text: /*
   * CPUFreq governor based on scheduler-provided CPU utilization data.
   *
   * Copyright (C) 2016, Intel Corporation
   * Author: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
   *
   * 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.
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/cpufreq.h>
  #include <linux/kthread.h>
  #include <uapi/linux/sched/types.h>
  #include <linux/slab.h>
  #include <trace/events/power.h>
  
  #include "sched.h"
  
  #define SUGOV_KTHREAD_PRIORITY	50
  
  struct sugov_tunables {
  	struct gov_attr_set attr_set;
  	unsigned int rate_limit_us;
  };
  
  struct sugov_policy {
  	struct cpufreq_policy *policy;
  
  	struct sugov_tunables *tunables;
  	struct list_head tunables_hook;
  
  	raw_spinlock_t update_lock;  /* For shared policies */
  	u64 last_freq_update_time;
  	s64 freq_update_delay_ns;
  	unsigned int next_freq;
  	unsigned int cached_raw_freq;
  
  	/* The next fields are only needed if fast switch cannot be used. */
  	struct irq_work irq_work;
  	struct kthread_work work;
  	struct mutex work_lock;
  	struct kthread_worker worker;
  	struct task_struct *thread;
  	bool work_in_progress;
  
  	bool need_freq_update;
  };
  
  struct sugov_cpu {
  	struct update_util_data update_util;
  	struct sugov_policy *sg_policy;
  
  	unsigned long iowait_boost;
  	unsigned long iowait_boost_max;
  	u64 last_update;
  
  	/* The fields below are only needed when sharing a policy. */
  	unsigned long util;
  	unsigned long max;
  	unsigned int flags;
  };
  
  static DEFINE_PER_CPU(struct sugov_cpu, sugov_cpu);
  
  /************************ Governor internals ***********************/
  
  static bool sugov_should_update_freq(struct sugov_policy *sg_policy, u64 time)
  {
  	s64 delta_ns;
  
  	if (sg_policy->work_in_progress)
  		return false;
  
  	if (unlikely(sg_policy->need_freq_update)) {
  		sg_policy->need_freq_update = false;
  		/*
  		 * This happens when limits change, so forget the previous
  		 * next_freq value and force an update.
  		 */
  		sg_policy->next_freq = UINT_MAX;
  		return true;
  	}
  
  	delta_ns = time - sg_policy->last_freq_update_time;
  	return delta_ns >= sg_policy->freq_update_delay_ns;
  }
  
  static void sugov_update_commit(struct sugov_policy *sg_policy, u64 time,
  				unsigned int next_freq)
  {
  	struct cpufreq_policy *policy = sg_policy->policy;
  
  	sg_policy->last_freq_update_time = time;
  
  	if (policy->fast_switch_enabled) {
  		if (sg_policy->next_freq == next_freq) {
  			trace_cpu_frequency(policy->cur, smp_processor_id());
  			return;
  		}
  		sg_policy->next_freq = next_freq;
  		next_freq = cpufreq_driver_fast_switch(policy, next_freq);
  		if (next_freq == CPUFREQ_ENTRY_INVALID)
  			return;
  
  		policy->cur = next_freq;
  		trace_cpu_frequency(next_freq, smp_processor_id());
  	} else if (sg_policy->next_freq != next_freq) {
  		sg_policy->next_freq = next_freq;
  		sg_policy->work_in_progress = true;
  		irq_work_queue(&sg_policy->irq_work);
  	}
  }
  
  /**
   * get_next_freq - Compute a new frequency for a given cpufreq policy.
   * @sg_policy: schedutil policy object to compute the new frequency for.
   * @util: Current CPU utilization.
   * @max: CPU capacity.
   *
   * If the utilization is frequency-invariant, choose the new frequency to be
   * proportional to it, that is
   *
   * next_freq = C * max_freq * util / max
   *
   * Otherwise, approximate the would-be frequency-invariant utilization by
   * util_raw * (curr_freq / max_freq) which leads to
   *
   * next_freq = C * curr_freq * util_raw / max
   *
   * Take C = 1.25 for the frequency tipping point at (util / max) = 0.8.
   *
   * The lowest driver-supported frequency which is equal or greater than the raw
   * next_freq (as calculated above) is returned, subject to policy min/max and
   * cpufreq driver limitations.
   */
  static unsigned int get_next_freq(struct sugov_policy *sg_policy,
  				  unsigned long util, unsigned long max)
  {
  	struct cpufreq_policy *policy = sg_policy->policy;
  	unsigned int freq = arch_scale_freq_invariant() ?
  				policy->cpuinfo.max_freq : policy->cur;
  
  	freq = (freq + (freq >> 2)) * util / max;
  
  	if (freq == sg_policy->cached_raw_freq && sg_policy->next_freq != UINT_MAX)
  		return sg_policy->next_freq;
  	sg_policy->cached_raw_freq = freq;
  	return cpufreq_driver_resolve_freq(policy, freq);
  }
  
  static void sugov_get_util(unsigned long *util, unsigned long *max)
  {
  	struct rq *rq = this_rq();
  	unsigned long cfs_max;
  
  	cfs_max = arch_scale_cpu_capacity(NULL, smp_processor_id());
  
  	*util = min(rq->cfs.avg.util_avg, cfs_max);
  	*max = cfs_max;
  }
  
  static void sugov_set_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
  				   unsigned int flags)
  {
  	if (flags & SCHED_CPUFREQ_IOWAIT) {
  		sg_cpu->iowait_boost = sg_cpu->iowait_boost_max;
  	} else if (sg_cpu->iowait_boost) {
  		s64 delta_ns = time - sg_cpu->last_update;
  
  		/* Clear iowait_boost if the CPU apprears to have been idle. */
  		if (delta_ns > TICK_NSEC)
  			sg_cpu->iowait_boost = 0;
  	}
  }
  
  static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, unsigned long *util,
  			       unsigned long *max)
  {
  	unsigned long boost_util = sg_cpu->iowait_boost;
  	unsigned long boost_max = sg_cpu->iowait_boost_max;
  
  	if (!boost_util)
  		return;
  
  	if (*util * boost_max < *max * boost_util) {
  		*util = boost_util;
  		*max = boost_max;
  	}
  	sg_cpu->iowait_boost >>= 1;
  }
  
  static void sugov_update_single(struct update_util_data *hook, u64 time,
  				unsigned int flags)
  {
  	struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
  	struct sugov_policy *sg_policy = sg_cpu->sg_policy;
  	struct cpufreq_policy *policy = sg_policy->policy;
  	unsigned long util, max;
  	unsigned int next_f;
  
  	sugov_set_iowait_boost(sg_cpu, time, flags);
  	sg_cpu->last_update = time;
  
  	if (!sugov_should_update_freq(sg_policy, time))
  		return;
  
  	if (flags & SCHED_CPUFREQ_RT_DL) {
  		next_f = policy->cpuinfo.max_freq;
  	} else {
  		sugov_get_util(&util, &max);
  		sugov_iowait_boost(sg_cpu, &util, &max);
  		next_f = get_next_freq(sg_policy, util, max);
  	}
  	sugov_update_commit(sg_policy, time, next_f);
  }
  
  static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu,
  					   unsigned long util, unsigned long max,
  					   unsigned int flags)
  {
  	struct sugov_policy *sg_policy = sg_cpu->sg_policy;
  	struct cpufreq_policy *policy = sg_policy->policy;
  	unsigned int max_f = policy->cpuinfo.max_freq;
  	u64 last_freq_update_time = sg_policy->last_freq_update_time;
  	unsigned int j;
  
  	if (flags & SCHED_CPUFREQ_RT_DL)
  		return max_f;
  
  	sugov_iowait_boost(sg_cpu, &util, &max);
  
  	for_each_cpu(j, policy->cpus) {
  		struct sugov_cpu *j_sg_cpu;
  		unsigned long j_util, j_max;
  		s64 delta_ns;
  
  		if (j == smp_processor_id())
  			continue;
  
  		j_sg_cpu = &per_cpu(sugov_cpu, j);
  		/*
  		 * If the CPU utilization was last updated before the previous
  		 * frequency update and the time elapsed between the last update
  		 * of the CPU utilization and the last frequency update is long
  		 * enough, don't take the CPU into account as it probably is
  		 * idle now (and clear iowait_boost for it).
  		 */
  		delta_ns = last_freq_update_time - j_sg_cpu->last_update;
  		if (delta_ns > TICK_NSEC) {
  			j_sg_cpu->iowait_boost = 0;
  			continue;
  		}
  		if (j_sg_cpu->flags & SCHED_CPUFREQ_RT_DL)
  			return max_f;
  
  		j_util = j_sg_cpu->util;
  		j_max = j_sg_cpu->max;
  		if (j_util * max > j_max * util) {
  			util = j_util;
  			max = j_max;
  		}
  
  		sugov_iowait_boost(j_sg_cpu, &util, &max);
  	}
  
  	return get_next_freq(sg_policy, util, max);
  }
  
  static void sugov_update_shared(struct update_util_data *hook, u64 time,
  				unsigned int flags)
  {
  	struct sugov_cpu *sg_cpu = container_of(hook, struct sugov_cpu, update_util);
  	struct sugov_policy *sg_policy = sg_cpu->sg_policy;
  	unsigned long util, max;
  	unsigned int next_f;
  
  	sugov_get_util(&util, &max);
  
  	raw_spin_lock(&sg_policy->update_lock);
  
  	sg_cpu->util = util;
  	sg_cpu->max = max;
  	sg_cpu->flags = flags;
  
  	sugov_set_iowait_boost(sg_cpu, time, flags);
  	sg_cpu->last_update = time;
  
  	if (sugov_should_update_freq(sg_policy, time)) {
  		next_f = sugov_next_freq_shared(sg_cpu, util, max, flags);
  		sugov_update_commit(sg_policy, time, next_f);
  	}
  
  	raw_spin_unlock(&sg_policy->update_lock);
  }
  
  static void sugov_work(struct kthread_work *work)
  {
  	struct sugov_policy *sg_policy = container_of(work, struct sugov_policy, work);
  
  	mutex_lock(&sg_policy->work_lock);
  	__cpufreq_driver_target(sg_policy->policy, sg_policy->next_freq,
  				CPUFREQ_RELATION_L);
  	mutex_unlock(&sg_policy->work_lock);
  
  	sg_policy->work_in_progress = false;
  }
  
  static void sugov_irq_work(struct irq_work *irq_work)
  {
  	struct sugov_policy *sg_policy;
  
  	sg_policy = container_of(irq_work, struct sugov_policy, irq_work);
  
  	/*
  	 * For RT and deadline tasks, the schedutil governor shoots the
  	 * frequency to maximum. Special care must be taken to ensure that this
  	 * kthread doesn't result in the same behavior.
  	 *
  	 * This is (mostly) guaranteed by the work_in_progress flag. The flag is
  	 * updated only at the end of the sugov_work() function and before that
  	 * the schedutil governor rejects all other frequency scaling requests.
  	 *
  	 * There is a very rare case though, where the RT thread yields right
  	 * after the work_in_progress flag is cleared. The effects of that are
  	 * neglected for now.
  	 */
  	kthread_queue_work(&sg_policy->worker, &sg_policy->work);
  }
  
  /************************** sysfs interface ************************/
  
  static struct sugov_tunables *global_tunables;
  static DEFINE_MUTEX(global_tunables_lock);
  
  static inline struct sugov_tunables *to_sugov_tunables(struct gov_attr_set *attr_set)
  {
  	return container_of(attr_set, struct sugov_tunables, attr_set);
  }
  
  static ssize_t rate_limit_us_show(struct gov_attr_set *attr_set, char *buf)
  {
  	struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
  
  	return sprintf(buf, "%u\n", tunables->rate_limit_us);
  }
  
  static ssize_t rate_limit_us_store(struct gov_attr_set *attr_set, const char *buf,
  				   size_t count)
  {
  	struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
  	struct sugov_policy *sg_policy;
  	unsigned int rate_limit_us;
  
  	if (kstrtouint(buf, 10, &rate_limit_us))
  		return -EINVAL;
  
  	tunables->rate_limit_us = rate_limit_us;
  
  	list_for_each_entry(sg_policy, &attr_set->policy_list, tunables_hook)
  		sg_policy->freq_update_delay_ns = rate_limit_us * NSEC_PER_USEC;
  
  	return count;
  }
  
  static struct governor_attr rate_limit_us = __ATTR_RW(rate_limit_us);
  
  static struct attribute *sugov_attributes[] = {
  	&rate_limit_us.attr,
  	NULL
  };
  
  static struct kobj_type sugov_tunables_ktype = {
  	.default_attrs = sugov_attributes,
  	.sysfs_ops = &governor_sysfs_ops,
  };
  
  /********************** cpufreq governor interface *********************/
  
  static struct cpufreq_governor schedutil_gov;
  
  static struct sugov_policy *sugov_policy_alloc(struct cpufreq_policy *policy)
  {
  	struct sugov_policy *sg_policy;
  
  	sg_policy = kzalloc(sizeof(*sg_policy), GFP_KERNEL);
  	if (!sg_policy)
  		return NULL;
  
  	sg_policy->policy = policy;
  	raw_spin_lock_init(&sg_policy->update_lock);
  	return sg_policy;
  }
  
  static void sugov_policy_free(struct sugov_policy *sg_policy)
  {
  	kfree(sg_policy);
  }
  
  static int sugov_kthread_create(struct sugov_policy *sg_policy)
  {
  	struct task_struct *thread;
  	struct sched_param param = { .sched_priority = MAX_USER_RT_PRIO / 2 };
  	struct cpufreq_policy *policy = sg_policy->policy;
  	int ret;
  
  	/* kthread only required for slow path */
  	if (policy->fast_switch_enabled)
  		return 0;
  
  	kthread_init_work(&sg_policy->work, sugov_work);
  	kthread_init_worker(&sg_policy->worker);
  	thread = kthread_create(kthread_worker_fn, &sg_policy->worker,
  				"sugov:%d",
  				cpumask_first(policy->related_cpus));
  	if (IS_ERR(thread)) {
  		pr_err("failed to create sugov thread: %ld\n", PTR_ERR(thread));
  		return PTR_ERR(thread);
  	}
  
  	ret = sched_setscheduler_nocheck(thread, SCHED_FIFO, &param);
  	if (ret) {
  		kthread_stop(thread);
  		pr_warn("%s: failed to set SCHED_FIFO\n", __func__);
  		return ret;
  	}
  
  	sg_policy->thread = thread;
  	kthread_bind_mask(thread, policy->related_cpus);
  	init_irq_work(&sg_policy->irq_work, sugov_irq_work);
  	mutex_init(&sg_policy->work_lock);
  
  	wake_up_process(thread);
  
  	return 0;
  }
  
  static void sugov_kthread_stop(struct sugov_policy *sg_policy)
  {
  	/* kthread only required for slow path */
  	if (sg_policy->policy->fast_switch_enabled)
  		return;
  
  	kthread_flush_worker(&sg_policy->worker);
  	kthread_stop(sg_policy->thread);
  	mutex_destroy(&sg_policy->work_lock);
  }
  
  static struct sugov_tunables *sugov_tunables_alloc(struct sugov_policy *sg_policy)
  {
  	struct sugov_tunables *tunables;
  
  	tunables = kzalloc(sizeof(*tunables), GFP_KERNEL);
  	if (tunables) {
  		gov_attr_set_init(&tunables->attr_set, &sg_policy->tunables_hook);
  		if (!have_governor_per_policy())
  			global_tunables = tunables;
  	}
  	return tunables;
  }
  
  static void sugov_tunables_free(struct sugov_tunables *tunables)
  {
  	if (!have_governor_per_policy())
  		global_tunables = NULL;
  
  	kfree(tunables);
  }
  
  static int sugov_init(struct cpufreq_policy *policy)
  {
  	struct sugov_policy *sg_policy;
  	struct sugov_tunables *tunables;
  	unsigned int lat;
  	int ret = 0;
  
  	/* State should be equivalent to EXIT */
  	if (policy->governor_data)
  		return -EBUSY;
  
  	cpufreq_enable_fast_switch(policy);
  
  	sg_policy = sugov_policy_alloc(policy);
  	if (!sg_policy) {
  		ret = -ENOMEM;
  		goto disable_fast_switch;
  	}
  
  	ret = sugov_kthread_create(sg_policy);
  	if (ret)
  		goto free_sg_policy;
  
  	mutex_lock(&global_tunables_lock);
  
  	if (global_tunables) {
  		if (WARN_ON(have_governor_per_policy())) {
  			ret = -EINVAL;
  			goto stop_kthread;
  		}
  		policy->governor_data = sg_policy;
  		sg_policy->tunables = global_tunables;
  
  		gov_attr_set_get(&global_tunables->attr_set, &sg_policy->tunables_hook);
  		goto out;
  	}
  
  	tunables = sugov_tunables_alloc(sg_policy);
  	if (!tunables) {
  		ret = -ENOMEM;
  		goto stop_kthread;
  	}
  
  	tunables->rate_limit_us = LATENCY_MULTIPLIER;
  	lat = policy->cpuinfo.transition_latency / NSEC_PER_USEC;
  	if (lat)
  		tunables->rate_limit_us *= lat;
  
  	policy->governor_data = sg_policy;
  	sg_policy->tunables = tunables;
  
  	ret = kobject_init_and_add(&tunables->attr_set.kobj, &sugov_tunables_ktype,
  				   get_governor_parent_kobj(policy), "%s",
  				   schedutil_gov.name);
  	if (ret)
  		goto fail;
  
  out:
  	mutex_unlock(&global_tunables_lock);
  	return 0;
  
  fail:
  	policy->governor_data = NULL;
  	sugov_tunables_free(tunables);
  
  stop_kthread:
  	sugov_kthread_stop(sg_policy);
  
  free_sg_policy:
  	mutex_unlock(&global_tunables_lock);
  
  	sugov_policy_free(sg_policy);
  
  disable_fast_switch:
  	cpufreq_disable_fast_switch(policy);
  
  	pr_err("initialization failed (error %d)\n", ret);
  	return ret;
  }
  
  static void sugov_exit(struct cpufreq_policy *policy)
  {
  	struct sugov_policy *sg_policy = policy->governor_data;
  	struct sugov_tunables *tunables = sg_policy->tunables;
  	unsigned int count;
  
  	mutex_lock(&global_tunables_lock);
  
  	count = gov_attr_set_put(&tunables->attr_set, &sg_policy->tunables_hook);
  	policy->governor_data = NULL;
  	if (!count)
  		sugov_tunables_free(tunables);
  
  	mutex_unlock(&global_tunables_lock);
  
  	sugov_kthread_stop(sg_policy);
  	sugov_policy_free(sg_policy);
  	cpufreq_disable_fast_switch(policy);
  }
  
  static int sugov_start(struct cpufreq_policy *policy)
  {
  	struct sugov_policy *sg_policy = policy->governor_data;
  	unsigned int cpu;
  
  	sg_policy->freq_update_delay_ns = sg_policy->tunables->rate_limit_us * NSEC_PER_USEC;
  	sg_policy->last_freq_update_time = 0;
  	sg_policy->next_freq = UINT_MAX;
  	sg_policy->work_in_progress = false;
  	sg_policy->need_freq_update = false;
  	sg_policy->cached_raw_freq = 0;
  
  	for_each_cpu(cpu, policy->cpus) {
  		struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu);
  
  		sg_cpu->sg_policy = sg_policy;
  		if (policy_is_shared(policy)) {
  			sg_cpu->util = 0;
  			sg_cpu->max = 0;
  			sg_cpu->flags = SCHED_CPUFREQ_RT;
  			sg_cpu->last_update = 0;
  			sg_cpu->iowait_boost = 0;
  			sg_cpu->iowait_boost_max = policy->cpuinfo.max_freq;
  			cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util,
  						     sugov_update_shared);
  		} else {
  			cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util,
  						     sugov_update_single);
  		}
  	}
  	return 0;
  }
  
  static void sugov_stop(struct cpufreq_policy *policy)
  {
  	struct sugov_policy *sg_policy = policy->governor_data;
  	unsigned int cpu;
  
  	for_each_cpu(cpu, policy->cpus)
  		cpufreq_remove_update_util_hook(cpu);
  
  	synchronize_sched();
  
  	if (!policy->fast_switch_enabled) {
  		irq_work_sync(&sg_policy->irq_work);
  		kthread_cancel_work_sync(&sg_policy->work);
  	}
  }
  
  static void sugov_limits(struct cpufreq_policy *policy)
  {
  	struct sugov_policy *sg_policy = policy->governor_data;
  
  	if (!policy->fast_switch_enabled) {
  		mutex_lock(&sg_policy->work_lock);
  		cpufreq_policy_apply_limits(policy);
  		mutex_unlock(&sg_policy->work_lock);
  	}
  
  	sg_policy->need_freq_update = true;
  }
  
  static struct cpufreq_governor schedutil_gov = {
  	.name = "schedutil",
  	.owner = THIS_MODULE,
  	.init = sugov_init,
  	.exit = sugov_exit,
  	.start = sugov_start,
  	.stop = sugov_stop,
  	.limits = sugov_limits,
  };
  
  #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL
  struct cpufreq_governor *cpufreq_default_governor(void)
  {
  	return &schedutil_gov;
  }
  #endif
  
  static int __init sugov_register(void)
  {
  	return cpufreq_register_governor(&schedutil_gov);
  }
  fs_initcall(sugov_register);
  