3 files changed, 54 insertions, 34 deletions

diff --git a/drivers/cpuidle/governors/gov.h b/drivers/cpuidle/governors/gov.h
new file mode 100644
index 000000000000..99e067d9668c
--- /dev/null
+++ b/drivers/cpuidle/governors/gov.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/* Common definitions for cpuidle governors. */
+
+#ifndef __CPUIDLE_GOVERNOR_H
+#define __CPUIDLE_GOVERNOR_H
+
+/*
+ * Idle state target residency threshold used for deciding whether or not to
+ * check the time till the closest expected timer event.
+ */
+#define RESIDENCY_THRESHOLD_NS	(15 * NSEC_PER_USEC)
+
+#endif /* __CPUIDLE_GOVERNOR_H */
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index c4922684f305..b96e3da0fedd 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -19,6 +19,8 @@
 #include <linux/sched/stat.h>
 #include <linux/math64.h>
 
+#include "gov.h"
+
 #define BUCKETS 12
 #define INTERVAL_SHIFT 3
 #define INTERVALS (1UL << INTERVAL_SHIFT)
@@ -166,8 +168,7 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev);
  * of points is below a threshold. If it is... then use the
  * average of these 8 points as the estimated value.
  */
-static unsigned int get_typical_interval(struct menu_device *data,
-					 unsigned int predicted_us)
+static unsigned int get_typical_interval(struct menu_device *data)
 {
 	int i, divisor;
 	unsigned int min, max, thresh, avg;
@@ -195,11 +196,7 @@ again:
 		}
 	}
 
-	/*
-	 * If the result of the computation is going to be discarded anyway,
-	 * avoid the computation altogether.
-	 */
-	if (min >= predicted_us)
+	if (!max)
 		return UINT_MAX;
 
 	if (divisor == INTERVALS)
@@ -267,7 +264,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 {
 	struct menu_device *data = this_cpu_ptr(&menu_devices);
 	s64 latency_req = cpuidle_governor_latency_req(dev->cpu);
-	unsigned int predicted_us;
 	u64 predicted_ns;
 	u64 interactivity_req;
 	unsigned int nr_iowaiters;
@@ -279,16 +275,41 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 		data->needs_update = 0;
 	}
 
-	/* determine the expected residency time, round up */
-	delta = tick_nohz_get_sleep_length(&delta_tick);
-	if (unlikely(delta < 0)) {
-		delta = 0;
-		delta_tick = 0;
-	}
-	data->next_timer_ns = delta;
-
 	nr_iowaiters = nr_iowait_cpu(dev->cpu);
-	data->bucket = which_bucket(data->next_timer_ns, nr_iowaiters);
+
+	/* Find the shortest expected idle interval. */
+	predicted_ns = get_typical_interval(data) * NSEC_PER_USEC;
+	if (predicted_ns > RESIDENCY_THRESHOLD_NS) {
+		unsigned int timer_us;
+
+		/* Determine the time till the closest timer. */
+		delta = tick_nohz_get_sleep_length(&delta_tick);
+		if (unlikely(delta < 0)) {
+			delta = 0;
+			delta_tick = 0;
+		}
+
+		data->next_timer_ns = delta;
+		data->bucket = which_bucket(data->next_timer_ns, nr_iowaiters);
+
+		/* Round up the result for half microseconds. */
+		timer_us = div_u64((RESOLUTION * DECAY * NSEC_PER_USEC) / 2 +
+					data->next_timer_ns *
+						data->correction_factor[data->bucket],
+				   RESOLUTION * DECAY * NSEC_PER_USEC);
+		/* Use the lowest expected idle interval to pick the idle state. */
+		predicted_ns = min((u64)timer_us * NSEC_PER_USEC, predicted_ns);
+	} else {
+		/*
+		 * Because the next timer event is not going to be determined
+		 * in this case, assume that without the tick the closest timer
+		 * will be in distant future and that the closest tick will occur
+		 * after 1/2 of the tick period.
+		 */
+		data->next_timer_ns = KTIME_MAX;
+		delta_tick = TICK_NSEC / 2;
+		data->bucket = which_bucket(KTIME_MAX, nr_iowaiters);
+	}
 
 	if (unlikely(drv->state_count <= 1 || latency_req == 0) ||
 	    ((data->next_timer_ns < drv->states[1].target_residency_ns ||
@@ -303,16 +324,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 		return 0;
 	}
 
-	/* Round up the result for half microseconds. */
-	predicted_us = div_u64(data->next_timer_ns *
-			       data->correction_factor[data->bucket] +
-			       (RESOLUTION * DECAY * NSEC_PER_USEC) / 2,
-			       RESOLUTION * DECAY * NSEC_PER_USEC);
-	/* Use the lowest expected idle interval to pick the idle state. */
-	predicted_ns = (u64)min(predicted_us,
-				get_typical_interval(data, predicted_us)) *
-				NSEC_PER_USEC;
-
 	if (tick_nohz_tick_stopped()) {
 		/*
 		 * If the tick is already stopped, the cost of possible short
diff --git a/drivers/cpuidle/governors/teo.c b/drivers/cpuidle/governors/teo.c
index 70846b669255..31050fdc633f 100644
--- a/drivers/cpuidle/governors/teo.c
+++ b/drivers/cpuidle/governors/teo.c
@@ -140,6 +140,8 @@
 #include <linux/sched/topology.h>
 #include <linux/tick.h>
 
+#include "gov.h"
+
 /*
  * The number of bits to shift the CPU's capacity by in order to determine
  * the utilized threshold.
@@ -152,7 +154,6 @@
  */
 #define UTIL_THRESHOLD_SHIFT 6
 
-
 /*
  * The PULSE value is added to metrics when they grow and the DECAY_SHIFT value
  * is used for decreasing metrics on a regular basis.
@@ -166,12 +167,6 @@
  */
 #define NR_RECENT	9
 
-/*
- * Idle state target residency threshold used for deciding whether or not to
- * check the time till the closest expected timer event.
- */
-#define RESIDENCY_THRESHOLD_NS	(15 * NSEC_PER_USEC)
-
 /**
  * struct teo_bin - Metrics used by the TEO cpuidle governor.
  * @intercepts: The "intercepts" metric.