cpuidle: Pass exit latency limit to cpuidle_use_deepest_state()

Modify cpuidle_use_deepest_state() to take an additional exit latency
limit argument to be passed to find_deepest_idle_state() and make
cpuidle_idle_call() pass dev->forced_idle_latency_limit_ns to it for
forced idle.
Suggested-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
[ rjw: Rebase and rearrange code, subject & changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpuidle/cpuidle.c

@@ -123,9 +123,10 @@ void cpuidle_use_deepest_state(u64 latency_limit_ns)
  * @dev: cpuidle device for the given CPU.
  */
 int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
-			       struct cpuidle_device *dev)
+			       struct cpuidle_device *dev,
+			       u64 latency_limit_ns)
 {
-	return find_deepest_state(drv, dev, U64_MAX, 0, false);
+	return find_deepest_state(drv, dev, latency_limit_ns, 0, false);
 }
 
 #ifdef CONFIG_SUSPEND

include/linux/cpuidle.h

@@ -213,13 +213,15 @@ static inline struct cpuidle_device *cpuidle_get_device(void) {return NULL; }
 
 #ifdef CONFIG_CPU_IDLE
 extern int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
-				      struct cpuidle_device *dev);
+				      struct cpuidle_device *dev,
+				      u64 latency_limit_ns);
 extern int cpuidle_enter_s2idle(struct cpuidle_driver *drv,
 				struct cpuidle_device *dev);
 extern void cpuidle_use_deepest_state(u64 latency_limit_ns);
 #else
 static inline int cpuidle_find_deepest_state(struct cpuidle_driver *drv,
-					     struct cpuidle_device *dev)
+					     struct cpuidle_device *dev,
+					     u64 latency_limit_ns)
 {return -ENODEV; }
 static inline int cpuidle_enter_s2idle(struct cpuidle_driver *drv,
 				       struct cpuidle_device *dev)

kernel/sched/idle.c

@@ -166,6 +166,8 @@ static void cpuidle_idle_call(void)
 	 */
 
 	if (idle_should_enter_s2idle() || dev->forced_idle_latency_limit_ns) {
+		u64 max_latency_ns;
+
 		if (idle_should_enter_s2idle()) {
 			rcu_idle_enter();
 
@@ -176,12 +178,16 @@ static void cpuidle_idle_call(void)
 			}
 
 			rcu_idle_exit();
+
+			max_latency_ns = U64_MAX;
+		} else {
+			max_latency_ns = dev->forced_idle_latency_limit_ns;
 		}
 
 		tick_nohz_idle_stop_tick();
 		rcu_idle_enter();
 
-		next_state = cpuidle_find_deepest_state(drv, dev);
+		next_state = cpuidle_find_deepest_state(drv, dev, max_latency_ns);
 		call_cpuidle(drv, dev, next_state);
 	} else {
 		bool stop_tick = true;