[PATCH 1/2] cpuidle: Avoid calls to cpuidle_resume|pause() for s2idle

Ulf Hansson
2021-09-29T14:45:02Z

In s2idle_enter(), cpuidle_resume|pause() are invoked to re-allow calls to
the cpuidle callbacks during s2idle operations. This is needed because
cpuidle is paused in-between in dpm_suspend_noirq() and dpm_resume_noirq().

However, calling cpuidle_resume|pause() from s2idle_enter() looks a bit
superfluous, as it also causes all CPUs to be waken up when the first CPU
wakes up from s2idle.

Therefore, let's drop the calls to cpuidle_resume|pause() from
s2idle_enter(). To make this work, let's also adopt the path in the
cpuidle_idle_call() to allow cpuidle callbacks to be invoked for s2idle,
even if cpuidle has been paused.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
---
drivers/cpuidle/cpuidle.c | 7 ++++++-
include/linux/cpuidle.h | 2 ++
kernel/power/suspend.c | 2 --
kernel/sched/idle.c | 40 ++++++++++++++++++++++-----------------
4 files changed, 31 insertions(+), 20 deletions(-)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index ef2ea1b12cd8..c76747e497e7 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -49,7 +49,12 @@ void disable_cpuidle(void)
bool cpuidle_not_available(struct cpuidle_driver *drv,
struct cpuidle_device *dev)
{
- return off || !initialized || !drv || !dev || !dev->enabled;
+ return off || !drv || !dev || !dev->enabled;
+}
+
+bool cpuidle_paused(void)
+{
+ return !initialized;
}

/**
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index fce476275e16..51698b385ab5 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -165,6 +165,7 @@ extern void cpuidle_pause_and_lock(void);
extern void cpuidle_resume_and_unlock(void);
extern void cpuidle_pause(void);
extern void cpuidle_resume(void);
+extern bool cpuidle_paused(void);
extern int cpuidle_enable_device(struct cpuidle_device *dev);
extern void cpuidle_disable_device(struct cpuidle_device *dev);
extern int cpuidle_play_dead(void);
@@ -204,6 +205,7 @@ static inline void cpuidle_pause_and_lock(void) { }
static inline void cpuidle_resume_and_unlock(void) { }
static inline void cpuidle_pause(void) { }
static inline void cpuidle_resume(void) { }
+static inline bool cpuidle_paused(void) {return true; }
static inline int cpuidle_enable_device(struct cpuidle_device *dev)
{return -ENODEV; }
static inline void cpuidle_disable_device(struct cpuidle_device *dev) { }
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index eb75f394a059..388a5de4836e 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -97,7 +97,6 @@ static void s2idle_enter(void)
raw_spin_unlock_irq(&s2idle_lock);

cpus_read_lock();
- cpuidle_resume();

/* Push all the CPUs into the idle loop. */
wake_up_all_idle_cpus();
@@ -105,7 +104,6 @@ static void s2idle_enter(void)
swait_event_exclusive(s2idle_wait_head,
s2idle_state == S2IDLE_STATE_WAKE);

- cpuidle_pause();
cpus_read_unlock();

raw_spin_lock_irq(&s2idle_lock);
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index d17b0a5ce6ac..3bc3a2c46731 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -158,6 +158,17 @@ static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
return cpuidle_enter(drv, dev, next_state);
}

+static void cpuidle_deepest_state(struct cpuidle_driver *drv,
+ struct cpuidle_device *dev,
+ u64 max_latency_ns)
+{
+ int next_state;
+
+ tick_nohz_idle_stop_tick();
+ next_state = cpuidle_find_deepest_state(drv, dev, max_latency_ns);
+ call_cpuidle(drv, dev, next_state);
+}
+
/**
* cpuidle_idle_call - the main idle function
*
@@ -189,6 +200,7 @@ static void cpuidle_idle_call(void)
*/

if (cpuidle_not_available(drv, dev)) {
+default_idle:
tick_nohz_idle_stop_tick();

default_idle_call();
@@ -204,25 +216,19 @@ static void cpuidle_idle_call(void)
* timekeeping to prevent timer interrupts from kicking us out of idle
* until a proper wakeup interrupt happens.
*/
+ if (idle_should_enter_s2idle()) {
+ entered_state = call_cpuidle_s2idle(drv, dev);
+ if (entered_state <= 0)
+ cpuidle_deepest_state(drv, dev, U64_MAX);
+ goto exit_idle;
+ }

- if (idle_should_enter_s2idle() || dev->forced_idle_latency_limit_ns) {
- u64 max_latency_ns;
-
- if (idle_should_enter_s2idle()) {
-
- entered_state = call_cpuidle_s2idle(drv, dev);
- if (entered_state > 0)
- goto exit_idle;
-
- max_latency_ns = U64_MAX;
- } else {
- max_latency_ns = dev->forced_idle_latency_limit_ns;
- }
-
- tick_nohz_idle_stop_tick();
+ if (cpuidle_paused())
+ goto default_idle;

- next_state = cpuidle_find_deepest_state(drv, dev, max_latency_ns);
- call_cpuidle(drv, dev, next_state);
+ if (dev->forced_idle_latency_limit_ns) {
+ cpuidle_deepest_state(drv, dev,
+ dev->forced_idle_latency_limit_ns);
} else {
bool stop_tick = true;

--
2.25.1