// SPDX-License-Identifier: GPL-2.0-only
/*
 * PCM timer handling on ctxfi
 */

#include <linux/slab.h>
#include <linux/math64.h>
#include <linux/moduleparam.h>
#include <sound/core.h>
#include <sound/pcm.h>
#include "ctatc.h"
#include "cthardware.h"
#include "cttimer.h"

static bool use_system_timer;
MODULE_PARM_DESC(use_system_timer, "Force to use system-timer");
module_param(use_system_timer, bool, 0444);

struct ct_timer_ops {
        void (*init)(struct ct_timer_instance *);
        void (*prepare)(struct ct_timer_instance *);
        void (*start)(struct ct_timer_instance *);
        void (*stop)(struct ct_timer_instance *);
        void (*free_instance)(struct ct_timer_instance *);
        void (*interrupt)(struct ct_timer *);
        void (*free_global)(struct ct_timer *);
};

/* timer instance -- assigned to each PCM stream */
struct ct_timer_instance {
        spinlock_t lock;
        struct ct_timer *timer_base;
        struct ct_atc_pcm *apcm;
        struct snd_pcm_substream *substream;
        struct timer_list timer;
        struct list_head instance_list;
        struct list_head running_list;
        unsigned int position;
        unsigned int frag_count;
        unsigned int running:1;
        unsigned int need_update:1;
};

/* timer instance manager */
struct ct_timer {
        spinlock_t lock;                /* global timer lock (for xfitimer) */
        spinlock_t list_lock;           /* lock for instance list */
        struct ct_atc *atc;
        const struct ct_timer_ops *ops;
        struct list_head instance_head;
        struct list_head running_head;
        unsigned int wc;                /* current wallclock */
        unsigned int irq_handling:1;    /* in IRQ handling */
        unsigned int reprogram:1;       /* need to reprogram the internval */
        unsigned int running:1;         /* global timer running */
};


/*
 * system-timer-based updates
 */

static void ct_systimer_callback(struct timer_list *t)
{
        struct ct_timer_instance *ti = from_timer(ti, t, timer);
        struct snd_pcm_substream *substream = ti->substream;
        struct snd_pcm_runtime *runtime = substream->runtime;
        struct ct_atc_pcm *apcm = ti->apcm;
        unsigned int period_size = runtime->period_size;
        unsigned int buffer_size = runtime->buffer_size;
        unsigned long flags;
        unsigned int position, dist, interval;

        position = substream->ops->pointer(substream);
        dist = (position + buffer_size - ti->position) % buffer_size;
        if (dist >= period_size ||
            position / period_size != ti->position / period_size) {
                apcm->interrupt(apcm);
                ti->position = position;
        }
        /* Add extra HZ*5/1000 to avoid overrun issue when recording
         * at 8kHz in 8-bit format or at 88kHz in 24-bit format. */
        interval = ((period_size - (position % period_size))
                   * HZ + (runtime->rate - 1)) / runtime->rate + HZ * 5 / 1000;
        spin_lock_irqsave(&ti->lock, flags);
        if (ti->running)
                mod_timer(&ti->timer, jiffies + interval);
        spin_unlock_irqrestore(&ti->lock, flags);
}

static void ct_systimer_init(struct ct_timer_instance *ti)
{
        timer_setup(&ti->timer, ct_systimer_callback, 0);
}

static void ct_systimer_start(struct ct_timer_instance *ti)
{
        struct snd_pcm_runtime *runtime = ti->substream->runtime;
        unsigned long flags;

        spin_lock_irqsave(&ti->lock, flags);
        ti->running = 1;
        mod_timer(&ti->timer,
                  jiffies + (runtime->period_size * HZ +
                             (runtime->rate - 1)) / runtime->rate);
        spin_unlock_irqrestore(&ti->lock, flags);
}

static void ct_systimer_stop(struct ct_timer_instance *ti)
{
        unsigned long flags;

        spin_lock_irqsave(&ti->lock, flags);
        ti->running = 0;
        del_timer(&ti->timer);
        spin_unlock_irqrestore(&ti->lock, flags);
}

static void ct_systimer_prepare(struct ct_timer_instance *ti)
{
        ct_systimer_stop(ti);
        try_to_del_timer_sync(&ti->timer);
}

#define ct_systimer_free        ct_systimer_prepare

static const struct ct_timer_ops ct_systimer_ops = {
        .init = ct_systimer_init,
        .free_instance = ct_systimer_free,
        .prepare = ct_systimer_prepare,
        .start = ct_systimer_start,
        .stop = ct_systimer_stop,
};


/*
 * Handling multiple streams using a global emu20k1 timer irq
 */

#define CT_TIMER_FREQ   48000
#define MIN_TICKS       1
#define MAX_TICKS       ((1 << 13) - 1)

static void ct_xfitimer_irq_rearm(struct ct_timer *atimer, int ticks)
{
        struct hw *hw = atimer->atc->hw;
        if (ticks > MAX_TICKS)
                ticks = MAX_TICKS;
        hw->set_timer_tick(hw, ticks);
        if (!atimer->running)
                hw->set_timer_irq(hw, 1);
        atimer->running = 1;
}

static void ct_xfitimer_irq_stop(struct ct_timer *atimer)
{
        if (atimer->running) {
                struct hw *hw = atimer->atc->hw;
                hw->set_timer_irq(hw, 0);
                hw->set_timer_tick(hw, 0);
                atimer->running = 0;
        }
}

static inline unsigned int ct_xfitimer_get_wc(struct ct_timer *atimer)
{
        struct hw *hw = atimer->atc->hw;
        return hw->get_wc(hw);
}

/*
 * reprogram the timer interval;
 * checks the running instance list and determines the next timer interval.
 * also updates the each stream position, returns the number of streams
 * to call snd_pcm_period_elapsed() appropriately
 *
 * call this inside the lock and irq disabled
 */
static int ct_xfitimer_reprogram(struct ct_timer *atimer, int can_update)
{
        struct ct_timer_instance *ti;
        unsigned int min_intr = (unsigned int)-1;
        int updates = 0;
        unsigned int wc, diff;

        if (list_empty(&atimer->running_head)) {
                ct_xfitimer_irq_stop(atimer);
                atimer->reprogram = 0; /* clear flag */
                return 0;
        }

        wc = ct_xfitimer_get_wc(atimer);
        diff = wc - atimer->wc;
        atimer->wc = wc;
        list_for_each_entry(ti, &atimer->running_head, running_list) {
                if (ti->frag_count > diff)
                        ti->frag_count -= diff;
                else {
                        unsigned int pos;
                        unsigned int period_size, rate;

                        period_size = ti->substream->runtime->period_size;
                        rate = ti->substream->runtime->rate;
                        pos = ti->substream->ops->pointer(ti->substream);
                        if (pos / period_size != ti->position / period_size) {
                                ti->need_update = 1;
                                ti->position = pos;
                                updates++;
                        }
                        pos %= period_size;
                        pos = period_size - pos;
                        ti->frag_count = div_u64((u64)pos * CT_TIMER_FREQ +
                                                 rate - 1, rate);
                }
                if (ti->need_update && !can_update)
                        min_intr = 0; /* pending to the next irq */
                if (ti->frag_count < min_intr)
                        min_intr = ti->frag_count;
        }

        if (min_intr < MIN_TICKS)
                min_intr = MIN_TICKS;
        ct_xfitimer_irq_rearm(atimer, min_intr);
        atimer->reprogram = 0; /* clear flag */
        return updates;
}

/* look through the instance list and call period_elapsed if needed */
static void ct_xfitimer_check_period(struct ct_timer *atimer)
{
        struct ct_timer_instance *ti;
        unsigned long flags;

        spin_lock_irqsave(&atimer->list_lock, flags);
        list_for_each_entry(ti, &atimer->instance_head, instance_list) {
                if (ti->running && ti->need_update) {
                        ti->need_update = 0;
                        ti->apcm->interrupt(ti->apcm);
                }
        }
        spin_unlock_irqrestore(&atimer->list_lock, flags);
}

/* Handle timer-interrupt */
static void ct_xfitimer_callback(struct ct_timer *atimer)
{
        int update;
        unsigned long flags;

        spin_lock_irqsave(&atimer->lock, flags);
        atimer->irq_handling = 1;
        do {
                update = ct_xfitimer_reprogram(atimer, 1);
                spin_unlock(&atimer->lock);
                if (update)
                        ct_xfitimer_check_period(atimer);
                spin_lock(&atimer->lock);
        } while (atimer->reprogram);
        atimer->irq_handling = 0;
        spin_unlock_irqrestore(&atimer->lock, flags);
}

static void ct_xfitimer_prepare(struct ct_timer_instance *ti)
{
        ti->frag_count = ti->substream->runtime->period_size;
        ti->running = 0;
        ti->need_update = 0;
}


/* start/stop the timer */
static void ct_xfitimer_update(struct ct_timer *atimer)
{
        unsigned long flags;

        spin_lock_irqsave(&atimer->lock, flags);
        if (atimer->irq_handling) {
                /* reached from IRQ handler; let it handle later */
                atimer->reprogram = 1;
                spin_unlock_irqrestore(&atimer->lock, flags);
                return;
        }

        ct_xfitimer_irq_stop(atimer);
        ct_xfitimer_reprogram(atimer, 0);
        spin_unlock_irqrestore(&atimer->lock, flags);
}

static void ct_xfitimer_start(struct ct_timer_instance *ti)
{
        struct ct_timer *atimer = ti->timer_base;
        unsigned long flags;

        spin_lock_irqsave(&atimer->lock, flags);
        if (list_empty(&ti->running_list))
                atimer->wc = ct_xfitimer_get_wc(atimer);
        ti->running = 1;
        ti->need_update = 0;
        list_add(&ti->running_list, &atimer->running_head);
        spin_unlock_irqrestore(&atimer->lock, flags);
        ct_xfitimer_update(atimer);
}

static void ct_xfitimer_stop(struct ct_timer_instance *ti)
{
        struct ct_timer *atimer = ti->timer_base;
        unsigned long flags;

        spin_lock_irqsave(&atimer->lock, flags);
        list_del_init(&ti->running_list);
        ti->running = 0;
        spin_unlock_irqrestore(&atimer->lock, flags);
        ct_xfitimer_update(atimer);
}

static void ct_xfitimer_free_global(struct ct_timer *atimer)
{
        ct_xfitimer_irq_stop(atimer);
}

static const struct ct_timer_ops ct_xfitimer_ops = {
        .prepare = ct_xfitimer_prepare,
        .start = ct_xfitimer_start,
        .stop = ct_xfitimer_stop,
        .interrupt = ct_xfitimer_callback,
        .free_global = ct_xfitimer_free_global,
};

/*
 * timer instance
 */

struct ct_timer_instance *
ct_timer_instance_new(struct ct_timer *atimer, struct ct_atc_pcm *apcm)
{
        struct ct_timer_instance *ti;

        ti = kzalloc(sizeof(*ti), GFP_KERNEL);
        if (!ti)
                return NULL;
        spin_lock_init(&ti->lock);
        INIT_LIST_HEAD(&ti->instance_list);
        INIT_LIST_HEAD(&ti->running_list);
        ti->timer_base = atimer;
        ti->apcm = apcm;
        ti->substream = apcm->substream;
        if (atimer->ops->init)
                atimer->ops->init(ti);

        spin_lock_irq(&atimer->list_lock);
        list_add(&ti->instance_list, &atimer->instance_head);
        spin_unlock_irq(&atimer->list_lock);

        return ti;
}

void ct_timer_prepare(struct ct_timer_instance *ti)
{
        if (ti->timer_base->ops->prepare)
                ti->timer_base->ops->prepare(ti);
        ti->position = 0;
        ti->running = 0;
}

void ct_timer_start(struct ct_timer_instance *ti)
{
        struct ct_timer *atimer = ti->timer_base;
        atimer->ops->start(ti);
}

void ct_timer_stop(struct ct_timer_instance *ti)
{
        struct ct_timer *atimer = ti->timer_base;
        atimer->ops->stop(ti);
}

void ct_timer_instance_free(struct ct_timer_instance *ti)
{
        struct ct_timer *atimer = ti->timer_base;

        atimer->ops->stop(ti); /* to be sure */
        if (atimer->ops->free_instance)
                atimer->ops->free_instance(ti);

        spin_lock_irq(&atimer->list_lock);
        list_del(&ti->instance_list);
        spin_unlock_irq(&atimer->list_lock);

        kfree(ti);
}

/*
 * timer manager
 */

static void ct_timer_interrupt(void *data, unsigned int status)
{
        struct ct_timer *timer = data;

        /* Interval timer interrupt */
        if ((status & IT_INT) && timer->ops->interrupt)
                timer->ops->interrupt(timer);
}

struct ct_timer *ct_timer_new(struct ct_atc *atc)
{
        struct ct_timer *atimer;
        struct hw *hw;

        atimer = kzalloc(sizeof(*atimer), GFP_KERNEL);
        if (!atimer)
                return NULL;
        spin_lock_init(&atimer->lock);
        spin_lock_init(&atimer->list_lock);
        INIT_LIST_HEAD(&atimer->instance_head);
        INIT_LIST_HEAD(&atimer->running_head);
        atimer->atc = atc;
        hw = atc->hw;
        if (!use_system_timer && hw->set_timer_irq) {
                dev_info(atc->card->dev, "Use xfi-native timer\n");
                atimer->ops = &ct_xfitimer_ops;
                hw->irq_callback_data = atimer;
                hw->irq_callback = ct_timer_interrupt;
        } else {
                dev_info(atc->card->dev, "Use system timer\n");
                atimer->ops = &ct_systimer_ops;
        }
        return atimer;
}

void ct_timer_free(struct ct_timer *atimer)
{
        struct hw *hw = atimer->atc->hw;
        hw->irq_callback = NULL;
        if (atimer->ops->free_global)
                atimer->ops->free_global(atimer);
        kfree(atimer);
}