab5e9c4d6..3e146b2ada4a 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -72,6 +72,34 @@ 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
*
* NOTE: no locks or semaphores should be used here