From 1a022e3f1be11730bd8747b1af96a0274bf6356e Mon Sep 17 00:00:00 2001 From: Boris Ostrovsky Date: Tue, 13 Mar 2012 19:55:09 +0100 Subject: 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 Signed-off-by: Len Brown --- drivers/cpuidle/cpuidle.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) (limited to 'drivers/cpuidle') diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index f7cab5e9c4d..3e146b2ada4 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -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 * -- cgit v1.2.3