/*
 * processor_thermal.c - Passive cooling submodule of the ACPI processor driver
 *
 *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
 *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
 *  Copyright (C) 2004       Dominik Brodowski <linux@brodo.de>
 *  Copyright (C) 2004  Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
 *                      - Added processor hotplug support
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or (at
 *  your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  General Public License for more details.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/cpufreq.h>
#include <linux/acpi.h>
#include <acpi/processor.h>
#include <linux/uaccess.h>

#define PREFIX "ACPI: "

#define ACPI_PROCESSOR_CLASS            "processor"
#define _COMPONENT              ACPI_PROCESSOR_COMPONENT
ACPI_MODULE_NAME("processor_thermal");

#ifdef CONFIG_CPU_FREQ

/* If a passive cooling situation is detected, primarily CPUfreq is used, as it
 * offers (in most cases) voltage scaling in addition to frequency scaling, and
 * thus a cubic (instead of linear) reduction of energy. Also, we allow for
 * _any_ cpufreq driver and not only the acpi-cpufreq driver.
 */

#define CPUFREQ_THERMAL_MIN_STEP 0
#define CPUFREQ_THERMAL_MAX_STEP 3

static DEFINE_PER_CPU(unsigned int, cpufreq_thermal_reduction_pctg);
static unsigned int acpi_thermal_cpufreq_is_init = 0;

#define reduction_pctg(cpu) \
        per_cpu(cpufreq_thermal_reduction_pctg, phys_package_first_cpu(cpu))

/*
 * Emulate "per package data" using per cpu data (which should really be
 * provided elsewhere)
 *
 * Note we can lose a CPU on cpu hotunplug, in this case we forget the state
 * temporarily. Fortunately that's not a big issue here (I hope)
 */
static int phys_package_first_cpu(int cpu)
{
        int i;
        int id = topology_physical_package_id(cpu);

        for_each_online_cpu(i)
                if (topology_physical_package_id(i) == id)
                        return i;
        return 0;
}

static int cpu_has_cpufreq(unsigned int cpu)
{
        struct cpufreq_policy policy;
        if (!acpi_thermal_cpufreq_is_init || cpufreq_get_policy(&policy, cpu))
                return 0;
        return 1;
}

static int acpi_thermal_cpufreq_notifier(struct notifier_block *nb,
                                         unsigned long event, void *data)
{
        struct cpufreq_policy *policy = data;
        unsigned long max_freq = 0;

        if (event != CPUFREQ_ADJUST)
                goto out;

        max_freq = (
            policy->cpuinfo.max_freq *
            (100 - reduction_pctg(policy->cpu) * 20)
        ) / 100;

        cpufreq_verify_within_limits(policy, 0, max_freq);

      out:
        return 0;
}

static struct notifier_block acpi_thermal_cpufreq_notifier_block = {
        .notifier_call = acpi_thermal_cpufreq_notifier,
};

static int cpufreq_get_max_state(unsigned int cpu)
{
        if (!cpu_has_cpufreq(cpu))
                return 0;

        return CPUFREQ_THERMAL_MAX_STEP;
}

static int cpufreq_get_cur_state(unsigned int cpu)
{
        if (!cpu_has_cpufreq(cpu))
                return 0;

        return reduction_pctg(cpu);
}

static int cpufreq_set_cur_state(unsigned int cpu, int state)
{
        int i;

        if (!cpu_has_cpufreq(cpu))
                return 0;

        reduction_pctg(cpu) = state;

        /*
         * Update all the CPUs in the same package because they all
         * contribute to the temperature and often share the same
         * frequency.
         */
        for_each_online_cpu(i) {
                if (topology_physical_package_id(i) ==
                    topology_physical_package_id(cpu))
                        cpufreq_update_policy(i);
        }
        return 0;
}

void acpi_thermal_cpufreq_init(void)
{
        int i;

        i = cpufreq_register_notifier(&acpi_thermal_cpufreq_notifier_block,
                                      CPUFREQ_POLICY_NOTIFIER);
        if (!i)
                acpi_thermal_cpufreq_is_init = 1;
}

void acpi_thermal_cpufreq_exit(void)
{
        if (acpi_thermal_cpufreq_is_init)
                cpufreq_unregister_notifier
                    (&acpi_thermal_cpufreq_notifier_block,
                     CPUFREQ_POLICY_NOTIFIER);

        acpi_thermal_cpufreq_is_init = 0;
}

#else                           /* ! CONFIG_CPU_FREQ */
static int cpufreq_get_max_state(unsigned int cpu)
{
        return 0;
}

static int cpufreq_get_cur_state(unsigned int cpu)
{
        return 0;
}

static int cpufreq_set_cur_state(unsigned int cpu, int state)
{
        return 0;
}

#endif

/* thermal cooling device callbacks */
static int acpi_processor_max_state(struct acpi_processor *pr)
{
        int max_state = 0;

        /*
         * There exists four states according to
         * cpufreq_thermal_reduction_pctg. 0, 1, 2, 3
         */
        max_state += cpufreq_get_max_state(pr->id);
        if (pr->flags.throttling)
                max_state += (pr->throttling.state_count -1);

        return max_state;
}
static int
processor_get_max_state(struct thermal_cooling_device *cdev,
                        unsigned long *state)
{
        struct acpi_device *device = cdev->devdata;
        struct acpi_processor *pr;

        if (!device)
                return -EINVAL;

        pr = acpi_driver_data(device);
        if (!pr)
                return -EINVAL;

        *state = acpi_processor_max_state(pr);
        return 0;
}

static int
processor_get_cur_state(struct thermal_cooling_device *cdev,
                        unsigned long *cur_state)
{
        struct acpi_device *device = cdev->devdata;
        struct acpi_processor *pr;

        if (!device)
                return -EINVAL;

        pr = acpi_driver_data(device);
        if (!pr)
                return -EINVAL;

        *cur_state = cpufreq_get_cur_state(pr->id);
        if (pr->flags.throttling)
                *cur_state += pr->throttling.state;
        return 0;
}

static int
processor_set_cur_state(struct thermal_cooling_device *cdev,
                        unsigned long state)
{
        struct acpi_device *device = cdev->devdata;
        struct acpi_processor *pr;
        int result = 0;
        int max_pstate;

        if (!device)
                return -EINVAL;

        pr = acpi_driver_data(device);
        if (!pr)
                return -EINVAL;

        max_pstate = cpufreq_get_max_state(pr->id);

        if (state > acpi_processor_max_state(pr))
                return -EINVAL;

        if (state <= max_pstate) {
                if (pr->flags.throttling && pr->throttling.state)
                        result = acpi_processor_set_throttling(pr, 0, false);
                cpufreq_set_cur_state(pr->id, state);
        } else {
                cpufreq_set_cur_state(pr->id, max_pstate);
                result = acpi_processor_set_throttling(pr,
                                state - max_pstate, false);
        }
        return result;
}

const struct thermal_cooling_device_ops processor_cooling_ops = {
        .get_max_state = processor_get_max_state,
        .get_cur_state = processor_get_cur_state,
        .set_cur_state = processor_set_cur_state,
};