[CPUFREQ] Allow ondemand stepping to be changed by user.

Adds support so that the cpufreq change stepping is no longer fixed at 5% and
can be changed dynamically by the user

Signed-off-by: Alexander Clouter <alex-kernel@digriz.org.uk>
Signed-off-by: Dave Jones <davej@redhat.com>

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 6dc83808e5901102dae1d7aed2bb7111504a8120..0565916124674de0a4f3460897778425d122f3b9 100644 (file)
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -79,6 +79,7 @@ struct dbs_tuners {
        unsigned int            up_threshold;
        unsigned int            down_threshold;
        unsigned int            ignore_nice;
+       unsigned int            freq_step;
 };
 
 static struct dbs_tuners dbs_tuners_ins = {
@@ -117,6 +118,7 @@ show_one(sampling_down_factor, sampling_down_factor);
 show_one(up_threshold, up_threshold);
 show_one(down_threshold, down_threshold);
 show_one(ignore_nice, ignore_nice);
+show_one(freq_step, freq_step);
 
 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused, 
                const char *buf, size_t count)
@@ -235,6 +237,29 @@ static ssize_t store_ignore_nice(struct cpufreq_policy *policy,
        return count;
 }
 
+static ssize_t store_freq_step(struct cpufreq_policy *policy,
+               const char *buf, size_t count)
+{
+       unsigned int input;
+       int ret;
+
+       ret = sscanf (buf, "%u", &input);
+
+       if ( ret != 1 )
+               return -EINVAL;
+
+       if ( input > 100 )
+               input = 100;
+       
+       /* no need to test here if freq_step is zero as the user might actually
+        * want this, they would be crazy though :) */
+       down(&dbs_sem);
+       dbs_tuners_ins.freq_step = input;
+       up(&dbs_sem);
+
+       return count;
+}
+
 #define define_one_rw(_name) \
 static struct freq_attr _name = \
 __ATTR(_name, 0644, show_##_name, store_##_name)
@@ -244,6 +269,7 @@ define_one_rw(sampling_down_factor);
 define_one_rw(up_threshold);
 define_one_rw(down_threshold);
 define_one_rw(ignore_nice);
+define_one_rw(freq_step);
 
 static struct attribute * dbs_attributes[] = {
        &sampling_rate_max.attr,
@@ -253,6 +279,7 @@ static struct attribute * dbs_attributes[] = {
        &up_threshold.attr,
        &down_threshold.attr,
        &ignore_nice.attr,
+       &freq_step.attr,
        NULL
 };
 
@@ -291,7 +318,7 @@ static void dbs_check_cpu(int cpu)
         *
         * Any frequency increase takes it to the maximum frequency. 
         * Frequency reduction happens at minimum steps of 
-        * 5% of max_frequency 
+        * 5% (default) of max_frequency 
         */
 
        /* Check for frequency increase */
@@ -390,18 +417,20 @@ static void dbs_check_cpu(int cpu)
                        usecs_to_jiffies(freq_down_sampling_rate);
 
        if (idle_ticks > down_idle_ticks ) {
-               /* if we are already at the lowest speed then break out early */
-               if (policy->cur == policy->min)
+               /* if we are already at the lowest speed then break out early
+                * or if we 'cannot' reduce the speed as the user might want
+                * freq_step to be zero */
+               if (policy->cur == policy->min || dbs_tuners_ins.freq_step == 0)
                        return;
-               
-               freq_down_step = (5 * policy->max) / 100;
+
+               freq_down_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
 
                /* max freq cannot be less than 100. But who knows.... */
                if (unlikely(freq_down_step == 0))
                        freq_down_step = 5;
 
                __cpufreq_driver_target(policy,
-                       policy->cur - freq_down_step, 
+                       policy->cur - freq_down_step,
                        CPUFREQ_RELATION_H);
                return;
        }
@@ -486,6 +515,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
                                        DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
                        dbs_tuners_ins.sampling_rate = def_sampling_rate;
                        dbs_tuners_ins.ignore_nice = 0;
+                       dbs_tuners_ins.freq_step = 5;
 
                        dbs_timer_init();
                }