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![Afzal Mohammed](/assets/img/avatar_default.png)
CPU frequency is guranteed to be changed on notifier callback with CPUFREQ_POSTCHANGE. Notifier callback with CPUFREQ_PRECHANGE does not gurantee a change in frequency; after it, if cpufreq driver is unable to change CPU to new frequency. This results in wrong information being fed to user (if setting CPU frequency fails) upon doing like, cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_setspeed Hence in userspace governer update cpu_cur_freq only if notifier has been called with POSTCHANGE. Signed-off-by: Afzal Mohammed <afzal@ti.com> Signed-off-by: Dave Jones <davej@redhat.com>
222 lines
5.9 KiB
C
222 lines
5.9 KiB
C
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/*
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* linux/drivers/cpufreq/cpufreq_userspace.c
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*
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* Copyright (C) 2001 Russell King
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* (C) 2002 - 2004 Dominik Brodowski <linux@brodo.de>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/smp.h>
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#include <linux/init.h>
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#include <linux/spinlock.h>
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#include <linux/interrupt.h>
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#include <linux/cpufreq.h>
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#include <linux/cpu.h>
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#include <linux/types.h>
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#include <linux/fs.h>
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#include <linux/sysfs.h>
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#include <linux/mutex.h>
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/**
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* A few values needed by the userspace governor
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*/
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static DEFINE_PER_CPU(unsigned int, cpu_max_freq);
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static DEFINE_PER_CPU(unsigned int, cpu_min_freq);
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static DEFINE_PER_CPU(unsigned int, cpu_cur_freq); /* current CPU freq */
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static DEFINE_PER_CPU(unsigned int, cpu_set_freq); /* CPU freq desired by
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userspace */
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static DEFINE_PER_CPU(unsigned int, cpu_is_managed);
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static DEFINE_MUTEX(userspace_mutex);
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static int cpus_using_userspace_governor;
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/* keep track of frequency transitions */
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static int
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userspace_cpufreq_notifier(struct notifier_block *nb, unsigned long val,
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void *data)
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{
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struct cpufreq_freqs *freq = data;
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if (!per_cpu(cpu_is_managed, freq->cpu))
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return 0;
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if (val == CPUFREQ_POSTCHANGE) {
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pr_debug("saving cpu_cur_freq of cpu %u to be %u kHz\n",
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freq->cpu, freq->new);
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per_cpu(cpu_cur_freq, freq->cpu) = freq->new;
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}
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return 0;
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}
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static struct notifier_block userspace_cpufreq_notifier_block = {
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.notifier_call = userspace_cpufreq_notifier
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};
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/**
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* cpufreq_set - set the CPU frequency
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* @policy: pointer to policy struct where freq is being set
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* @freq: target frequency in kHz
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*
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* Sets the CPU frequency to freq.
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*/
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static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
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{
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int ret = -EINVAL;
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pr_debug("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);
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mutex_lock(&userspace_mutex);
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if (!per_cpu(cpu_is_managed, policy->cpu))
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goto err;
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per_cpu(cpu_set_freq, policy->cpu) = freq;
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if (freq < per_cpu(cpu_min_freq, policy->cpu))
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freq = per_cpu(cpu_min_freq, policy->cpu);
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if (freq > per_cpu(cpu_max_freq, policy->cpu))
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freq = per_cpu(cpu_max_freq, policy->cpu);
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/*
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* We're safe from concurrent calls to ->target() here
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* as we hold the userspace_mutex lock. If we were calling
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* cpufreq_driver_target, a deadlock situation might occur:
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* A: cpufreq_set (lock userspace_mutex) ->
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* cpufreq_driver_target(lock policy->lock)
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* B: cpufreq_set_policy(lock policy->lock) ->
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* __cpufreq_governor ->
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* cpufreq_governor_userspace (lock userspace_mutex)
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*/
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ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
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err:
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mutex_unlock(&userspace_mutex);
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return ret;
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}
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static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
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{
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return sprintf(buf, "%u\n", per_cpu(cpu_cur_freq, policy->cpu));
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}
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static int cpufreq_governor_userspace(struct cpufreq_policy *policy,
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unsigned int event)
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{
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unsigned int cpu = policy->cpu;
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int rc = 0;
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switch (event) {
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case CPUFREQ_GOV_START:
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if (!cpu_online(cpu))
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return -EINVAL;
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BUG_ON(!policy->cur);
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mutex_lock(&userspace_mutex);
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if (cpus_using_userspace_governor == 0) {
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cpufreq_register_notifier(
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&userspace_cpufreq_notifier_block,
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CPUFREQ_TRANSITION_NOTIFIER);
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}
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cpus_using_userspace_governor++;
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per_cpu(cpu_is_managed, cpu) = 1;
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per_cpu(cpu_min_freq, cpu) = policy->min;
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per_cpu(cpu_max_freq, cpu) = policy->max;
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per_cpu(cpu_cur_freq, cpu) = policy->cur;
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per_cpu(cpu_set_freq, cpu) = policy->cur;
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pr_debug("managing cpu %u started "
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"(%u - %u kHz, currently %u kHz)\n",
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cpu,
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per_cpu(cpu_min_freq, cpu),
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per_cpu(cpu_max_freq, cpu),
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per_cpu(cpu_cur_freq, cpu));
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mutex_unlock(&userspace_mutex);
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break;
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case CPUFREQ_GOV_STOP:
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mutex_lock(&userspace_mutex);
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cpus_using_userspace_governor--;
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if (cpus_using_userspace_governor == 0) {
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cpufreq_unregister_notifier(
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&userspace_cpufreq_notifier_block,
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CPUFREQ_TRANSITION_NOTIFIER);
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}
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per_cpu(cpu_is_managed, cpu) = 0;
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per_cpu(cpu_min_freq, cpu) = 0;
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per_cpu(cpu_max_freq, cpu) = 0;
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per_cpu(cpu_set_freq, cpu) = 0;
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pr_debug("managing cpu %u stopped\n", cpu);
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mutex_unlock(&userspace_mutex);
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break;
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case CPUFREQ_GOV_LIMITS:
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mutex_lock(&userspace_mutex);
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pr_debug("limit event for cpu %u: %u - %u kHz, "
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"currently %u kHz, last set to %u kHz\n",
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cpu, policy->min, policy->max,
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per_cpu(cpu_cur_freq, cpu),
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per_cpu(cpu_set_freq, cpu));
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if (policy->max < per_cpu(cpu_set_freq, cpu)) {
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__cpufreq_driver_target(policy, policy->max,
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CPUFREQ_RELATION_H);
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} else if (policy->min > per_cpu(cpu_set_freq, cpu)) {
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__cpufreq_driver_target(policy, policy->min,
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CPUFREQ_RELATION_L);
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} else {
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__cpufreq_driver_target(policy,
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per_cpu(cpu_set_freq, cpu),
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CPUFREQ_RELATION_L);
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}
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per_cpu(cpu_min_freq, cpu) = policy->min;
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per_cpu(cpu_max_freq, cpu) = policy->max;
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per_cpu(cpu_cur_freq, cpu) = policy->cur;
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mutex_unlock(&userspace_mutex);
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break;
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}
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return rc;
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}
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#ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
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static
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#endif
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struct cpufreq_governor cpufreq_gov_userspace = {
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.name = "userspace",
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.governor = cpufreq_governor_userspace,
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.store_setspeed = cpufreq_set,
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.show_setspeed = show_speed,
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.owner = THIS_MODULE,
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};
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static int __init cpufreq_gov_userspace_init(void)
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{
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return cpufreq_register_governor(&cpufreq_gov_userspace);
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}
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static void __exit cpufreq_gov_userspace_exit(void)
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{
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cpufreq_unregister_governor(&cpufreq_gov_userspace);
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}
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MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>, "
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"Russell King <rmk@arm.linux.org.uk>");
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MODULE_DESCRIPTION("CPUfreq policy governor 'userspace'");
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MODULE_LICENSE("GPL");
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#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
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fs_initcall(cpufreq_gov_userspace_init);
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#else
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module_init(cpufreq_gov_userspace_init);
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#endif
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module_exit(cpufreq_gov_userspace_exit);
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