PM / devfreq: cache the last call to get_dev_status()

The return value of get_dev_status() can be reused.  Cache it so that
other parts of the kernel can reuse it instead of having to call the
same function again.

Cc: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Javi Merino <javi.merino@arm.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>

2 files changed, 33 insertions, 15 deletions

diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
index 0720ba84ca92..ae72ba5e78df 100644
--- a/drivers/devfreq/governor_simpleondemand.c
+++ b/drivers/devfreq/governor_simpleondemand.c
@@ -21,17 +21,20 @@
 static int devfreq_simple_ondemand_func(struct devfreq *df,
                                         unsigned long *freq)
 {
-        struct devfreq_dev_status stat;
-        int err = df->profile->get_dev_status(df->dev.parent, &stat);
+        int err;
+        struct devfreq_dev_status *stat;
         unsigned long long a, b;
         unsigned int dfso_upthreshold = DFSO_UPTHRESHOLD;
         unsigned int dfso_downdifferential = DFSO_DOWNDIFFERENCTIAL;
         struct devfreq_simple_ondemand_data *data = df->data;
         unsigned long max = (df->max_freq) ? df->max_freq : UINT_MAX;
 
+        err = devfreq_update_stats(df);
         if (err)
                 return err;
 
+        stat = &df->last_status;
+
         if (data) {
                 if (data->upthreshold)
                         dfso_upthreshold = data->upthreshold;
@@ -43,41 +46,41 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
                 return -EINVAL;
 
         /* Assume MAX if it is going to be divided by zero */
-        if (stat.total_time == 0) {
+        if (stat->total_time == 0) {
                 *freq = max;
                 return 0;
         }
 
         /* Prevent overflow */
-        if (stat.busy_time >= (1 << 24) || stat.total_time >= (1 << 24)) {
-                stat.busy_time >>= 7;
-                stat.total_time >>= 7;
+        if (stat->busy_time >= (1 << 24) || stat->total_time >= (1 << 24)) {
+                stat->busy_time >>= 7;
+                stat->total_time >>= 7;
         }
 
         /* Set MAX if it's busy enough */
-        if (stat.busy_time * 100 >
-            stat.total_time * dfso_upthreshold) {
+        if (stat->busy_time * 100 >
+            stat->total_time * dfso_upthreshold) {
                 *freq = max;
                 return 0;
         }
 
         /* Set MAX if we do not know the initial frequency */
-        if (stat.current_frequency == 0) {
+        if (stat->current_frequency == 0) {
                 *freq = max;
                 return 0;
         }
 
         /* Keep the current frequency */
-        if (stat.busy_time * 100 >
-            stat.total_time * (dfso_upthreshold - dfso_downdifferential)) {
-                *freq = stat.current_frequency;
+        if (stat->busy_time * 100 >
+            stat->total_time * (dfso_upthreshold - dfso_downdifferential)) {
+                *freq = stat->current_frequency;
                 return 0;
         }
 
         /* Set the desired frequency based on the load */
-        a = stat.busy_time;
-        a *= stat.current_frequency;
-        b = div_u64(a, stat.total_time);
+        a = stat->busy_time;
+        a *= stat->current_frequency;
+        b = div_u64(a, stat->total_time);
         b *= 100;
         b = div_u64(b, (dfso_upthreshold - dfso_downdifferential / 2));
         *freq = (unsigned long) b;
diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
index ce447f0f1bad..70a1c60ddda4 100644
--- a/include/linux/devfreq.h
+++ b/include/linux/devfreq.h
@@ -161,6 +161,7 @@ struct devfreq {
         struct delayed_work work;
 
         unsigned long previous_freq;
+        struct devfreq_dev_status last_status;
 
         void *data; /* private data for governors */
 
@@ -204,6 +205,15 @@ extern int devm_devfreq_register_opp_notifier(struct device *dev,
 extern void devm_devfreq_unregister_opp_notifier(struct device *dev,
                                                 struct devfreq *devfreq);
 
+/**
+ * devfreq_update_stats() - update the last_status pointer in struct devfreq
+ * @df:         the devfreq instance whose status needs updating
+ */
+static inline int devfreq_update_stats(struct devfreq *df)
+{
+        return df->profile->get_dev_status(df->dev.parent, &df->last_status);
+}
+
 #if IS_ENABLED(CONFIG_DEVFREQ_GOV_SIMPLE_ONDEMAND)
 /**
  * struct devfreq_simple_ondemand_data - void *data fed to struct devfreq
@@ -289,6 +299,11 @@ static inline void devm_devfreq_unregister_opp_notifier(struct device *dev,
                                                         struct devfreq *devfreq)
 {
 }
+
+static inline int devfreq_update_stats(struct devfreq *df)
+{
+        return -EINVAL;
+}
 #endif /* CONFIG_PM_DEVFREQ */
 
 #endif /* __LINUX_DEVFREQ_H__ */