1 files changed, 27 insertions, 26 deletions

diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c
index ac38766b2583..adecd31f6156 100644
--- a/drivers/cpufreq/cpufreq_conservative.c
+++ b/drivers/cpufreq/cpufreq_conservative.c
@@ -35,12 +35,7 @@
  */
 
 #define DEF_FREQUENCY_UP_THRESHOLD              (80)
-#define MIN_FREQUENCY_UP_THRESHOLD              (0)
-#define MAX_FREQUENCY_UP_THRESHOLD              (100)
-
 #define DEF_FREQUENCY_DOWN_THRESHOLD            (20)
-#define MIN_FREQUENCY_DOWN_THRESHOLD            (0)
-#define MAX_FREQUENCY_DOWN_THRESHOLD            (100)
 
 /* 
  * The polling frequency of this governor depends on the capability of 
@@ -53,10 +48,14 @@
  * All times here are in uS.
  */
 static unsigned int                             def_sampling_rate;
-#define MIN_SAMPLING_RATE                       (def_sampling_rate / 2)
+#define MIN_SAMPLING_RATE_RATIO                 (2)
+/* for correct statistics, we need at least 10 ticks between each measure */
+#define MIN_STAT_SAMPLING_RATE                  (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
+#define MIN_SAMPLING_RATE                       (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
 #define MAX_SAMPLING_RATE                       (500 * def_sampling_rate)
-#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (100000)
-#define DEF_SAMPLING_DOWN_FACTOR                (5)
+#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER    (1000)
+#define DEF_SAMPLING_DOWN_FACTOR                (1)
+#define MAX_SAMPLING_DOWN_FACTOR                (10)
 #define TRANSITION_LATENCY_LIMIT                (10 * 1000)
 
 static void do_dbs_timer(void *data);
@@ -136,7 +135,7 @@ static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
         unsigned int input;
         int ret;
         ret = sscanf (buf, "%u", &input);
-        if (ret != 1 )
+        if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
                 return -EINVAL;
 
         mutex_lock(&dbs_mutex);
@@ -173,8 +172,7 @@ static ssize_t store_up_threshold(struct cpufreq_policy *unused,
         ret = sscanf (buf, "%u", &input);
 
         mutex_lock(&dbs_mutex);
-        if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD || 
-                        input < MIN_FREQUENCY_UP_THRESHOLD ||
+        if (ret != 1 || input > 100 || input < 0 ||
                         input <= dbs_tuners_ins.down_threshold) {
                 mutex_unlock(&dbs_mutex);
                 return -EINVAL;
@@ -194,8 +192,7 @@ static ssize_t store_down_threshold(struct cpufreq_policy *unused,
         ret = sscanf (buf, "%u", &input);
 
         mutex_lock(&dbs_mutex);
-        if (ret != 1 || input > MAX_FREQUENCY_DOWN_THRESHOLD || 
-                        input < MIN_FREQUENCY_DOWN_THRESHOLD ||
+        if (ret != 1 || input > 100 || input < 0 ||
                         input >= dbs_tuners_ins.up_threshold) {
                 mutex_unlock(&dbs_mutex);
                 return -EINVAL;
@@ -337,7 +334,6 @@ static void dbs_check_cpu(int cpu)
          */
 
         /* Check for frequency increase */
-
         idle_ticks = UINT_MAX;
         for_each_cpu_mask(j, policy->cpus) {
                 unsigned int tmp_idle_ticks, total_idle_ticks;
@@ -357,7 +353,7 @@ static void dbs_check_cpu(int cpu)
         /* Scale idle ticks by 100 and compare with up and down ticks */
         idle_ticks *= 100;
         up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
-                usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
+                        usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 
         if (idle_ticks < up_idle_ticks) {
                 down_skip[cpu] = 0;
@@ -398,6 +394,7 @@ static void dbs_check_cpu(int cpu)
                 struct cpu_dbs_info_s *j_dbs_info;
 
                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
+                /* Check for frequency decrease */
                 total_idle_ticks = j_dbs_info->prev_cpu_idle_up;
                 tmp_idle_ticks = total_idle_ticks -
                         j_dbs_info->prev_cpu_idle_down;
@@ -414,12 +411,14 @@ static void dbs_check_cpu(int cpu)
         freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
                 dbs_tuners_ins.sampling_down_factor;
         down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) *
-                        usecs_to_jiffies(freq_down_sampling_rate);
+                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 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 */
+                 * freq_step to be zero
+                 */
                 if (requested_freq[cpu] == policy->min
                                 || dbs_tuners_ins.freq_step == 0)
                         return;
@@ -434,9 +433,8 @@ static void dbs_check_cpu(int cpu)
                 if (requested_freq[cpu] < policy->min)
                         requested_freq[cpu] = policy->min;
 
-                __cpufreq_driver_target(policy,
-                        requested_freq[cpu],
-                        CPUFREQ_RELATION_H);
+                __cpufreq_driver_target(policy, requested_freq[cpu],
+                                CPUFREQ_RELATION_H);
                 return;
         }
 }
@@ -507,13 +505,16 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
                 if (dbs_enable == 1) {
                         unsigned int latency;
                         /* policy latency is in nS. Convert it to uS first */
+                        latency = policy->cpuinfo.transition_latency / 1000;
+                        if (latency == 0)
+                                latency = 1;
 
-                        latency = policy->cpuinfo.transition_latency;
-                        if (latency < 1000)
-                                latency = 1000;
-
-                        def_sampling_rate = (latency / 1000) *
+                        def_sampling_rate = latency *
                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
+
+                        if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
+                                def_sampling_rate = MIN_STAT_SAMPLING_RATE;
+
                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
                         dbs_tuners_ins.ignore_nice = 0;
                         dbs_tuners_ins.freq_step = 5;