kernel/power/energy_model.c - kernel/common.git - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Energy Model of CPUs
  *
  * Copyright (c) 2018, Arm ltd.
  * Written by: Quentin Perret, Arm ltd.
  */

 #define pr_fmt(fmt) "energy_model: " fmt

 #include <linux/cpu.h>
 #include <linux/cpumask.h>
 #include <linux/energy_model.h>
 #include <linux/sched/topology.h>
 #include <linux/slab.h>

 /* Mapping of each CPU to the performance domain to which it belongs. */
 static DEFINE_PER_CPU(struct em_perf_domain *, em_data);

 /*
  * Mutex serializing the registrations of performance domains and letting
  * callbacks defined by drivers sleep.
  */
 static DEFINE_MUTEX(em_pd_mutex);

 static struct kobject *em_kobject;

 /* Getters for the attributes of em_perf_domain objects */
 struct em_pd_attr {
 	struct attribute attr;
 	ssize_t (*show)(struct em_perf_domain *pd, char *buf);
 	ssize_t (*store)(struct em_perf_domain *pd, const char *buf, size_t s);
 };

 #define EM_ATTR_LEN 13
 #define show_table_attr(_attr) \
 static ssize_t show_##_attr(struct em_perf_domain *pd, char *buf) \
 { \
 	ssize_t cnt = 0; \
 	int i; \
 	for (i = 0; i < pd->nr_cap_states; i++) { \
 		if (cnt >= (ssize_t) (PAGE_SIZE / sizeof(char) \
 				      - (EM_ATTR_LEN + 2))) \
 			goto out; \
 		cnt += scnprintf(&buf[cnt], EM_ATTR_LEN + 1, "%lu ", \
 				 pd->table[i]._attr); \
 	} \
 out: \
 	cnt += sprintf(&buf[cnt], "\n"); \
 	return cnt; \
 }

 show_table_attr(power);
 show_table_attr(frequency);
 show_table_attr(cost);

 static ssize_t show_cpus(struct em_perf_domain *pd, char *buf)
 {
 	return sprintf(buf, "%*pbl\n", cpumask_pr_args(to_cpumask(pd->cpus)));
 }

 #define pd_attr(_name) em_pd_##_name##_attr
 #define define_pd_attr(_name) static struct em_pd_attr pd_attr(_name) = \
 		__ATTR(_name, 0444, show_##_name, NULL)

 define_pd_attr(power);
 define_pd_attr(frequency);
 define_pd_attr(cost);
 define_pd_attr(cpus);

 static struct attribute *em_pd_default_attrs[] = {
 	&pd_attr(power).attr,
 	&pd_attr(frequency).attr,
 	&pd_attr(cost).attr,
 	&pd_attr(cpus).attr,
 	NULL
 };

 #define to_pd(k) container_of(k, struct em_perf_domain, kobj)
 #define to_pd_attr(a) container_of(a, struct em_pd_attr, attr)

 static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf)
 {
 	struct em_perf_domain *pd = to_pd(kobj);
 	struct em_pd_attr *pd_attr = to_pd_attr(attr);
 	ssize_t ret;

 	ret = pd_attr->show(pd, buf);

 	return ret;
 }

 static const struct sysfs_ops em_pd_sysfs_ops = {
 	.show	= show,
 };

 static struct kobj_type ktype_em_pd = {
 	.sysfs_ops	= &em_pd_sysfs_ops,
 	.default_attrs	= em_pd_default_attrs,
 };

 static struct em_perf_domain *em_create_pd(cpumask_t *span, int nr_states,
 						struct em_data_callback *cb)
 {
 	unsigned long opp_eff, prev_opp_eff = ULONG_MAX;
 	unsigned long power, freq, prev_freq = 0;
 	int i, ret, cpu = cpumask_first(span);
 	struct em_cap_state *table;
 	struct em_perf_domain *pd;
 	u64 fmax;

 	if (!cb->active_power)
 		return NULL;

 	pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
 	if (!pd)
 		return NULL;

 	table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL);
 	if (!table)
 		goto free_pd;

 	/* Build the list of capacity states for this performance domain */
 	for (i = 0, freq = 0; i < nr_states; i++, freq++) {
 		/*
 		 * active_power() is a driver callback which ceils 'freq' to
 		 * lowest capacity state of 'cpu' above 'freq' and updates
 		 * 'power' and 'freq' accordingly.
 		 */
 		ret = cb->active_power(&power, &freq, cpu);
 		if (ret) {
 			pr_err("pd%d: invalid cap. state: %d\n", cpu, ret);
 			goto free_cs_table;
 		}

 		/*
 		 * We expect the driver callback to increase the frequency for
 		 * higher capacity states.
 		 */
 		if (freq <= prev_freq) {
 			pr_err("pd%d: non-increasing freq: %lu\n", cpu, freq);
 			goto free_cs_table;
 		}

 		/*
 		 * The power returned by active_state() is expected to be
 		 * positive, in milli-watts and to fit into 16 bits.
 		 */
 		if (!power || power > EM_CPU_MAX_POWER) {
 			pr_err("pd%d: invalid power: %lu\n", cpu, power);
 			goto free_cs_table;
 		}

 		table[i].power = power;
 		table[i].frequency = prev_freq = freq;

 		/*
 		 * The hertz/watts efficiency ratio should decrease as the
 		 * frequency grows on sane platforms. But this isn't always
 		 * true in practice so warn the user if a higher OPP is more
 		 * power efficient than a lower one.
 		 */
 		opp_eff = freq / power;
 		if (opp_eff >= prev_opp_eff)
 			pr_warn("pd%d: hertz/watts ratio non-monotonically decreasing: em_cap_state %d >= em_cap_state%d\n",
 					cpu, i, i - 1);
 		prev_opp_eff = opp_eff;
 	}

 	/* Compute the cost of each capacity_state. */
 	fmax = (u64) table[nr_states - 1].frequency;
 	for (i = 0; i < nr_states; i++) {
 		table[i].cost = div64_u64(fmax * table[i].power,
 					  table[i].frequency);
 	}

 	pd->table = table;
 	pd->nr_cap_states = nr_states;
 	cpumask_copy(to_cpumask(pd->cpus), span);

 	ret = kobject_init_and_add(&pd->kobj, &ktype_em_pd, em_kobject,
 				   "pd%u", cpu);
 	if (ret)
 		pr_err("pd%d: failed kobject_init_and_add(): %d\n", cpu, ret);

 	return pd;

 free_cs_table:
 	kfree(table);
 free_pd:
 	kfree(pd);

 	return NULL;
 }

 /**
  * em_cpu_get() - Return the performance domain for a CPU
  * @cpu : CPU to find the performance domain for
  *
  * Return: the performance domain to which 'cpu' belongs, or NULL if it doesn't
  * exist.
  */
 struct em_perf_domain *em_cpu_get(int cpu)
 {
 	return READ_ONCE(per_cpu(em_data, cpu));
 }
 EXPORT_SYMBOL_GPL(em_cpu_get);

 /**
  * em_register_perf_domain() - Register the Energy Model of a performance domain
  * @span	: Mask of CPUs in the performance domain
  * @nr_states	: Number of capacity states to register
  * @cb		: Callback functions providing the data of the Energy Model
  *
  * Create Energy Model tables for a performance domain using the callbacks
  * defined in cb.
  *
  * If multiple clients register the same performance domain, all but the first
  * registration will be ignored.
  *
  * Return 0 on success
  */
 int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
 						struct em_data_callback *cb)
 {
 	unsigned long cap, prev_cap = 0;
 	struct em_perf_domain *pd;
 	int cpu, ret = 0;

 	if (!span || !nr_states || !cb)
 		return -EINVAL;

 	/*
 	 * Use a mutex to serialize the registration of performance domains and
 	 * let the driver-defined callback functions sleep.
 	 */
 	mutex_lock(&em_pd_mutex);

 	if (!em_kobject) {
 		em_kobject = kobject_create_and_add("energy_model",
 						&cpu_subsys.dev_root->kobj);
 		if (!em_kobject) {
 			ret = -ENODEV;
 			goto unlock;
 		}
 	}

 	for_each_cpu(cpu, span) {
 		/* Make sure we don't register again an existing domain. */
 		if (READ_ONCE(per_cpu(em_data, cpu))) {
 			ret = -EEXIST;
 			goto unlock;
 		}

 		/*
 		 * All CPUs of a domain must have the same micro-architecture
 		 * since they all share the same table.
 		 */
 		cap = arch_scale_cpu_capacity(NULL, cpu);
 		if (prev_cap && prev_cap != cap) {
 			pr_err("CPUs of %*pbl must have the same capacity\n",
 							cpumask_pr_args(span));
 			ret = -EINVAL;
 			goto unlock;
 		}
 		prev_cap = cap;
 	}

 	/* Create the performance domain and add it to the Energy Model. */
 	pd = em_create_pd(span, nr_states, cb);
 	if (!pd) {
 		ret = -EINVAL;
 		goto unlock;
 	}

 	for_each_cpu(cpu, span) {
 		/*
 		 * The per-cpu array can be read concurrently from em_cpu_get().
 		 * The barrier enforces the ordering needed to make sure readers
 		 * can only access well formed em_perf_domain structs.
 		 */
 		smp_store_release(per_cpu_ptr(&em_data, cpu), pd);
 	}

 	pr_debug("Created perf domain %*pbl\n", cpumask_pr_args(span));
 unlock:
 	mutex_unlock(&em_pd_mutex);

 	return ret;
 }
 EXPORT_SYMBOL_GPL(em_register_perf_domain);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Energy Model of CPUs
	*
	* Copyright (c) 2018, Arm ltd.
	* Written by: Quentin Perret, Arm ltd.
	*/

	#define pr_fmt(fmt) "energy_model: " fmt

	#include <linux/cpu.h>
	#include <linux/cpumask.h>
	#include <linux/energy_model.h>
	#include <linux/sched/topology.h>
	#include <linux/slab.h>

	/* Mapping of each CPU to the performance domain to which it belongs. */
	static DEFINE_PER_CPU(struct em_perf_domain *, em_data);

	/*
	* Mutex serializing the registrations of performance domains and letting
	* callbacks defined by drivers sleep.
	*/
	static DEFINE_MUTEX(em_pd_mutex);

	static struct kobject *em_kobject;

	/* Getters for the attributes of em_perf_domain objects */
	struct em_pd_attr {
	struct attribute attr;
	ssize_t (show)(struct em_perf_domain pd, char *buf);
	ssize_t (store)(struct em_perf_domain pd, const char *buf, size_t s);
	};

	#define EM_ATTR_LEN 13
	#define show_table_attr(_attr) \
	static ssize_t show_##_attr(struct em_perf_domain pd, char buf) \
	{ \
	ssize_t cnt = 0; \
	int i; \
	for (i = 0; i < pd->nr_cap_states; i++) { \
	if (cnt >= (ssize_t) (PAGE_SIZE / sizeof(char) \
	- (EM_ATTR_LEN + 2))) \
	goto out; \
	cnt += scnprintf(&buf[cnt], EM_ATTR_LEN + 1, "%lu ", \
	pd->table[i]._attr); \
	} \
	out: \
	cnt += sprintf(&buf[cnt], "\n"); \
	return cnt; \
	}

	show_table_attr(power);
	show_table_attr(frequency);
	show_table_attr(cost);

	static ssize_t show_cpus(struct em_perf_domain pd, char buf)
	{
	return sprintf(buf, "%*pbl\n", cpumask_pr_args(to_cpumask(pd->cpus)));
	}

	#define pd_attr(_name) em_pd_##_name##_attr
	#define define_pd_attr(_name) static struct em_pd_attr pd_attr(_name) = \
	__ATTR(_name, 0444, show_##_name, NULL)

	define_pd_attr(power);
	define_pd_attr(frequency);
	define_pd_attr(cost);
	define_pd_attr(cpus);

	static struct attribute *em_pd_default_attrs[] = {
	&pd_attr(power).attr,
	&pd_attr(frequency).attr,
	&pd_attr(cost).attr,
	&pd_attr(cpus).attr,
	NULL
	};

	#define to_pd(k) container_of(k, struct em_perf_domain, kobj)
	#define to_pd_attr(a) container_of(a, struct em_pd_attr, attr)

	static ssize_t show(struct kobject kobj, struct attribute attr, char *buf)
	{
	struct em_perf_domain *pd = to_pd(kobj);
	struct em_pd_attr *pd_attr = to_pd_attr(attr);
	ssize_t ret;

	ret = pd_attr->show(pd, buf);

	return ret;
	}

	static const struct sysfs_ops em_pd_sysfs_ops = {
	.show = show,
	};

	static struct kobj_type ktype_em_pd = {
	.sysfs_ops = &em_pd_sysfs_ops,
	.default_attrs = em_pd_default_attrs,
	};

	static struct em_perf_domain em_create_pd(cpumask_t span, int nr_states,
	struct em_data_callback *cb)
	{
	unsigned long opp_eff, prev_opp_eff = ULONG_MAX;
	unsigned long power, freq, prev_freq = 0;
	int i, ret, cpu = cpumask_first(span);
	struct em_cap_state *table;
	struct em_perf_domain *pd;
	u64 fmax;

	if (!cb->active_power)
	return NULL;

	pd = kzalloc(sizeof(*pd) + cpumask_size(), GFP_KERNEL);
	if (!pd)
	return NULL;

	table = kcalloc(nr_states, sizeof(*table), GFP_KERNEL);
	if (!table)
	goto free_pd;

	/* Build the list of capacity states for this performance domain */
	for (i = 0, freq = 0; i < nr_states; i++, freq++) {
	/*
	* active_power() is a driver callback which ceils 'freq' to
	* lowest capacity state of 'cpu' above 'freq' and updates
	* 'power' and 'freq' accordingly.
	*/
	ret = cb->active_power(&power, &freq, cpu);
	if (ret) {
	pr_err("pd%d: invalid cap. state: %d\n", cpu, ret);
	goto free_cs_table;
	}

	/*
	* We expect the driver callback to increase the frequency for
	* higher capacity states.
	*/
	if (freq <= prev_freq) {
	pr_err("pd%d: non-increasing freq: %lu\n", cpu, freq);
	goto free_cs_table;
	}

	/*
	* The power returned by active_state() is expected to be
	* positive, in milli-watts and to fit into 16 bits.
	*/
	if (!power \|\| power > EM_CPU_MAX_POWER) {
	pr_err("pd%d: invalid power: %lu\n", cpu, power);
	goto free_cs_table;
	}

	table[i].power = power;
	table[i].frequency = prev_freq = freq;

	/*
	* The hertz/watts efficiency ratio should decrease as the
	* frequency grows on sane platforms. But this isn't always
	* true in practice so warn the user if a higher OPP is more
	* power efficient than a lower one.
	*/
	opp_eff = freq / power;
	if (opp_eff >= prev_opp_eff)
	pr_warn("pd%d: hertz/watts ratio non-monotonically decreasing: em_cap_state %d >= em_cap_state%d\n",
	cpu, i, i - 1);
	prev_opp_eff = opp_eff;
	}

	/* Compute the cost of each capacity_state. */
	fmax = (u64) table[nr_states - 1].frequency;
	for (i = 0; i < nr_states; i++) {
	table[i].cost = div64_u64(fmax * table[i].power,
	table[i].frequency);
	}

	pd->table = table;
	pd->nr_cap_states = nr_states;
	cpumask_copy(to_cpumask(pd->cpus), span);

	ret = kobject_init_and_add(&pd->kobj, &ktype_em_pd, em_kobject,
	"pd%u", cpu);
	if (ret)
	pr_err("pd%d: failed kobject_init_and_add(): %d\n", cpu, ret);

	return pd;

	free_cs_table:
	kfree(table);
	free_pd:
	kfree(pd);

	return NULL;
	}

	/**
	* em_cpu_get() - Return the performance domain for a CPU
	* @cpu : CPU to find the performance domain for
	*
	* Return: the performance domain to which 'cpu' belongs, or NULL if it doesn't
	* exist.
	*/
	struct em_perf_domain *em_cpu_get(int cpu)
	{
	return READ_ONCE(per_cpu(em_data, cpu));
	}
	EXPORT_SYMBOL_GPL(em_cpu_get);

	/**
	* em_register_perf_domain() - Register the Energy Model of a performance domain
	* @span : Mask of CPUs in the performance domain
	* @nr_states : Number of capacity states to register
	* @cb : Callback functions providing the data of the Energy Model
	*
	* Create Energy Model tables for a performance domain using the callbacks
	* defined in cb.
	*
	* If multiple clients register the same performance domain, all but the first
	* registration will be ignored.
	*
	* Return 0 on success
	*/
	int em_register_perf_domain(cpumask_t *span, unsigned int nr_states,
	struct em_data_callback *cb)
	{
	unsigned long cap, prev_cap = 0;
	struct em_perf_domain *pd;
	int cpu, ret = 0;

	if (!span \|\| !nr_states \|\| !cb)
	return -EINVAL;

	/*
	* Use a mutex to serialize the registration of performance domains and
	* let the driver-defined callback functions sleep.
	*/
	mutex_lock(&em_pd_mutex);

	if (!em_kobject) {
	em_kobject = kobject_create_and_add("energy_model",
	&cpu_subsys.dev_root->kobj);
	if (!em_kobject) {
	ret = -ENODEV;
	goto unlock;
	}
	}

	for_each_cpu(cpu, span) {
	/* Make sure we don't register again an existing domain. */
	if (READ_ONCE(per_cpu(em_data, cpu))) {
	ret = -EEXIST;
	goto unlock;
	}

	/*
	* All CPUs of a domain must have the same micro-architecture
	* since they all share the same table.
	*/
	cap = arch_scale_cpu_capacity(NULL, cpu);
	if (prev_cap && prev_cap != cap) {
	pr_err("CPUs of %*pbl must have the same capacity\n",
	cpumask_pr_args(span));
	ret = -EINVAL;
	goto unlock;
	}
	prev_cap = cap;
	}

	/* Create the performance domain and add it to the Energy Model. */
	pd = em_create_pd(span, nr_states, cb);
	if (!pd) {
	ret = -EINVAL;
	goto unlock;
	}

	for_each_cpu(cpu, span) {
	/*
	* The per-cpu array can be read concurrently from em_cpu_get().
	* The barrier enforces the ordering needed to make sure readers
	* can only access well formed em_perf_domain structs.
	*/
	smp_store_release(per_cpu_ptr(&em_data, cpu), pd);
	}

	pr_debug("Created perf domain %*pbl\n", cpumask_pr_args(span));
	unlock:
	mutex_unlock(&em_pd_mutex);

	return ret;
	}
	EXPORT_SYMBOL_GPL(em_register_perf_domain);