[patch 1/2] cpufreq_conservative: align codebase with ondemand for consistancy

[Alexander Clouter <alex@digriz.org.uk>]

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Something I had been meaning to do for a while.  The codebases between
ondemand and conservative have strayed and as Venkatesh has far more Clue(tm)
than I am going to adjust my code to look more like his :)

Another reason to do this is ages ago, knowingly, I did a piss poor attempt
at making conservative less responsive by knocking up
DEF_SAMPLING_RATE_LATENCY_MULTIPLIER by two orders of magnitude.  I did fix
this ages ago but in my dis-organisation I must have toasted the diff and
left it the way it was.  About two weeks ago a user contacted me saying he
was having problems with the conservative governor with his AMD Athlon XP-M
2800+ as /sys/devices/system/cpu/cpu0/cpufreq/conservative showed
  sampling_rate_min   9950000
  sampling_rate_max   1360065408

Nine seconds to decide about changing the frequency....not too responsive :)

N.B. only one bug remains, well on my machine, if anyone can see the cause 
	then let me know.  On my IBM T40p the cpu frequency only drops when 
	the mouse moves (bizarre interrupt issue?).  *Very* strange never the 
	less...

	Not using PREEMPT or DYNTICKS...any suggestions would be welcomed, no 
	one else has reported the problem though.

Signed-off-by: Alexander Clouter <alex-kernel@digriz.org.uk>

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--- linux-2.6.15/drivers/cpufreq/cpufreq_conservative.c.orig	2006-02-09 18:05:36.157782500 +0000
+++ linux-2.6.15/drivers/cpufreq/cpufreq_conservative.c	2006-02-09 19:03:35.871251000 +0000
@@ -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);
@@ -139,6 +138,9 @@
 	if (ret != 1 )
 		return -EINVAL;
 
+	if (input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
+		return -EINVAL;
+
 	down(&dbs_sem);
 	dbs_tuners_ins.sampling_down_factor = input;
 	up(&dbs_sem);
@@ -173,8 +175,7 @@
 	ret = sscanf (buf, "%u", &input);
 
 	down(&dbs_sem);
-	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) {
 		up(&dbs_sem);
 		return -EINVAL;
@@ -194,8 +195,7 @@
 	ret = sscanf (buf, "%u", &input);
 
 	down(&dbs_sem);
-	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) {
 		up(&dbs_sem);
 		return -EINVAL;
@@ -280,8 +280,8 @@
 	&sampling_rate_min.attr,
 	&sampling_rate.attr,
 	&sampling_down_factor.attr,
-	&up_threshold.attr,
 	&down_threshold.attr,
+	&up_threshold.attr,
 	&ignore_nice.attr,
 	&freq_step.attr,
 	NULL
@@ -337,7 +337,6 @@
 	 */
 
 	/* 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 +356,7 @@
 	/* 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 +397,7 @@
 		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 +414,14 @@
 	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 +436,8 @@
 		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 +508,16 @@
 		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;