cpuidle: governors: Consolidate PM QoS handling

There is some code duplication related to the PM QoS handling between
the existing cpuidle governors, so move that code to a common helper
function and call that from the governors.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpuidle/governor.c

@@ -8,8 +8,10 @@
  * This code is licenced under the GPL.
  */
 
-#include <linux/mutex.h>
+#include <linux/cpu.h>
 #include <linux/cpuidle.h>
+#include <linux/mutex.h>
+#include <linux/pm_qos.h>
 
 #include "cpuidle.h"
 
@@ -93,3 +95,16 @@ int cpuidle_register_governor(struct cpuidle_governor *gov)
 
 	return ret;
 }
+
+/**
+ * cpuidle_governor_latency_req - Compute a latency constraint for CPU
+ * @cpu: Target CPU
+ */
+int cpuidle_governor_latency_req(unsigned int cpu)
+{
+	int global_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
+	struct device *device = get_cpu_device(cpu);
+	int device_req = dev_pm_qos_raw_read_value(device);
+
+	return device_req < global_req ? device_req : global_req;
+}

drivers/cpuidle/governors/ladder.c

@@ -14,10 +14,8 @@
 
 #include <linux/kernel.h>
 #include <linux/cpuidle.h>
-#include <linux/pm_qos.h>
 #include <linux/jiffies.h>
 #include <linux/tick.h>
-#include <linux/cpu.h>
 
 #include <asm/io.h>
 #include <linux/uaccess.h>
@@ -69,15 +67,10 @@ static int ladder_select_state(struct cpuidle_driver *drv,
 			       struct cpuidle_device *dev, bool *dummy)
 {
 	struct ladder_device *ldev = this_cpu_ptr(&ladder_devices);
-	struct device *device = get_cpu_device(dev->cpu);
 	struct ladder_device_state *last_state;
 	int last_residency, last_idx = ldev->last_state_idx;
 	int first_idx = drv->states[0].flags & CPUIDLE_FLAG_POLLING ? 1 : 0;
-	int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
-	int resume_latency = dev_pm_qos_raw_read_value(device);
-
-	if (resume_latency < latency_req)
-		latency_req = resume_latency;
+	int latency_req = cpuidle_governor_latency_req(dev->cpu);
 
 	/* Special case when user has set very strict latency requirement */
 	if (unlikely(latency_req == 0)) {

drivers/cpuidle/governors/menu.c

@@ -12,7 +12,6 @@
 
 #include <linux/kernel.h>
 #include <linux/cpuidle.h>
-#include <linux/pm_qos.h>
 #include <linux/time.h>
 #include <linux/ktime.h>
 #include <linux/hrtimer.h>
@@ -21,7 +20,6 @@
 #include <linux/sched/loadavg.h>
 #include <linux/sched/stat.h>
 #include <linux/math64.h>
-#include <linux/cpu.h>
 
 /*
  * Please note when changing the tuning values:
@@ -286,15 +284,13 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 		       bool *stop_tick)
 {
 	struct menu_device *data = this_cpu_ptr(&menu_devices);
-	struct device *device = get_cpu_device(dev->cpu);
-	int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
+	int latency_req = cpuidle_governor_latency_req(dev->cpu);
 	int i;
 	int first_idx;
 	int idx;
 	unsigned int interactivity_req;
 	unsigned int expected_interval;
 	unsigned long nr_iowaiters, cpu_load;
-	int resume_latency = dev_pm_qos_raw_read_value(device);
 	ktime_t delta_next;
 
 	if (data->needs_update) {
@@ -302,9 +298,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 		data->needs_update = 0;
 	}
 
-	if (resume_latency < latency_req)
-		latency_req = resume_latency;
-
 	/* Special case when user has set very strict latency requirement */
 	if (unlikely(latency_req == 0)) {
 		*stop_tick = false;

include/linux/cpuidle.h

@@ -258,6 +258,7 @@ struct cpuidle_governor {
 
 #ifdef CONFIG_CPU_IDLE
 extern int cpuidle_register_governor(struct cpuidle_governor *gov);
+extern int cpuidle_governor_latency_req(unsigned int cpu);
 #else
 static inline int cpuidle_register_governor(struct cpuidle_governor *gov)
 {return 0;}