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

From: Ulf Hansson <ulf.hansson@linaro.org>
To: "Rafael J . Wysocki" <rafael@kernel.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	linux-pm@vger.kernel.org
Cc: Maulik Shah <mkshah@codeaurora.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Len Brown <len.brown@intel.com>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH 1/2] cpuidle: Avoid calls to cpuidle_resume|pause() for s2idle
Date: Wed, 29 Sep 2021 16:44:50 +0200	[thread overview]
Message-ID: <20210929144451.113334-2-ulf.hansson@linaro.org> (raw)
In-Reply-To: <20210929144451.113334-1-ulf.hansson@linaro.org>

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

