cttimer.c

Go to the documentation of this file.

/*
 * PCM timer handling on ctxfi
 *
 * This source file is released under GPL v2 license (no other versions).
 * See the COPYING file included in the main directory of this source
 * distribution for the license terms and conditions.
 */

#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, S_IRUGO);

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;
    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(unsigned long data)
{
    struct ct_timer_instance *ti = (struct ct_timer_instance *)data;
    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)
{
    setup_timer(&ti->timer, ct_systimer_callback,
            (unsigned long)ti);
}

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 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 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) {
        snd_printd(KERN_INFO "ctxfi: Use xfi-native timer\n");
        atimer->ops = &ct_xfitimer_ops;
        hw->irq_callback_data = atimer;
        hw->irq_callback = ct_timer_interrupt;
    } else {
        snd_printd(KERN_INFO "ctxfi: 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);
}