rtctimer.c

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/*
 *  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 <linux/init.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/log2.h>
#include <sound/core.h>
#include <sound/timer.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(struct snd_timer *t);
static int rtctimer_close(struct snd_timer *t);
static int rtctimer_start(struct snd_timer *t);
static int rtctimer_stop(struct snd_timer *t);


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

static int rtctimer_freq = RTC_FREQ;        /* frequency */
static struct snd_timer *rtctimer;
static struct tasklet_struct rtc_tasklet;
static rtc_task_t rtc_task;


static int
rtctimer_open(struct snd_timer *t)
{
    int err;

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

static int
rtctimer_close(struct snd_timer *t)
{
    rtc_task_t *rtc = t->private_data;
    if (rtc) {
        rtc_unregister(rtc);
        tasklet_kill(&rtc_tasklet);
        t->private_data = NULL;
    }
    return 0;
}

static int
rtctimer_start(struct snd_timer *timer)
{
    rtc_task_t *rtc = timer->private_data;
    if (snd_BUG_ON(!rtc))
        return -EINVAL;
    rtc_control(rtc, RTC_IRQP_SET, rtctimer_freq);
    rtc_control(rtc, RTC_PIE_ON, 0);
    return 0;
}

static int
rtctimer_stop(struct snd_timer *timer)
{
    rtc_task_t *rtc = timer->private_data;
    if (snd_BUG_ON(!rtc))
        return -EINVAL;
    rtc_control(rtc, RTC_PIE_OFF, 0);
    return 0;
}

static void rtctimer_tasklet(unsigned long data)
{
    snd_timer_interrupt((struct snd_timer *)data, 1);
}

/*
 * interrupt
 */
static void rtctimer_interrupt(void *private_data)
{
    tasklet_schedule(private_data);
}


/*
 *  ENTRY functions
 */
static int __init rtctimer_init(void)
{
    int err;
    struct snd_timer *timer;

    if (rtctimer_freq < 2 || rtctimer_freq > 8192 ||
        !is_power_of_2(rtctimer_freq)) {
        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;

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

    tasklet_init(&rtc_tasklet, rtctimer_tasklet, (unsigned long)timer);

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

    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_free(rtctimer);
        rtctimer = NULL;
    }
}


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

module_param(rtctimer_freq, int, 0444);
MODULE_PARM_DESC(rtctimer_freq, "timer frequency in Hz");

MODULE_LICENSE("GPL");

MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_RTC));

#endif /* CONFIG_RTC || CONFIG_RTC_MODULE */