[CPUFREQ] ondemand governor automatic downscaling

 */

#define DEF_FREQUENCY_UP_THRESHOLD		(80)

#define MIN_FREQUENCY_UP_THRESHOLD		(0)

#define MIN_FREQUENCY_UP_THRESHOLD		(11)

#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 

 * the processor. Default polling frequency is 1000 times the transition

	unsigned int 		sampling_rate;

	unsigned int		sampling_down_factor;

	unsigned int		up_threshold;

	unsigned int		down_threshold;

	unsigned int		ignore_nice;

	unsigned int		freq_step;

};

static struct dbs_tuners dbs_tuners_ins = {

	.up_threshold 		= DEF_FREQUENCY_UP_THRESHOLD,

	.down_threshold 	= DEF_FREQUENCY_DOWN_THRESHOLD,

	.sampling_down_factor 	= DEF_SAMPLING_DOWN_FACTOR,

};

show_one(sampling_rate, sampling_rate);

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)

	down(&dbs_sem);

	if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD || 

			input < MIN_FREQUENCY_UP_THRESHOLD ||

			input <= dbs_tuners_ins.down_threshold) {

			input < MIN_FREQUENCY_UP_THRESHOLD) {

		up(&dbs_sem);

		return -EINVAL;

	}

	return count;

}

static ssize_t store_down_threshold(struct cpufreq_policy *unused, 

		const char *buf, size_t count)

{

	unsigned int input;

	int ret;

	ret = sscanf (buf, "%u", &input);

	down(&dbs_sem);

	if (ret != 1 || input > MAX_FREQUENCY_DOWN_THRESHOLD || 

			input < MIN_FREQUENCY_DOWN_THRESHOLD ||

			input >= dbs_tuners_ins.up_threshold) {

		up(&dbs_sem);

		return -EINVAL;

	}

	dbs_tuners_ins.down_threshold = input;

	up(&dbs_sem);

	return count;

}

static ssize_t store_ignore_nice(struct cpufreq_policy *policy,

		const char *buf, size_t count)

{

	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)

define_one_rw(sampling_rate);

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,

	&sampling_rate.attr,

	&sampling_down_factor.attr,

	&up_threshold.attr,

	&down_threshold.attr,

	&ignore_nice.attr,

	&freq_step.attr,

	NULL

};

static void dbs_check_cpu(int cpu)

{

	unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;

	unsigned int freq_down_step;

	unsigned int idle_ticks, up_idle_ticks, total_ticks;

	unsigned int freq_next;

	unsigned int freq_down_sampling_rate;

	static int down_skip[NR_CPUS];

	struct cpu_dbs_info_s *this_dbs_info;

	policy = this_dbs_info->cur_policy;

	/* 

	 * The default safe range is 20% to 80% 

	 * Every sampling_rate, we check

	 * 	- If current idle time is less than 20%, then we try to 

	 * 	  increase frequency

	 * Every sampling_rate*sampling_down_factor, we check

	 * 	- If current idle time is more than 80%, then we try to

	 * 	  decrease frequency

	 * Every sampling_rate, we check, if current idle time is less

	 * than 20% (default), then we try to increase frequency

	 * Every sampling_rate*sampling_down_factor, we look for a the lowest

	 * frequency which can sustain the load while keeping idle time over

	 * 30%. If such a frequency exist, we try to decrease to this frequency.

	 *

	 * Any frequency increase takes it to the maximum frequency. 

	 * Frequency reduction happens at minimum steps of 

	 * 5% (default) of max_frequency 

	 * 5% (default) of current frequency 

	 */

	/* Check for frequency increase */

			idle_ticks = tmp_idle_ticks;

	}

	/* Scale idle ticks by 100 and compare with up and down ticks */

	idle_ticks *= 100;

	down_skip[cpu] = 0;

	/* if we cannot reduce the frequency anymore, break out early */

	if (policy->cur == policy->min)

		return;

	/* Compute how many ticks there are between two measurements */

	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);

	if (idle_ticks > down_idle_ticks) {

		/* 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 = (dbs_tuners_ins.freq_step * policy->max) / 100;

	total_ticks = usecs_to_jiffies(freq_down_sampling_rate);

		/* max freq cannot be less than 100. But who knows.... */

		if (unlikely(freq_down_step == 0))

			freq_down_step = 5;

	/*

	 * The optimal frequency is the frequency that is the lowest that

	 * can support the current CPU usage without triggering the up

	 * policy. To be safe, we focus 10 points under the threshold.

	 */

	freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks;

	freq_next = (freq_next * policy->cur) / 

			(dbs_tuners_ins.up_threshold - 10);

		__cpufreq_driver_target(policy,

			policy->cur - freq_down_step,

			CPUFREQ_RELATION_H);

		return;

	}

	if (freq_next <= ((policy->cur * 95) / 100))

		__cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L);

}

static void do_dbs_timer(void *data)

					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();

		}