source: GPL/branches/alsa-resync1/alsa-kernel/core/rtctimer.c@ 224

/*
 *  RTC based high-frequency timer
 *
 *  Copyright (C) 2000 Takashi Iwai
 *      based on rtctimer.c by Steve Ratcliffe
 *
 *   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.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 *
 */

#include <sound/driver.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/threads.h>
#include <linux/interrupt.h>
#include <sound/core.h>
#include <sound/timer.h>
#include <sound/info.h>

#if defined(CONFIG_RTC) || defined(CONFIG_RTC_MODULE)

#include <linux/mc146818rtc.h>

#define RTC_FREQ        1024            /* default frequency */
#define NANO_SEC        1000000000L     /* 10^9 in sec */

/*
 * prototypes
 */
static int rtctimer_open(snd_timer_t *t);
static int rtctimer_close(snd_timer_t *t);
static int rtctimer_start(snd_timer_t *t);
static int rtctimer_stop(snd_timer_t *t);


/*
 * The hardware dependent description for this timer.
 */
static struct _snd_timer_hardware rtc_hw = {
        .flags =        SNDRV_TIMER_HW_FIRST|SNDRV_TIMER_HW_AUTO,
        .ticks =        100000000L,             /* FIXME: XXX */
        .open =         rtctimer_open,
        .close =        rtctimer_close,
        .start =        rtctimer_start,
        .stop =         rtctimer_stop,
};

int rtctimer_freq = RTC_FREQ;           /* frequency */
static snd_timer_t *rtctimer;
static atomic_t rtc_inc = ATOMIC_INIT(0);
static rtc_task_t rtc_task;


static int
rtctimer_open(snd_timer_t *t)
{
        int err;

        err = rtc_register(&rtc_task);
        if (err < 0)
                return err;
        t->private_data = &rtc_task;
        return 0;
}

static int
rtctimer_close(snd_timer_t *t)
{
        rtc_task_t *rtc = t->private_data;
        if (rtc) {
                rtc_unregister(rtc);
                t->private_data = NULL;
        }
        return 0;
}

static int
rtctimer_start(snd_timer_t *timer)
{
        rtc_task_t *rtc = timer->private_data;
        snd_assert(rtc != NULL, return -EINVAL);
        rtc_control(rtc, RTC_IRQP_SET, rtctimer_freq);
        rtc_control(rtc, RTC_PIE_ON, 0);
        atomic_set(&rtc_inc, 0);
        return 0;
}

static int
rtctimer_stop(snd_timer_t *timer)
{
        rtc_task_t *rtc = timer->private_data;
        snd_assert(rtc != NULL, return -EINVAL);
        rtc_control(rtc, RTC_PIE_OFF, 0);
        return 0;
}

/*
 * interrupt
 */
static void rtctimer_interrupt(void *private_data)
{
        int ticks;

        atomic_inc(&rtc_inc);
        ticks = atomic_read(&rtc_inc);
                snd_timer_interrupt((snd_timer_t*)private_data, ticks);
                atomic_sub(ticks, &rtc_inc);
        }


/*
 *  ENTRY functions
 */
static int __init rtctimer_init(void)
{
        int order, err;
        snd_timer_t *timer;

        if (rtctimer_freq < 2 || rtctimer_freq > 8192) {
                snd_printk(KERN_ERR "rtctimer: invalid frequency %d\n", rtctimer_freq);
                return -EINVAL;
        }
        for (order = 1; rtctimer_freq > order; order <<= 1)
                ;
        if (rtctimer_freq != order) {
                snd_printk(KERN_ERR "rtctimer: invalid frequency %d\n", rtctimer_freq);
                return -EINVAL;
        }

        /* Create a new timer and set up the fields */
        err = snd_timer_global_new("rtc", SNDRV_TIMER_GLOBAL_RTC, &timer);
        if (err < 0)
                return err;

        strcpy(timer->name, "RTC timer");
        timer->hw = rtc_hw;
        timer->hw.resolution = NANO_SEC / rtctimer_freq;

        /* set up RTC callback */
        rtc_task.func = rtctimer_interrupt;
        rtc_task.private_data = timer;

        err = snd_timer_global_register(timer);
        if (err < 0) {
                snd_timer_global_free(timer);
                return err;
        }
        rtctimer = timer; /* remember this */

        return 0;
}

static void __exit rtctimer_exit(void)
{
        if (rtctimer) {
                snd_timer_global_unregister(rtctimer);
                rtctimer = NULL;
        }
}


/*
 * exported stuff
 */
module_init(rtctimer_init)
module_exit(rtctimer_exit)

MODULE_PARM(rtctimer_freq, "i");
MODULE_PARM_DESC(rtctimer_freq, "timer frequency in Hz");

MODULE_LICENSE("GPL");

#endif /* CONFIG_RTC || CONFIG_RTC_MODULE */