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alistair23-linux/drivers/cpufreq/cpufreq_governor.h
Viresh Kumar 70f43e5e79 cpufreq: governor: replace per-CPU delayed work with timers 
cpufreq governors evaluate load at sampling rate and based on that they
update frequency for a group of CPUs belonging to the same cpufreq
policy.

This is required to be done in a single thread for all policy->cpus, but
because we don't want to wakeup idle CPUs to do just that, we use
deferrable work for this. If we would have used a single delayed
deferrable work for the entire policy, there were chances that the CPU
required to run the handler can be in idle and we might end up not
changing the frequency for the entire group with load variations.

And so we were forced to keep per-cpu works, and only the one that
expires first need to do the real work and others are rescheduled for
next sampling time.

We have been using the more complex solution until now, where we used a
delayed deferrable work for this, which is a combination of a timer and
a work.

This could be made lightweight by keeping per-cpu deferred timers with a
single work item, which is scheduled by the first timer that expires.

This patch does just that and here are important changes:
- The timer handler will run in irq context and so we need to use a
  spin_lock instead of the timer_mutex. And so a separate timer_lock is
  created. This also makes the use of the mutex and lock quite clear, as
  we know what exactly they are protecting.
- A new field 'skip_work' is added to track when the timer handlers can
  queue a work. More comments present in code.

Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-12-09 22:26:00 +01:00

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/*
* drivers/cpufreq/cpufreq_governor.h
*
* Header file for CPUFreq governors common code
*
* Copyright (C) 2001 Russell King
* (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
* (C) 2003 Jun Nakajima <jun.nakajima@intel.com>
* (C) 2009 Alexander Clouter <alex@digriz.org.uk>
* (c) 2012 Viresh Kumar <viresh.kumar@linaro.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef _CPUFREQ_GOVERNOR_H
#define _CPUFREQ_GOVERNOR_H
#include <linux/cpufreq.h>
#include <linux/kernel_stat.h>
#include <linux/module.h>
#include <linux/mutex.h>
/*
* The polling frequency depends on the capability of the processor. Default
* polling frequency is 1000 times the transition latency of the processor. The
* governor will work on any processor with transition latency <= 10ms, using
* appropriate sampling rate.
*
* For CPUs with transition latency > 10ms (mostly drivers with CPUFREQ_ETERNAL)
* this governor will not work. All times here are in us (micro seconds).
*/
#define MIN_SAMPLING_RATE_RATIO (2)
#define LATENCY_MULTIPLIER (1000)
#define MIN_LATENCY_MULTIPLIER (20)
#define TRANSITION_LATENCY_LIMIT (10 * 1000 * 1000)
/* Ondemand Sampling types */
enum {OD_NORMAL_SAMPLE, OD_SUB_SAMPLE};
/*
* Macro for creating governors sysfs routines
*
* - gov_sys: One governor instance per whole system
* - gov_pol: One governor instance per policy
*/
/* Create attributes */
#define gov_sys_attr_ro(_name) \
static struct global_attr _name##_gov_sys = \
__ATTR(_name, 0444, show_##_name##_gov_sys, NULL)
#define gov_sys_attr_rw(_name) \
static struct global_attr _name##_gov_sys = \
__ATTR(_name, 0644, show_##_name##_gov_sys, store_##_name##_gov_sys)
#define gov_pol_attr_ro(_name) \
static struct freq_attr _name##_gov_pol = \
__ATTR(_name, 0444, show_##_name##_gov_pol, NULL)
#define gov_pol_attr_rw(_name) \
static struct freq_attr _name##_gov_pol = \
__ATTR(_name, 0644, show_##_name##_gov_pol, store_##_name##_gov_pol)
#define gov_sys_pol_attr_rw(_name) \
gov_sys_attr_rw(_name); \
gov_pol_attr_rw(_name)
#define gov_sys_pol_attr_ro(_name) \
gov_sys_attr_ro(_name); \
gov_pol_attr_ro(_name)
/* Create show/store routines */
#define show_one(_gov, file_name) \
static ssize_t show_##file_name##_gov_sys \
(struct kobject *kobj, struct attribute *attr, char *buf) \
{ \
struct _gov##_dbs_tuners *tuners = _gov##_dbs_cdata.gdbs_data->tuners; \
return sprintf(buf, "%u\n", tuners->file_name); \
} \
\
static ssize_t show_##file_name##_gov_pol \
(struct cpufreq_policy *policy, char *buf) \
{ \
struct dbs_data *dbs_data = policy->governor_data; \
struct _gov##_dbs_tuners *tuners = dbs_data->tuners; \
return sprintf(buf, "%u\n", tuners->file_name); \
}
#define store_one(_gov, file_name) \
static ssize_t store_##file_name##_gov_sys \
(struct kobject *kobj, struct attribute *attr, const char *buf, size_t count) \
{ \
struct dbs_data *dbs_data = _gov##_dbs_cdata.gdbs_data; \
return store_##file_name(dbs_data, buf, count); \
} \
\
static ssize_t store_##file_name##_gov_pol \
(struct cpufreq_policy *policy, const char *buf, size_t count) \
{ \
struct dbs_data *dbs_data = policy->governor_data; \
return store_##file_name(dbs_data, buf, count); \
}
#define show_store_one(_gov, file_name) \
show_one(_gov, file_name); \
store_one(_gov, file_name)
/* create helper routines */
#define define_get_cpu_dbs_routines(_dbs_info) \
static struct cpu_dbs_info *get_cpu_cdbs(int cpu) \
{ \
return &per_cpu(_dbs_info, cpu).cdbs; \
} \
\
static void *get_cpu_dbs_info_s(int cpu) \
{ \
return &per_cpu(_dbs_info, cpu); \
}
/*
* Abbreviations:
* dbs: used as a shortform for demand based switching It helps to keep variable
* names smaller, simpler
* cdbs: common dbs
* od_*: On-demand governor
* cs_*: Conservative governor
*/
/* Common to all CPUs of a policy */
struct cpu_common_dbs_info {
struct cpufreq_policy *policy;
/*
* Per policy mutex that serializes load evaluation from limit-change
* and work-handler.
*/
struct mutex timer_mutex;
/*
* Per policy lock that serializes access to queuing work from timer
* handlers.
*/
spinlock_t timer_lock;
ktime_t time_stamp;
unsigned int skip_work;
struct work_struct work;
};
/* Per cpu structures */
struct cpu_dbs_info {
u64 prev_cpu_idle;
u64 prev_cpu_wall;
u64 prev_cpu_nice;
/*
* Used to keep track of load in the previous interval. However, when
* explicitly set to zero, it is used as a flag to ensure that we copy
* the previous load to the current interval only once, upon the first
* wake-up from idle.
*/
unsigned int prev_load;
struct timer_list timer;
struct cpu_common_dbs_info *shared;
};
struct od_cpu_dbs_info_s {
struct cpu_dbs_info cdbs;
struct cpufreq_frequency_table *freq_table;
unsigned int freq_lo;
unsigned int freq_lo_jiffies;
unsigned int freq_hi_jiffies;
unsigned int rate_mult;
unsigned int sample_type:1;
};
struct cs_cpu_dbs_info_s {
struct cpu_dbs_info cdbs;
unsigned int down_skip;
unsigned int requested_freq;
};
/* Per policy Governors sysfs tunables */
struct od_dbs_tuners {
unsigned int ignore_nice_load;
unsigned int sampling_rate;
unsigned int sampling_down_factor;
unsigned int up_threshold;
unsigned int powersave_bias;
unsigned int io_is_busy;
};
struct cs_dbs_tuners {
unsigned int ignore_nice_load;
unsigned int sampling_rate;
unsigned int sampling_down_factor;
unsigned int up_threshold;
unsigned int down_threshold;
unsigned int freq_step;
};
/* Common Governor data across policies */
struct dbs_data;
struct common_dbs_data {
/* Common across governors */
#define GOV_ONDEMAND 0
#define GOV_CONSERVATIVE 1
int governor;
struct attribute_group *attr_group_gov_sys; /* one governor - system */
struct attribute_group *attr_group_gov_pol; /* one governor - policy */
/*
* Common data for platforms that don't set
* CPUFREQ_HAVE_GOVERNOR_PER_POLICY
*/
struct dbs_data *gdbs_data;
struct cpu_dbs_info *(*get_cpu_cdbs)(int cpu);
void *(*get_cpu_dbs_info_s)(int cpu);
unsigned int (*gov_dbs_timer)(struct cpufreq_policy *policy,
bool modify_all);
void (*gov_check_cpu)(int cpu, unsigned int load);
int (*init)(struct dbs_data *dbs_data, bool notify);
void (*exit)(struct dbs_data *dbs_data, bool notify);
/* Governor specific ops, see below */
void *gov_ops;
/*
* Protects governor's data (struct dbs_data and struct common_dbs_data)
*/
struct mutex mutex;
};
/* Governor Per policy data */
struct dbs_data {
struct common_dbs_data *cdata;
unsigned int min_sampling_rate;
int usage_count;
void *tuners;
};
/* Governor specific ops, will be passed to dbs_data->gov_ops */
struct od_ops {
void (*powersave_bias_init_cpu)(int cpu);
unsigned int (*powersave_bias_target)(struct cpufreq_policy *policy,
unsigned int freq_next, unsigned int relation);
void (*freq_increase)(struct cpufreq_policy *policy, unsigned int freq);
};
static inline int delay_for_sampling_rate(unsigned int sampling_rate)
{
int delay = usecs_to_jiffies(sampling_rate);
/* We want all CPUs to do sampling nearly on same jiffy */
if (num_online_cpus() > 1)
delay -= jiffies % delay;
return delay;
}
#define declare_show_sampling_rate_min(_gov) \
static ssize_t show_sampling_rate_min_gov_sys \
(struct kobject *kobj, struct attribute *attr, char *buf) \
{ \
struct dbs_data *dbs_data = _gov##_dbs_cdata.gdbs_data; \
return sprintf(buf, "%u\n", dbs_data->min_sampling_rate); \
} \
\
static ssize_t show_sampling_rate_min_gov_pol \
(struct cpufreq_policy *policy, char *buf) \
{ \
struct dbs_data *dbs_data = policy->governor_data; \
return sprintf(buf, "%u\n", dbs_data->min_sampling_rate); \
}
extern struct mutex cpufreq_governor_lock;
void gov_add_timers(struct cpufreq_policy *policy, unsigned int delay);
void gov_cancel_work(struct cpu_common_dbs_info *shared);
void dbs_check_cpu(struct dbs_data *dbs_data, int cpu);
int cpufreq_governor_dbs(struct cpufreq_policy *policy,
struct common_dbs_data *cdata, unsigned int event);
void od_register_powersave_bias_handler(unsigned int (*f)
(struct cpufreq_policy *, unsigned int, unsigned int),
unsigned int powersave_bias);
void od_unregister_powersave_bias_handler(void);
#endif /* _CPUFREQ_GOVERNOR_H */
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