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Commit b8c80a0f authored by Quentin Perret's avatar Quentin Perret
Browse files

FROMLIST: PM / EM: Expose the Energy Model in sysfs 



Expose the Energy Model (read-only) of all performance domains in sysfs
for convenience. To do so, add a kobject to the CPU subsystem under the
umbrella of which a kobject for each performance domain is attached.

The resulting hierarchy is as follows for a platform with two
performance domains for example:

   /sys/devices/system/cpu/energy_model
   ├── pd0
   │   ├── cost
   │   ├── cpus
   │   ├── frequency
   │   └── power
   └── pd4
       ├── cost
       ├── cpus
       ├── frequency
       └── power

In this implementation, the kobject abstraction is only used as a
convenient way of exposing data to sysfs. However, it could also be
used in the future to allocate and release performance domains in a more
dynamic way using reference counting.

Change-Id: Ia98bcae21c3578e385be9c6b030c9adff8210909
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: default avatarQuentin Perret <quentin.perret@arm.com>
Message-Id: <20181016101513.26919-5-quentin.perret@arm.com>
Signed-off-by: default avatarQuentin Perret <quentin.perret@arm.com>
parent 9cbf2b68

include/linux/energy_model.h

+2 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ struct em_cap_state { 
 * em_perf_domain - Performance domain

 * @table:		List of capacity states, in ascending order

 * @nr_cap_states:	Number of capacity states

 * @kobj:		Kobject used to expose the domain in sysfs

 * @cpus:		Cpumask covering the CPUs of the domain

 *

 * A "performance domain" represents a group of CPUs whose performance is
@@ -37,6 +38,7 @@ struct em_cap_state { 
struct em_perf_domain {

	struct em_cap_state *table;

	int nr_cap_states;

	struct kobject kobj;

	unsigned long cpus[0];

};

kernel/power/energy_model.c

+90 −0
Original line number Diff line number Diff line
@@ -23,6 +23,82 @@ static DEFINE_PER_CPU(struct em_perf_domain *, em_data); 
 */

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)

{
@@ -102,6 +178,11 @@ static struct em_perf_domain *em_create_pd(cpumask_t *span, int nr_states, 
	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:
@@ -155,6 +236,15 @@ int em_register_perf_domain(cpumask_t *span, unsigned int nr_states, 
	 */

	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))) {