// SPDX-License-Identifier: GPL-2.0-only

/*
 *  linux/drivers/cpufreq/cpufreq_userspace.c
 *
 *  Copyright (C)  2001 Russell King
 *            (C)  2002 - 2004 Dominik Brodowski <linux@brodo.de>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/cpufreq.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>

struct userspace_policy {
        unsigned int is_managed;
        unsigned int setspeed;
        struct mutex mutex;
};

/**
 * cpufreq_set - set the CPU frequency
 * @policy: pointer to policy struct where freq is being set
 * @freq: target frequency in kHz
 *
 * Sets the CPU frequency to freq.
 */
static int cpufreq_set(struct cpufreq_policy *policy, unsigned int freq)
{
        int ret = -EINVAL;
        struct userspace_policy *userspace = policy->governor_data;

        pr_debug("cpufreq_set for cpu %u, freq %u kHz\n", policy->cpu, freq);

        mutex_lock(&userspace->mutex);
        if (!userspace->is_managed)
                goto err;

        userspace->setspeed = freq;

        ret = __cpufreq_driver_target(policy, freq, CPUFREQ_RELATION_L);
 err:
        mutex_unlock(&userspace->mutex);
        return ret;
}

static ssize_t show_speed(struct cpufreq_policy *policy, char *buf)
{
        struct userspace_policy *userspace = policy->governor_data;

        return sprintf(buf, "%u\n", userspace->setspeed);
}

static int cpufreq_userspace_policy_init(struct cpufreq_policy *policy)
{
        struct userspace_policy *userspace;

        userspace = kzalloc_obj(*userspace);
        if (!userspace)
                return -ENOMEM;

        mutex_init(&userspace->mutex);

        policy->governor_data = userspace;
        return 0;
}

/*
 * Any routine that writes to the policy struct will hold the "rwsem" of
 * policy struct that means it is free to free "governor_data" here.
 */
static void cpufreq_userspace_policy_exit(struct cpufreq_policy *policy)
{
        kfree(policy->governor_data);
        policy->governor_data = NULL;
}

static int cpufreq_userspace_policy_start(struct cpufreq_policy *policy)
{
        struct userspace_policy *userspace = policy->governor_data;

        BUG_ON(!policy->cur);
        pr_debug("started managing cpu %u\n", policy->cpu);

        mutex_lock(&userspace->mutex);
        userspace->is_managed = 1;
        userspace->setspeed = policy->cur;
        mutex_unlock(&userspace->mutex);
        return 0;
}

static void cpufreq_userspace_policy_stop(struct cpufreq_policy *policy)
{
        struct userspace_policy *userspace = policy->governor_data;

        pr_debug("managing cpu %u stopped\n", policy->cpu);

        mutex_lock(&userspace->mutex);
        userspace->is_managed = 0;
        userspace->setspeed = 0;
        mutex_unlock(&userspace->mutex);
}

static void cpufreq_userspace_policy_limits(struct cpufreq_policy *policy)
{
        struct userspace_policy *userspace = policy->governor_data;

        mutex_lock(&userspace->mutex);

        pr_debug("limit event for cpu %u: %u - %u kHz, currently %u kHz, last set to %u kHz\n",
                 policy->cpu, policy->min, policy->max, policy->cur, userspace->setspeed);

        if (policy->max < userspace->setspeed)
                __cpufreq_driver_target(policy, policy->max,
                                        CPUFREQ_RELATION_H);
        else if (policy->min > userspace->setspeed)
                __cpufreq_driver_target(policy, policy->min,
                                        CPUFREQ_RELATION_L);
        else
                __cpufreq_driver_target(policy, userspace->setspeed,
                                        CPUFREQ_RELATION_L);

        mutex_unlock(&userspace->mutex);
}

static struct cpufreq_governor cpufreq_gov_userspace = {
        .name           = "userspace",
        .init           = cpufreq_userspace_policy_init,
        .exit           = cpufreq_userspace_policy_exit,
        .start          = cpufreq_userspace_policy_start,
        .stop           = cpufreq_userspace_policy_stop,
        .limits         = cpufreq_userspace_policy_limits,
        .store_setspeed = cpufreq_set,
        .show_setspeed  = show_speed,
        .owner          = THIS_MODULE,
        .flags          = CPUFREQ_GOV_STRICT_TARGET,
};

MODULE_AUTHOR("Dominik Brodowski <linux@brodo.de>, "
                "Russell King <rmk@arm.linux.org.uk>");
MODULE_DESCRIPTION("CPUfreq policy governor 'userspace'");
MODULE_LICENSE("GPL");

#ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE
struct cpufreq_governor *cpufreq_default_governor(void)
{
        return &cpufreq_gov_userspace;
}
#endif

cpufreq_governor_init(cpufreq_gov_userspace);
cpufreq_governor_exit(cpufreq_gov_userspace);