[PATCH v3]PM/Sleep: Timer quiesce in freeze state

From: Li, Aubrey
Date: Mon Dec 08 2014 - 22:02:10 EST

The patch is based on v3.18.

Freeze is a general power saving state that processes are frozen, devices
are suspended and CPUs are in idle state. However, when the system enters
freeze state, there are a few timers keep ticking and hence consumes more
power unnecessarily. The observed timer events in freeze state are:
- tick_sched_timer
- watchdog lockup detector
- realtime scheduler period timer

The system power consumption in freeze state will be reduced significantly
if we quiesce these timers.

The patch is tested on:
- Sandybrdige-EP system, both RTC alarm and power button are able to wake
the system up from freeze state.
- HP laptop EliteBook 8460p, both RTC alarm and power button are able to
wake the system up from freeze state.
- Baytrail-T(ASUS_T100) platform, power button is able to wake the system
up from freeze state.

Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Aubrey Li <aubrey.li@xxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Cc: Len Brown <len.brown@xxxxxxxxx>
Cc: Alan Cox <alan@xxxxxxxxxxxxxxx>
---
drivers/cpuidle/cpuidle.c | 13 ++++++++
include/linux/clockchips.h | 4 +++
include/linux/suspend.h | 4 +++
include/linux/timekeeping.h | 2 ++
kernel/power/suspend.c | 50 ++++++++++++++++++++++++++---
kernel/sched/idle.c | 45 ++++++++++++++++++++++++++
kernel/softirq.c | 5 +--
kernel/time/clockevents.c | 13 ++++++++
kernel/time/tick-common.c | 53 +++++++++++++++++++++++++++++++
kernel/time/tick-internal.h | 3 ++
kernel/time/timekeeping.c | 77 +++++++++++++++++++++++++++++++++------------
11 files changed, 243 insertions(+), 26 deletions(-)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 125150d..b9a3ada 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -20,6 +20,7 @@
#include <linux/hrtimer.h>
#include <linux/module.h>
#include <trace/events/power.h>
+#include <linux/suspend.h>

#include "cpuidle.h"

@@ -119,6 +120,18 @@ int cpuidle_enter_state(struct cpuidle_device *dev, struct cpuidle_driver *drv,
ktime_t time_start, time_end;
s64 diff;

+ /*
+ * under the freeze scenario, the timekeeping is suspended
+ * as well as the clock source device, so we bypass the idle
+ * counter update in freeze idle
+ */
+ if (in_freeze()) {
+ entered_state = target_state->enter(dev, drv, index);
+ if (!cpuidle_state_is_coupled(dev, drv, entered_state))
+ local_irq_enable();
+ return entered_state;
+ }
+
trace_cpu_idle_rcuidle(index, dev->cpu);
time_start = ktime_get();

diff --git a/include/linux/clockchips.h b/include/linux/clockchips.h
index 2e4cb67..d118e0b 100644
--- a/include/linux/clockchips.h
+++ b/include/linux/clockchips.h
@@ -18,6 +18,9 @@ enum clock_event_nofitiers {
CLOCK_EVT_NOTIFY_BROADCAST_EXIT,
CLOCK_EVT_NOTIFY_SUSPEND,
CLOCK_EVT_NOTIFY_RESUME,
+ CLOCK_EVT_NOTIFY_FREEZE_PREPARE,
+ CLOCK_EVT_NOTIFY_FREEZE,
+ CLOCK_EVT_NOTIFY_UNFREEZE,
CLOCK_EVT_NOTIFY_CPU_DYING,
CLOCK_EVT_NOTIFY_CPU_DEAD,
};
@@ -95,6 +98,7 @@ enum clock_event_mode {
*/
struct clock_event_device {
void (*event_handler)(struct clock_event_device *);
+ void (*real_handler)(struct clock_event_device *);
int (*set_next_event)(unsigned long evt,
struct clock_event_device *);
int (*set_next_ktime)(ktime_t expires,
diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 3388c1b..86a651c 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h
@@ -203,6 +203,8 @@ extern void suspend_set_ops(const struct platform_suspend_ops *ops);
extern int suspend_valid_only_mem(suspend_state_t state);
extern void freeze_set_ops(const struct platform_freeze_ops *ops);
extern void freeze_wake(void);
+extern bool in_freeze(void);
+extern bool idle_should_freeze(void);

/**
* arch_suspend_disable_irqs - disable IRQs for suspend
@@ -230,6 +232,8 @@ static inline void suspend_set_ops(const struct platform_suspend_ops *ops) {}
static inline int pm_suspend(suspend_state_t state) { return -ENOSYS; }
static inline void freeze_set_ops(const struct platform_freeze_ops *ops) {}
static inline void freeze_wake(void) {}
+static inline bool in_freeze(void) { return false; }
+static inline bool idle_should_freeze(void) { return false; }
#endif /* !CONFIG_SUSPEND */

/* struct pbe is used for creating lists of pages that should be restored
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 1caa6b0..07957a9 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h
@@ -5,6 +5,8 @@

void timekeeping_init(void);
extern int timekeeping_suspended;
+extern void timekeeping_freeze(void);
+extern void timekeeping_unfreeze(void);

/*
* Get and set timeofday
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index c347e3c..6467fb8 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -28,6 +28,7 @@
#include <linux/ftrace.h>
#include <trace/events/power.h>
#include <linux/compiler.h>
+#include <linux/clockchips.h>

#include "power.h"

@@ -37,7 +38,15 @@ const char *pm_states[PM_SUSPEND_MAX];
static const struct platform_suspend_ops *suspend_ops;
static const struct platform_freeze_ops *freeze_ops;
static DECLARE_WAIT_QUEUE_HEAD(suspend_freeze_wait_head);
-static bool suspend_freeze_wake;
+
+/* freeze state machine */
+enum freeze_state {
+ FREEZE_STATE_NONE, /* not in freeze */
+ FREEZE_STATE_ENTER, /* enter freeze */
+ FREEZE_STATE_WAKE, /* in freeze wakeup context */
+};
+
+static enum freeze_state suspend_freeze_state;

void freeze_set_ops(const struct platform_freeze_ops *ops)
{
@@ -46,23 +55,56 @@ void freeze_set_ops(const struct platform_freeze_ops *ops)
unlock_system_sleep();
}

+bool in_freeze(void)
+{
+ return (suspend_freeze_state > FREEZE_STATE_NONE);
+}
+EXPORT_SYMBOL_GPL(in_freeze);
+
+bool idle_should_freeze(void)
+{
+ return (suspend_freeze_state == FREEZE_STATE_ENTER);
+}
+EXPORT_SYMBOL_GPL(idle_should_freeze);
+
static void freeze_begin(void)
{
- suspend_freeze_wake = false;
+ suspend_freeze_state = FREEZE_STATE_NONE;
}

static void freeze_enter(void)
{
+ suspend_freeze_state = FREEZE_STATE_ENTER;
+ get_online_cpus();
cpuidle_use_deepest_state(true);
cpuidle_resume();
- wait_event(suspend_freeze_wait_head, suspend_freeze_wake);
+ clockevents_notify(CLOCK_EVT_NOTIFY_FREEZE_PREPARE, NULL);
+ /*
+ * push all the CPUs into freeze idle loop
+ */
+ wake_up_all_idle_cpus();
+ printk(KERN_INFO "PM: suspend to idle\n");
+ /*
+ * put the current CPU into wait queue so that this CPU
+ * is able to enter freeze idle loop as well
+ */
+ wait_event(suspend_freeze_wait_head,
+ (suspend_freeze_state == FREEZE_STATE_WAKE));
+ printk(KERN_INFO "PM: resume from freeze\n");
cpuidle_pause();
cpuidle_use_deepest_state(false);
+ put_online_cpus();
+ suspend_freeze_state = FREEZE_STATE_NONE;
}

void freeze_wake(void)
{
- suspend_freeze_wake = true;
+ if (!in_freeze())
+ return;
+ /*
+ * wake freeze task up
+ */
+ suspend_freeze_state = FREEZE_STATE_WAKE;
wake_up(&suspend_freeze_wait_head);
}
EXPORT_SYMBOL_GPL(freeze_wake);
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index c47fce7..f28f8cb 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -7,6 +7,7 @@
#include <linux/tick.h>
#include <linux/mm.h>
#include <linux/stackprotector.h>
+#include <linux/suspend.h>

#include <asm/tlb.h>

@@ -182,6 +183,45 @@ exit_idle:
}

/*
+ * cpu idle freeze function
+ */
+static void cpu_idle_freeze(void)
+{
+ struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
+ struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
+
+ /*
+ * suspend tick, the last CPU suspend timekeeping
+ */
+ clockevents_notify(CLOCK_EVT_NOTIFY_FREEZE, NULL);
+ /*
+ * idle loop here if idle_should_freeze()
+ */
+ while (idle_should_freeze()) {
+ int next_state;
+ /*
+ * interrupt must be disabled before cpu enters idle
+ */
+ local_irq_disable();
+
+ next_state = cpuidle_select(drv, dev);
+ if (next_state < 0) {
+ arch_cpu_idle();
+ continue;
+ }
+ /*
+ * cpuidle_enter will return with interrupt enabled
+ */
+ cpuidle_enter(drv, dev, next_state);
+ }
+
+ /*
+ * resume tick, the first wakeup CPU resume timekeeping
+ */
+ clockevents_notify(CLOCK_EVT_NOTIFY_UNFREEZE, NULL);
+}
+
+/*
* Generic idle loop implementation
*
* Called with polling cleared.
@@ -208,6 +248,11 @@ static void cpu_idle_loop(void)
if (cpu_is_offline(smp_processor_id()))
arch_cpu_idle_dead();

+ if (idle_should_freeze()) {
+ cpu_idle_freeze();
+ continue;
+ }
+
local_irq_disable();
arch_cpu_idle_enter();

diff --git a/kernel/softirq.c b/kernel/softirq.c
index 0699add..a231bf6 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -26,6 +26,7 @@
#include <linux/smpboot.h>
#include <linux/tick.h>
#include <linux/irq.h>
+#include <linux/suspend.h>

#define CREATE_TRACE_POINTS
#include <trace/events/irq.h>
@@ -321,7 +322,7 @@ asmlinkage __visible void do_softirq(void)
void irq_enter(void)
{
rcu_irq_enter();
- if (is_idle_task(current) && !in_interrupt()) {
+ if (is_idle_task(current) && !in_interrupt() && !in_freeze()) {
/*
* Prevent raise_softirq from needlessly waking up ksoftirqd
* here, as softirq will be serviced on return from interrupt.
@@ -364,7 +365,7 @@ static inline void tick_irq_exit(void)

/* Make sure that timer wheel updates are propagated */
if ((idle_cpu(cpu) && !need_resched()) || tick_nohz_full_cpu(cpu)) {
- if (!in_interrupt())
+ if (!in_interrupt() && !in_freeze())
tick_nohz_irq_exit();
}
#endif
diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 5544990..6d9a4a3 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -17,6 +17,7 @@
#include <linux/module.h>
#include <linux/smp.h>
#include <linux/device.h>
+#include <linux/suspend.h>

#include "tick-internal.h"

@@ -579,6 +580,18 @@ int clockevents_notify(unsigned long reason, void *arg)
tick_resume();
break;

+ case CLOCK_EVT_NOTIFY_FREEZE_PREPARE:
+ tick_freeze_prepare();
+ break;
+
+ case CLOCK_EVT_NOTIFY_FREEZE:
+ tick_freeze();
+ break;
+
+ case CLOCK_EVT_NOTIFY_UNFREEZE:
+ tick_unfreeze();
+ break;
+
case CLOCK_EVT_NOTIFY_CPU_DEAD:
tick_shutdown_broadcast_oneshot(arg);
tick_shutdown_broadcast(arg);
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 7efeedf..0bbc886 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -19,6 +19,7 @@
#include <linux/profile.h>
#include <linux/sched.h>
#include <linux/module.h>
+#include <linux/suspend.h>

#include <asm/irq_regs.h>

@@ -51,6 +52,16 @@ ktime_t tick_period;
int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;

/*
+ * Tick device is per CPU device, when we freeze the timekeeping stuff, we
+ * want to freeze the tick device on all of the online CPUs.
+ *
+ * tick_freeze_target_depth is a counter used for freezing tick device, the
+ * initial value of it is online CPU number. When it is counted down to ZERO,
+ * all of the tick devices are freezed.
+ */
+static unsigned int tick_freeze_target_depth;
+
+/*
* Debugging: see timer_list.c
*/
struct tick_device *tick_get_device(int cpu)
@@ -375,15 +386,21 @@ void tick_shutdown(unsigned int *cpup)
void tick_suspend(void)
{
struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+ struct clock_event_device *dev = td->evtdev;

+ dev->real_handler = dev->event_handler;
+ dev->event_handler = clockevents_handle_noop;
clockevents_shutdown(td->evtdev);
}

void tick_resume(void)
{
struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
+ struct clock_event_device *dev = td->evtdev;
int broadcast = tick_resume_broadcast();

+ dev->event_handler = dev->real_handler;
+ dev->real_handler = NULL;
clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);

if (!broadcast) {
@@ -394,6 +411,42 @@ void tick_resume(void)
}
}

+void tick_freeze_prepare(void)
+{
+ tick_freeze_target_depth = num_online_cpus();
+}
+
+void tick_freeze(void)
+{
+ /*
+ * This is serialized against a concurrent wakeup
+ * via clockevents_lock
+ */
+ tick_freeze_target_depth--;
+ tick_suspend();
+
+ /*
+ * the last tick_suspend CPU suspends timekeeping
+ */
+ if (!tick_freeze_target_depth)
+ timekeeping_freeze();
+}
+
+void tick_unfreeze(void)
+{
+ /*
+ * the first wakeup CPU resumes timekeeping
+ */
+ if (timekeeping_suspended) {
+ timekeeping_unfreeze();
+ touch_softlockup_watchdog();
+ tick_resume();
+ hrtimers_resume();
+ } else {
+ tick_resume();
+ }
+}
+
/**
* tick_init - initialize the tick control
*/
diff --git a/kernel/time/tick-internal.h b/kernel/time/tick-internal.h
index 366aeb4..8b5bab6 100644
--- a/kernel/time/tick-internal.h
+++ b/kernel/time/tick-internal.h
@@ -27,6 +27,9 @@ extern void tick_handover_do_timer(int *cpup);
extern void tick_shutdown(unsigned int *cpup);
extern void tick_suspend(void);
extern void tick_resume(void);
+extern void tick_freeze_prepare(void);
+extern void tick_freeze(void);
+extern void tick_unfreeze(void);
extern bool tick_check_replacement(struct clock_event_device *curdev,
struct clock_event_device *newdev);
extern void tick_install_replacement(struct clock_event_device *dev);
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index ec1791f..a11065f 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c
@@ -1107,14 +1107,7 @@ void timekeeping_inject_sleeptime(struct timespec *delta)
clock_was_set();
}

-/**
- * timekeeping_resume - Resumes the generic timekeeping subsystem.
- *
- * This is for the generic clocksource timekeeping.
- * xtime/wall_to_monotonic/jiffies/etc are
- * still managed by arch specific suspend/resume code.
- */
-static void timekeeping_resume(void)
+static void timekeeping_resume_compensate_time(void)
{
struct timekeeper *tk = &tk_core.timekeeper;
struct clocksource *clock = tk->tkr.clock;
@@ -1127,9 +1120,6 @@ static void timekeeping_resume(void)
read_persistent_clock(&tmp);
ts_new = timespec_to_timespec64(tmp);

- clockevents_resume();
- clocksource_resume();
-
raw_spin_lock_irqsave(&timekeeper_lock, flags);
write_seqcount_begin(&tk_core.seq);

@@ -1186,16 +1176,9 @@ static void timekeeping_resume(void)
timekeeping_update(tk, TK_MIRROR | TK_CLOCK_WAS_SET);
write_seqcount_end(&tk_core.seq);
raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
-
- touch_softlockup_watchdog();
-
- clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
-
- /* Resume hrtimers */
- hrtimers_resume();
}

-static int timekeeping_suspend(void)
+static void timekeeping_suspend_get_time(void)
{
struct timekeeper *tk = &tk_core.timekeeper;
unsigned long flags;
@@ -1242,11 +1225,65 @@ static int timekeeping_suspend(void)
timekeeping_update(tk, TK_MIRROR);
write_seqcount_end(&tk_core.seq);
raw_spin_unlock_irqrestore(&timekeeper_lock, flags);
+}

- clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
+/*
+ * The following operations:
+ * clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
+ * clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
+ * are moved out of
+ * timekeeping_freeze() and timekeeping_unfreeze()
+ * and, replaced by
+ * tick_suspend() and tick_resume()
+ * and, put into:
+ * tick_freeze() and tick_unfreeze()
+ * so we avoid clockevents_lock multiple access
+ */
+void timekeeping_freeze(void)
+{
+ /*
+ * clockevents_lock being held
+ */
+ timekeeping_suspend_get_time();
clocksource_suspend();
clockevents_suspend();
+}

+void timekeeping_unfreeze(void)
+{
+ /*
+ * clockevents_lock being held
+ */
+ clockevents_resume();
+ clocksource_resume();
+ timekeeping_resume_compensate_time();
+}
+
+/**
+ * timekeeping_resume - Resumes the generic timekeeping subsystem.
+ *
+ * This is for the generic clocksource timekeeping.
+ * xtime/wall_to_monotonic/jiffies/etc are
+ * still managed by arch specific suspend/resume code.
+ */
+static void timekeeping_resume(void)
+{
+ clockevents_resume();
+ clocksource_resume();
+ timekeeping_resume_compensate_time();
+
+ touch_softlockup_watchdog();
+ clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
+ /* Resume hrtimers */
+ hrtimers_resume();
+}
+
+static int timekeeping_suspend(void)
+{
+ timekeeping_suspend_get_time();
+ clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
+ clocksource_suspend();
+ clockevents_suspend();
return 0;
}

--
1.9.1
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/