// SPDX-License-Identifier: GPL-2.0-only
/*
 * intel_powerclamp.c - package c-state idle injection
 *
 * Copyright (c) 2012, Intel Corporation.
 *
 * Authors:
 *     Arjan van de Ven <arjan@linux.intel.com>
 *     Jacob Pan <jacob.jun.pan@linux.intel.com>
 *
 *      TODO:
 *           1. better handle wakeup from external interrupts, currently a fixed
 *              compensation is added to clamping duration when excessive amount
 *              of wakeups are observed during idle time. the reason is that in
 *              case of external interrupts without need for ack, clamping down
 *              cpu in non-irq context does not reduce irq. for majority of the
 *              cases, clamping down cpu does help reduce irq as well, we should
 *              be able to differentiate the two cases and give a quantitative
 *              solution for the irqs that we can control. perhaps based on
 *              get_cpu_iowait_time_us()
 *
 *           2. synchronization with other hw blocks
 */

#define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/cpu.h>
#include <linux/thermal.h>
#include <linux/slab.h>
#include <linux/tick.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/sched/rt.h>
#include <uapi/linux/sched/types.h>

#include <asm/nmi.h>
#include <asm/msr.h>
#include <asm/mwait.h>
#include <asm/cpu_device_id.h>
#include <asm/hardirq.h>

#define MAX_TARGET_RATIO (50U)
/* For each undisturbed clamping period (no extra wake ups during idle time),
 * we increment the confidence counter for the given target ratio.
 * CONFIDENCE_OK defines the level where runtime calibration results are
 * valid.
 */
#define CONFIDENCE_OK (3)
/* Default idle injection duration, driver adjust sleep time to meet target
 * idle ratio. Similar to frequency modulation.
 */
#define DEFAULT_DURATION_JIFFIES (6)

static unsigned int target_mwait;
static struct dentry *debug_dir;

/* user selected target */
static unsigned int set_target_ratio;
static unsigned int current_ratio;
static bool should_skip;
static bool reduce_irq;
static atomic_t idle_wakeup_counter;
static unsigned int control_cpu; /* The cpu assigned to collect stat and update
                                  * control parameters. default to BSP but BSP
                                  * can be offlined.
                                  */
static bool clamping;

static const struct sched_param sparam = {
        .sched_priority = MAX_USER_RT_PRIO / 2,
};
struct powerclamp_worker_data {
        struct kthread_worker *worker;
        struct kthread_work balancing_work;
        struct kthread_delayed_work idle_injection_work;
        unsigned int cpu;
        unsigned int count;
        unsigned int guard;
        unsigned int window_size_now;
        unsigned int target_ratio;
        unsigned int duration_jiffies;
        bool clamping;
};

static struct powerclamp_worker_data __percpu *worker_data;
static struct thermal_cooling_device *cooling_dev;
static unsigned long *cpu_clamping_mask;  /* bit map for tracking per cpu
                                           * clamping kthread worker
                                           */

static unsigned int duration;
static unsigned int pkg_cstate_ratio_cur;
static unsigned int window_size;

static int duration_set(const char *arg, const struct kernel_param *kp)
{
        int ret = 0;
        unsigned long new_duration;

        ret = kstrtoul(arg, 10, &new_duration);
        if (ret)
                goto exit;
        if (new_duration > 25 || new_duration < 6) {
                pr_err("Out of recommended range %lu, between 6-25ms\n",
                        new_duration);
                ret = -EINVAL;
        }

        duration = clamp(new_duration, 6ul, 25ul);
        smp_mb();

exit:

        return ret;
}

static const struct kernel_param_ops duration_ops = {
        .set = duration_set,
        .get = param_get_int,
};


module_param_cb(duration, &duration_ops, &duration, 0644);
MODULE_PARM_DESC(duration, "forced idle time for each attempt in msec.");

struct powerclamp_calibration_data {
        unsigned long confidence;  /* used for calibration, basically a counter
                                    * gets incremented each time a clamping
                                    * period is completed without extra wakeups
                                    * once that counter is reached given level,
                                    * compensation is deemed usable.
                                    */
        unsigned long steady_comp; /* steady state compensation used when
                                    * no extra wakeups occurred.
                                    */
        unsigned long dynamic_comp; /* compensate excessive wakeup from idle
                                     * mostly from external interrupts.
                                     */
};

static struct powerclamp_calibration_data cal_data[MAX_TARGET_RATIO];

static int window_size_set(const char *arg, const struct kernel_param *kp)
{
        int ret = 0;
        unsigned long new_window_size;

        ret = kstrtoul(arg, 10, &new_window_size);
        if (ret)
                goto exit_win;
        if (new_window_size > 10 || new_window_size < 2) {
                pr_err("Out of recommended window size %lu, between 2-10\n",
                        new_window_size);
                ret = -EINVAL;
        }

        window_size = clamp(new_window_size, 2ul, 10ul);
        smp_mb();

exit_win:

        return ret;
}

static const struct kernel_param_ops window_size_ops = {
        .set = window_size_set,
        .get = param_get_int,
};

module_param_cb(window_size, &window_size_ops, &window_size, 0644);
MODULE_PARM_DESC(window_size, "sliding window in number of clamping cycles\n"
        "\tpowerclamp controls idle ratio within this window. larger\n"
        "\twindow size results in slower response time but more smooth\n"
        "\tclamping results. default to 2.");

static void find_target_mwait(void)
{
        unsigned int eax, ebx, ecx, edx;
        unsigned int highest_cstate = 0;
        unsigned int highest_subcstate = 0;
        int i;

        if (boot_cpu_data.cpuid_level < CPUID_MWAIT_LEAF)
                return;

        cpuid(CPUID_MWAIT_LEAF, &eax, &ebx, &ecx, &edx);

        if (!(ecx & CPUID5_ECX_EXTENSIONS_SUPPORTED) ||
            !(ecx & CPUID5_ECX_INTERRUPT_BREAK))
                return;

        edx >>= MWAIT_SUBSTATE_SIZE;
        for (i = 0; i < 7 && edx; i++, edx >>= MWAIT_SUBSTATE_SIZE) {
                if (edx & MWAIT_SUBSTATE_MASK) {
                        highest_cstate = i;
                        highest_subcstate = edx & MWAIT_SUBSTATE_MASK;
                }
        }
        target_mwait = (highest_cstate << MWAIT_SUBSTATE_SIZE) |
                (highest_subcstate - 1);

}

struct pkg_cstate_info {
        bool skip;
        int msr_index;
        int cstate_id;
};

#define PKG_CSTATE_INIT(id) {                           \
                .msr_index = MSR_PKG_C##id##_RESIDENCY, \
                .cstate_id = id                         \
                        }

static struct pkg_cstate_info pkg_cstates[] = {
        PKG_CSTATE_INIT(2),
        PKG_CSTATE_INIT(3),
        PKG_CSTATE_INIT(6),
        PKG_CSTATE_INIT(7),
        PKG_CSTATE_INIT(8),
        PKG_CSTATE_INIT(9),
        PKG_CSTATE_INIT(10),
        {NULL},
};

static bool has_pkg_state_counter(void)
{
        u64 val;
        struct pkg_cstate_info *info = pkg_cstates;

        /* check if any one of the counter msrs exists */
        while (info->msr_index) {
                if (!rdmsrl_safe(info->msr_index, &val))
                        return true;
                info++;
        }

        return false;
}

static u64 pkg_state_counter(void)
{
        u64 val;
        u64 count = 0;
        struct pkg_cstate_info *info = pkg_cstates;

        while (info->msr_index) {
                if (!info->skip) {
                        if (!rdmsrl_safe(info->msr_index, &val))
                                count += val;
                        else
                                info->skip = true;
                }
                info++;
        }

        return count;
}

static unsigned int get_compensation(int ratio)
{
        unsigned int comp = 0;

        /* we only use compensation if all adjacent ones are good */
        if (ratio == 1 &&
                cal_data[ratio].confidence >= CONFIDENCE_OK &&
                cal_data[ratio + 1].confidence >= CONFIDENCE_OK &&
                cal_data[ratio + 2].confidence >= CONFIDENCE_OK) {
                comp = (cal_data[ratio].steady_comp +
                        cal_data[ratio + 1].steady_comp +
                        cal_data[ratio + 2].steady_comp) / 3;
        } else if (ratio == MAX_TARGET_RATIO - 1 &&
                cal_data[ratio].confidence >= CONFIDENCE_OK &&
                cal_data[ratio - 1].confidence >= CONFIDENCE_OK &&
                cal_data[ratio - 2].confidence >= CONFIDENCE_OK) {
                comp = (cal_data[ratio].steady_comp +
                        cal_data[ratio - 1].steady_comp +
                        cal_data[ratio - 2].steady_comp) / 3;
        } else if (cal_data[ratio].confidence >= CONFIDENCE_OK &&
                cal_data[ratio - 1].confidence >= CONFIDENCE_OK &&
                cal_data[ratio + 1].confidence >= CONFIDENCE_OK) {
                comp = (cal_data[ratio].steady_comp +
                        cal_data[ratio - 1].steady_comp +
                        cal_data[ratio + 1].steady_comp) / 3;
        }

        /* REVISIT: simple penalty of double idle injection */
        if (reduce_irq)
                comp = ratio;
        /* do not exceed limit */
        if (comp + ratio >= MAX_TARGET_RATIO)
                comp = MAX_TARGET_RATIO - ratio - 1;

        return comp;
}

static void adjust_compensation(int target_ratio, unsigned int win)
{
        int delta;
        struct powerclamp_calibration_data *d = &cal_data[target_ratio];

        /*
         * adjust compensations if confidence level has not been reached or
         * there are too many wakeups during the last idle injection period, we
         * cannot trust the data for compensation.
         */
        if (d->confidence >= CONFIDENCE_OK ||
                atomic_read(&idle_wakeup_counter) >
                win * num_online_cpus())
                return;

        delta = set_target_ratio - current_ratio;
        /* filter out bad data */
        if (delta >= 0 && delta <= (1+target_ratio/10)) {
                if (d->steady_comp)
                        d->steady_comp =
                                roundup(delta+d->steady_comp, 2)/2;
                else
                        d->steady_comp = delta;
                d->confidence++;
        }
}

static bool powerclamp_adjust_controls(unsigned int target_ratio,
                                unsigned int guard, unsigned int win)
{
        static u64 msr_last, tsc_last;
        u64 msr_now, tsc_now;
        u64 val64;

        /* check result for the last window */
        msr_now = pkg_state_counter();
        tsc_now = rdtsc();

        /* calculate pkg cstate vs tsc ratio */
        if (!msr_last || !tsc_last)
                current_ratio = 1;
        else if (tsc_now-tsc_last) {
                val64 = 100*(msr_now-msr_last);
                do_div(val64, (tsc_now-tsc_last));
                current_ratio = val64;
        }

        /* update record */
        msr_last = msr_now;
        tsc_last = tsc_now;

        adjust_compensation(target_ratio, win);
        /*
         * too many external interrupts, set flag such
         * that we can take measure later.
         */
        reduce_irq = atomic_read(&idle_wakeup_counter) >=
                2 * win * num_online_cpus();

        atomic_set(&idle_wakeup_counter, 0);
        /* if we are above target+guard, skip */
        return set_target_ratio + guard <= current_ratio;
}

static void clamp_balancing_func(struct kthread_work *work)
{
        struct powerclamp_worker_data *w_data;
        int sleeptime;
        unsigned long target_jiffies;
        unsigned int compensated_ratio;
        int interval; /* jiffies to sleep for each attempt */

        w_data = container_of(work, struct powerclamp_worker_data,
                              balancing_work);

        /*
         * make sure user selected ratio does not take effect until
         * the next round. adjust target_ratio if user has changed
         * target such that we can converge quickly.
         */
        w_data->target_ratio = READ_ONCE(set_target_ratio);
        w_data->guard = 1 + w_data->target_ratio / 20;
        w_data->window_size_now = window_size;
        w_data->duration_jiffies = msecs_to_jiffies(duration);
        w_data->count++;

        /*
         * systems may have different ability to enter package level
         * c-states, thus we need to compensate the injected idle ratio
         * to achieve the actual target reported by the HW.
         */
        compensated_ratio = w_data->target_ratio +
                get_compensation(w_data->target_ratio);
        if (compensated_ratio <= 0)
                compensated_ratio = 1;
        interval = w_data->duration_jiffies * 100 / compensated_ratio;

        /* align idle time */
        target_jiffies = roundup(jiffies, interval);
        sleeptime = target_jiffies - jiffies;
        if (sleeptime <= 0)
                sleeptime = 1;

        if (clamping && w_data->clamping && cpu_online(w_data->cpu))
                kthread_queue_delayed_work(w_data->worker,
                                           &w_data->idle_injection_work,
                                           sleeptime);
}

static void clamp_idle_injection_func(struct kthread_work *work)
{
        struct powerclamp_worker_data *w_data;

        w_data = container_of(work, struct powerclamp_worker_data,
                              idle_injection_work.work);

        /*
         * only elected controlling cpu can collect stats and update
         * control parameters.
         */
        if (w_data->cpu == control_cpu &&
            !(w_data->count % w_data->window_size_now)) {
                should_skip =
                        powerclamp_adjust_controls(w_data->target_ratio,
                                                   w_data->guard,
                                                   w_data->window_size_now);
                smp_mb();
        }

        if (should_skip)
                goto balance;

        play_idle(jiffies_to_usecs(w_data->duration_jiffies));

balance:
        if (clamping && w_data->clamping && cpu_online(w_data->cpu))
                kthread_queue_work(w_data->worker, &w_data->balancing_work);
}

/*
 * 1 HZ polling while clamping is active, useful for userspace
 * to monitor actual idle ratio.
 */
static void poll_pkg_cstate(struct work_struct *dummy);
static DECLARE_DELAYED_WORK(poll_pkg_cstate_work, poll_pkg_cstate);
static void poll_pkg_cstate(struct work_struct *dummy)
{
        static u64 msr_last;
        static u64 tsc_last;

        u64 msr_now;
        u64 tsc_now;
        u64 val64;

        msr_now = pkg_state_counter();
        tsc_now = rdtsc();

        /* calculate pkg cstate vs tsc ratio */
        if (!msr_last || !tsc_last)
                pkg_cstate_ratio_cur = 1;
        else {
                if (tsc_now - tsc_last) {
                        val64 = 100 * (msr_now - msr_last);
                        do_div(val64, (tsc_now - tsc_last));
                        pkg_cstate_ratio_cur = val64;
                }
        }

        /* update record */
        msr_last = msr_now;
        tsc_last = tsc_now;

        if (true == clamping)
                schedule_delayed_work(&poll_pkg_cstate_work, HZ);
}

static void start_power_clamp_worker(unsigned long cpu)
{
        struct powerclamp_worker_data *w_data = per_cpu_ptr(worker_data, cpu);
        struct kthread_worker *worker;

        worker = kthread_create_worker_on_cpu(cpu, 0, "kidle_inj/%ld", cpu);
        if (IS_ERR(worker))
                return;

        w_data->worker = worker;
        w_data->count = 0;
        w_data->cpu = cpu;
        w_data->clamping = true;
        set_bit(cpu, cpu_clamping_mask);
        sched_setscheduler(worker->task, SCHED_FIFO, &sparam);
        kthread_init_work(&w_data->balancing_work, clamp_balancing_func);
        kthread_init_delayed_work(&w_data->idle_injection_work,
                                  clamp_idle_injection_func);
        kthread_queue_work(w_data->worker, &w_data->balancing_work);
}

static void stop_power_clamp_worker(unsigned long cpu)
{
        struct powerclamp_worker_data *w_data = per_cpu_ptr(worker_data, cpu);

        if (!w_data->worker)
                return;

        w_data->clamping = false;
        /*
         * Make sure that all works that get queued after this point see
         * the clamping disabled. The counter part is not needed because
         * there is an implicit memory barrier when the queued work
         * is proceed.
         */
        smp_wmb();
        kthread_cancel_work_sync(&w_data->balancing_work);
        kthread_cancel_delayed_work_sync(&w_data->idle_injection_work);
        /*
         * The balancing work still might be queued here because
         * the handling of the "clapming" variable, cancel, and queue
         * operations are not synchronized via a lock. But it is not
         * a big deal. The balancing work is fast and destroy kthread
         * will wait for it.
         */
        clear_bit(w_data->cpu, cpu_clamping_mask);
        kthread_destroy_worker(w_data->worker);

        w_data->worker = NULL;
}

static int start_power_clamp(void)
{
        unsigned long cpu;

        set_target_ratio = clamp(set_target_ratio, 0U, MAX_TARGET_RATIO - 1);
        /* prevent cpu hotplug */
        get_online_cpus();

        /* prefer BSP */
        control_cpu = 0;
        if (!cpu_online(control_cpu))
                control_cpu = smp_processor_id();

        clamping = true;
        schedule_delayed_work(&poll_pkg_cstate_work, 0);

        /* start one kthread worker per online cpu */
        for_each_online_cpu(cpu) {
                start_power_clamp_worker(cpu);
        }
        put_online_cpus();

        return 0;
}

static void end_power_clamp(void)
{
        int i;

        /*
         * Block requeuing in all the kthread workers. They will flush and
         * stop faster.
         */
        clamping = false;
        if (bitmap_weight(cpu_clamping_mask, num_possible_cpus())) {
                for_each_set_bit(i, cpu_clamping_mask, num_possible_cpus()) {
                        pr_debug("clamping worker for cpu %d alive, destroy\n",
                                 i);
                        stop_power_clamp_worker(i);
                }
        }
}

static int powerclamp_cpu_online(unsigned int cpu)
{
        if (clamping == false)
                return 0;
        start_power_clamp_worker(cpu);
        /* prefer BSP as controlling CPU */
        if (cpu == 0) {
                control_cpu = 0;
                smp_mb();
        }
        return 0;
}

static int powerclamp_cpu_predown(unsigned int cpu)
{
        if (clamping == false)
                return 0;

        stop_power_clamp_worker(cpu);
        if (cpu != control_cpu)
                return 0;

        control_cpu = cpumask_first(cpu_online_mask);
        if (control_cpu == cpu)
                control_cpu = cpumask_next(cpu, cpu_online_mask);
        smp_mb();
        return 0;
}

static int powerclamp_get_max_state(struct thermal_cooling_device *cdev,
                                 unsigned long *state)
{
        *state = MAX_TARGET_RATIO;

        return 0;
}

static int powerclamp_get_cur_state(struct thermal_cooling_device *cdev,
                                 unsigned long *state)
{
        if (true == clamping)
                *state = pkg_cstate_ratio_cur;
        else
                /* to save power, do not poll idle ratio while not clamping */
                *state = -1; /* indicates invalid state */

        return 0;
}

static int powerclamp_set_cur_state(struct thermal_cooling_device *cdev,
                                 unsigned long new_target_ratio)
{
        int ret = 0;

        new_target_ratio = clamp(new_target_ratio, 0UL,
                                (unsigned long) (MAX_TARGET_RATIO-1));
        if (set_target_ratio == 0 && new_target_ratio > 0) {
                pr_info("Start idle injection to reduce power\n");
                set_target_ratio = new_target_ratio;
                ret = start_power_clamp();
                goto exit_set;
        } else  if (set_target_ratio > 0 && new_target_ratio == 0) {
                pr_info("Stop forced idle injection\n");
                end_power_clamp();
                set_target_ratio = 0;
        } else  /* adjust currently running */ {
                set_target_ratio = new_target_ratio;
                /* make new set_target_ratio visible to other cpus */
                smp_mb();
        }

exit_set:
        return ret;
}

/* bind to generic thermal layer as cooling device*/
static struct thermal_cooling_device_ops powerclamp_cooling_ops = {
        .get_max_state = powerclamp_get_max_state,
        .get_cur_state = powerclamp_get_cur_state,
        .set_cur_state = powerclamp_set_cur_state,
};

static const struct x86_cpu_id __initconst intel_powerclamp_ids[] = {
        { X86_VENDOR_INTEL, X86_FAMILY_ANY, X86_MODEL_ANY, X86_FEATURE_MWAIT },
        {}
};
MODULE_DEVICE_TABLE(x86cpu, intel_powerclamp_ids);

static int __init powerclamp_probe(void)
{

        if (!x86_match_cpu(intel_powerclamp_ids)) {
                pr_err("CPU does not support MWAIT\n");
                return -ENODEV;
        }

        /* The goal for idle time alignment is to achieve package cstate. */
        if (!has_pkg_state_counter()) {
                pr_info("No package C-state available\n");
                return -ENODEV;
        }

        /* find the deepest mwait value */
        find_target_mwait();

        return 0;
}

static int powerclamp_debug_show(struct seq_file *m, void *unused)
{
        int i = 0;

        seq_printf(m, "controlling cpu: %d\n", control_cpu);
        seq_printf(m, "pct confidence steady dynamic (compensation)\n");
        for (i = 0; i < MAX_TARGET_RATIO; i++) {
                seq_printf(m, "%d\t%lu\t%lu\t%lu\n",
                        i,
                        cal_data[i].confidence,
                        cal_data[i].steady_comp,
                        cal_data[i].dynamic_comp);
        }

        return 0;
}

DEFINE_SHOW_ATTRIBUTE(powerclamp_debug);

static inline void powerclamp_create_debug_files(void)
{
        debug_dir = debugfs_create_dir("intel_powerclamp", NULL);

        debugfs_create_file("powerclamp_calib", S_IRUGO, debug_dir, cal_data,
                            &powerclamp_debug_fops);
}

static enum cpuhp_state hp_state;

static int __init powerclamp_init(void)
{
        int retval;
        int bitmap_size;

        bitmap_size = BITS_TO_LONGS(num_possible_cpus()) * sizeof(long);
        cpu_clamping_mask = kzalloc(bitmap_size, GFP_KERNEL);
        if (!cpu_clamping_mask)
                return -ENOMEM;

        /* probe cpu features and ids here */
        retval = powerclamp_probe();
        if (retval)
                goto exit_free;

        /* set default limit, maybe adjusted during runtime based on feedback */
        window_size = 2;
        retval = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
                                           "thermal/intel_powerclamp:online",
                                           powerclamp_cpu_online,
                                           powerclamp_cpu_predown);
        if (retval < 0)
                goto exit_free;

        hp_state = retval;

        worker_data = alloc_percpu(struct powerclamp_worker_data);
        if (!worker_data) {
                retval = -ENOMEM;
                goto exit_unregister;
        }

        cooling_dev = thermal_cooling_device_register("intel_powerclamp", NULL,
                                                &powerclamp_cooling_ops);
        if (IS_ERR(cooling_dev)) {
                retval = -ENODEV;
                goto exit_free_thread;
        }

        if (!duration)
                duration = jiffies_to_msecs(DEFAULT_DURATION_JIFFIES);

        powerclamp_create_debug_files();

        return 0;

exit_free_thread:
        free_percpu(worker_data);
exit_unregister:
        cpuhp_remove_state_nocalls(hp_state);
exit_free:
        kfree(cpu_clamping_mask);
        return retval;
}
module_init(powerclamp_init);

static void __exit powerclamp_exit(void)
{
        end_power_clamp();
        cpuhp_remove_state_nocalls(hp_state);
        free_percpu(worker_data);
        thermal_cooling_device_unregister(cooling_dev);
        kfree(cpu_clamping_mask);

        cancel_delayed_work_sync(&poll_pkg_cstate_work);
        debugfs_remove_recursive(debug_dir);
}
module_exit(powerclamp_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Arjan van de Ven <arjan@linux.intel.com>");
MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@linux.intel.com>");
MODULE_DESCRIPTION("Package Level C-state Idle Injection for Intel CPUs");