linux/drivers/base/arch_topology.c

/*
 * Arch specific cpu topology information
 *
 * Copyright (C) 2016, ARM Ltd.
 * Written by: Juri Lelli, ARM Ltd.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Released under the GPLv2 only.
 * SPDX-License-Identifier: GPL-2.0
 */

#include <linux/acpi.h>
#include <linux/arch_topology.h>
#include <linux/cpu.h>
#include <linux/cpufreq.h>
#include <linux/device.h>
#include <linux/of.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/sched/topology.h>

static DEFINE_MUTEX(cpu_scale_mutex);
static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;

unsigned long topology_get_cpu_scale(struct sched_domain *sd, int cpu)
{
	return per_cpu(cpu_scale, cpu);
}

void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity)
{
	per_cpu(cpu_scale, cpu) = capacity;
}

static ssize_t cpu_capacity_show(struct device *dev,
				 struct device_attribute *attr,
				 char *buf)
{
	struct cpu *cpu = container_of(dev, struct cpu, dev);

	return sprintf(buf, "%lu\n", topology_get_cpu_scale(NULL, cpu->dev.id));
}

static ssize_t cpu_capacity_store(struct device *dev,
				  struct device_attribute *attr,
				  const char *buf,
				  size_t count)
{
	struct cpu *cpu = container_of(dev, struct cpu, dev);
	int this_cpu = cpu->dev.id;
	int i;
	unsigned long new_capacity;
	ssize_t ret;

	if (!count)
		return 0;

	ret = kstrtoul(buf, 0, &new_capacity);
	if (ret)
		return ret;
	if (new_capacity > SCHED_CAPACITY_SCALE)
		return -EINVAL;

	mutex_lock(&cpu_scale_mutex);
	for_each_cpu(i, &cpu_topology[this_cpu].core_sibling)
		topology_set_cpu_scale(i, new_capacity);
	mutex_unlock(&cpu_scale_mutex);

	return count;
}

static DEVICE_ATTR_RW(cpu_capacity);

static int register_cpu_capacity_sysctl(void)
{
	int i;
	struct device *cpu;

	for_each_possible_cpu(i) {
		cpu = get_cpu_device(i);
		if (!cpu) {
			pr_err("%s: too early to get CPU%d device!\n",
			       __func__, i);
			continue;
		}
		device_create_file(cpu, &dev_attr_cpu_capacity);
	}

	return 0;
}
subsys_initcall(register_cpu_capacity_sysctl);

static u32 capacity_scale;
static u32 *raw_capacity;
static bool cap_parsing_failed;

void topology_normalize_cpu_scale(void)
{
	u64 capacity;
	int cpu;

	if (!raw_capacity || cap_parsing_failed)
		return;

	pr_debug("cpu_capacity: capacity_scale=%u\n", capacity_scale);
	mutex_lock(&cpu_scale_mutex);
	for_each_possible_cpu(cpu) {
		pr_debug("cpu_capacity: cpu=%d raw_capacity=%u\n",
			 cpu, raw_capacity[cpu]);
		capacity = (raw_capacity[cpu] << SCHED_CAPACITY_SHIFT)
			/ capacity_scale;
		topology_set_cpu_scale(cpu, capacity);
		pr_debug("cpu_capacity: CPU%d cpu_capacity=%lu\n",
			cpu, topology_get_cpu_scale(NULL, cpu));
	}
	mutex_unlock(&cpu_scale_mutex);
}

int __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
{
	int ret = 1;
	u32 cpu_capacity;

	if (cap_parsing_failed)
		return !ret;

	ret = of_property_read_u32(cpu_node, "capacity-dmips-mhz",
				   &cpu_capacity);
	if (!ret) {
		if (!raw_capacity) {
			raw_capacity = kcalloc(num_possible_cpus(),
					       sizeof(*raw_capacity),
					       GFP_KERNEL);
			if (!raw_capacity) {
				pr_err("cpu_capacity: failed to allocate memory for raw capacities\n");
				cap_parsing_failed = true;
				return 0;
			}
		}
		capacity_scale = max(cpu_capacity, capacity_scale);
		raw_capacity[cpu] = cpu_capacity;
		pr_debug("cpu_capacity: %s cpu_capacity=%u (raw)\n",
			cpu_node->full_name, raw_capacity[cpu]);
	} else {
		if (raw_capacity) {
			pr_err("cpu_capacity: missing %s raw capacity\n",
				cpu_node->full_name);
			pr_err("cpu_capacity: partial information: fallback to 1024 for all CPUs\n");
		}
		cap_parsing_failed = true;
		kfree(raw_capacity);
	}

	return !ret;
}

#ifdef CONFIG_CPU_FREQ
static cpumask_var_t cpus_to_visit;
static bool cap_parsing_done;
static void parsing_done_workfn(struct work_struct *work);
static DECLARE_WORK(parsing_done_work, parsing_done_workfn);

static int
init_cpu_capacity_callback(struct notifier_block *nb,
			   unsigned long val,
			   void *data)
{
	struct cpufreq_policy *policy = data;
	int cpu;

	if (cap_parsing_failed || cap_parsing_done)
		return 0;

	switch (val) {
	case CPUFREQ_NOTIFY:
		pr_debug("cpu_capacity: init cpu capacity for CPUs [%*pbl] (to_visit=%*pbl)\n",
				cpumask_pr_args(policy->related_cpus),
				cpumask_pr_args(cpus_to_visit));
		cpumask_andnot(cpus_to_visit, cpus_to_visit,
			       policy->related_cpus);
		for_each_cpu(cpu, policy->related_cpus) {
			raw_capacity[cpu] = topology_get_cpu_scale(NULL, cpu) *
					    policy->cpuinfo.max_freq / 1000UL;
			capacity_scale = max(raw_capacity[cpu], capacity_scale);
		}
		if (cpumask_empty(cpus_to_visit)) {
			topology_normalize_cpu_scale();
			kfree(raw_capacity);
			pr_debug("cpu_capacity: parsing done\n");
			cap_parsing_done = true;
			schedule_work(&parsing_done_work);
		}
	}
	return 0;
}

static struct notifier_block init_cpu_capacity_notifier = {
	.notifier_call = init_cpu_capacity_callback,
};

static int __init register_cpufreq_notifier(void)
{
	/*
	 * on ACPI-based systems we need to use the default cpu capacity
	 * until we have the necessary code to parse the cpu capacity, so
	 * skip registering cpufreq notifier.
	 */
	if (!acpi_disabled || !raw_capacity)
		return -EINVAL;

	if (!alloc_cpumask_var(&cpus_to_visit, GFP_KERNEL)) {
		pr_err("cpu_capacity: failed to allocate memory for cpus_to_visit\n");
		return -ENOMEM;
	}

	cpumask_copy(cpus_to_visit, cpu_possible_mask);

	return cpufreq_register_notifier(&init_cpu_capacity_notifier,
					 CPUFREQ_POLICY_NOTIFIER);
}
core_initcall(register_cpufreq_notifier);

static void parsing_done_workfn(struct work_struct *work)
{
	cpufreq_unregister_notifier(&init_cpu_capacity_notifier,
					 CPUFREQ_POLICY_NOTIFIER);
}

#else
static int __init free_raw_capacity(void)
{
	kfree(raw_capacity);

	return 0;
}
core_initcall(free_raw_capacity);
#endif