cpufreq: ondemand: Replace down_differential tuner with adj_up_threshold

In order to avoid the calculation of up_threshold - down_differential
every time that the frequency must be decreased, we replace the
down_differential tuner with the adj_up_threshold which keeps the
difference across multiple checks.

Update the adj_up_threshold only when the up_theshold is also updated.

Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 11 insertions, 7 deletions

diff --git a/drivers/cpufreq/cpufreq_governor.h b/drivers/cpufreq/cpufreq_governor.h
index 16314b65ca67..d2ac91150600 100644
--- a/drivers/cpufreq/cpufreq_governor.h
+++ b/drivers/cpufreq/cpufreq_governor.h
@@ -109,7 +109,7 @@ struct od_dbs_tuners {
         unsigned int sampling_rate;
         unsigned int sampling_down_factor;
         unsigned int up_threshold;
-        unsigned int down_differential;
+        unsigned int adj_up_threshold;
         unsigned int powersave_bias;
         unsigned int io_is_busy;
 };
diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index f38b8da60128..09b27ae6576f 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -47,7 +47,8 @@ static struct cpufreq_governor cpufreq_gov_ondemand;
 static struct od_dbs_tuners od_tuners = {
         .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
         .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR,
-        .down_differential = DEF_FREQUENCY_DOWN_DIFFERENTIAL,
+        .adj_up_threshold = DEF_FREQUENCY_UP_THRESHOLD -
+                            DEF_FREQUENCY_DOWN_DIFFERENTIAL,
         .ignore_nice = 0,
         .powersave_bias = 0,
 };
@@ -192,11 +193,9 @@ static void od_check_cpu(int cpu, unsigned int load_freq)
          * support the current CPU usage without triggering the up policy. To be
          * safe, we focus 10 points under the threshold.
          */
-        if (load_freq < (od_tuners.up_threshold - od_tuners.down_differential) *
-                        policy->cur) {
+        if (load_freq < od_tuners.adj_up_threshold * policy->cur) {
                 unsigned int freq_next;
-                freq_next = load_freq / (od_tuners.up_threshold -
-                                od_tuners.down_differential);
+                freq_next = load_freq / od_tuners.adj_up_threshold;
 
                 /* No longer fully busy, reset rate_mult */
                 dbs_info->rate_mult = 1;
@@ -359,6 +358,10 @@ static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
                         input < MIN_FREQUENCY_UP_THRESHOLD) {
                 return -EINVAL;
         }
+        /* Calculate the new adj_up_threshold */
+        od_tuners.adj_up_threshold += input;
+        od_tuners.adj_up_threshold -= od_tuners.up_threshold;
+
         od_tuners.up_threshold = input;
         return count;
 }
@@ -515,7 +518,8 @@ static int __init cpufreq_gov_dbs_init(void)
         if (idle_time != -1ULL) {
                 /* Idle micro accounting is supported. Use finer thresholds */
                 od_tuners.up_threshold = MICRO_FREQUENCY_UP_THRESHOLD;
-                od_tuners.down_differential = MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
+                od_tuners.adj_up_threshold = MICRO_FREQUENCY_UP_THRESHOLD -
+                                             MICRO_FREQUENCY_DOWN_DIFFERENTIAL;
                 /*
                  * In nohz/micro accounting case we set the minimum frequency
                  * not depending on HZ, but fixed (very low). The deferred