LXR linux/sound/core/hrtimer.c

   1/*
   2 * ALSA timer back-end using hrtimer
   3 * Copyright (C) 2008 Takashi Iwai
   4 *
   5 *   This program is free software; you can redistribute it and/or modify
   6 *   it under the terms of the GNU General Public License as published by
   7 *   the Free Software Foundation; either version 2 of the License, or
   8 *   (at your option) any later version.
   9 *
  10 *   This program is distributed in the hope that it will be useful,
  11 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 *   GNU General Public License for more details.
  14 *
  15 *   You should have received a copy of the GNU General Public License
  16 *   along with this program; if not, write to the Free Software
  17 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  18 *
  19 */
  20
  21#include <linux/init.h>
  22#include <linux/slab.h>
  23#include <linux/module.h>
  24#include <linux/moduleparam.h>
  25#include <linux/hrtimer.h>
  26#include <sound/core.h>
  27#include <sound/timer.h>
  28
  29MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
  30MODULE_DESCRIPTION("ALSA hrtimer backend");
  31MODULE_LICENSE("GPL");
  32
  33MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER));
  34
  35#define NANO_SEC        1000000000UL    /* 10^9 in sec */
  36static unsigned int resolution;
  37
  38struct snd_hrtimer {
  39        struct snd_timer *timer;
  40        struct hrtimer hrt;
  41        atomic_t running;
  42};
  43
  44static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)
  45{
  46        struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt);
  47        struct snd_timer *t = stime->timer;
  48        unsigned long oruns;
  49
  50        if (!atomic_read(&stime->running))
  51                return HRTIMER_NORESTART;
  52
  53        oruns = hrtimer_forward_now(hrt, ns_to_ktime(t->sticks * resolution));
  54        snd_timer_interrupt(stime->timer, t->sticks * oruns);
  55
  56        if (!atomic_read(&stime->running))
  57                return HRTIMER_NORESTART;
  58        return HRTIMER_RESTART;
  59}
  60
  61static int snd_hrtimer_open(struct snd_timer *t)
  62{
  63        struct snd_hrtimer *stime;
  64
  65        stime = kmalloc(sizeof(*stime), GFP_KERNEL);
  66        if (!stime)
  67                return -ENOMEM;
  68        hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  69        stime->timer = t;
  70        stime->hrt.function = snd_hrtimer_callback;
  71        atomic_set(&stime->running, 0);
  72        t->private_data = stime;
  73        return 0;
  74}
  75
  76static int snd_hrtimer_close(struct snd_timer *t)
  77{
  78        struct snd_hrtimer *stime = t->private_data;
  79
  80        if (stime) {
  81                hrtimer_cancel(&stime->hrt);
  82                kfree(stime);
  83                t->private_data = NULL;
  84        }
  85        return 0;
  86}
  87
  88static int snd_hrtimer_start(struct snd_timer *t)
  89{
  90        struct snd_hrtimer *stime = t->private_data;
  91
  92        atomic_set(&stime->running, 0);
  93        hrtimer_cancel(&stime->hrt);
  94        hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution),
  95                      HRTIMER_MODE_REL);
  96        atomic_set(&stime->running, 1);
  97        return 0;
  98}
  99
 100static int snd_hrtimer_stop(struct snd_timer *t)
 101{
 102        struct snd_hrtimer *stime = t->private_data;
 103        atomic_set(&stime->running, 0);
 104        return 0;
 105}
 106
 107static struct snd_timer_hardware hrtimer_hw = {
 108        .flags =        SNDRV_TIMER_HW_AUTO | SNDRV_TIMER_HW_TASKLET,
 109        .open =         snd_hrtimer_open,
 110        .close =        snd_hrtimer_close,
 111        .start =        snd_hrtimer_start,
 112        .stop =         snd_hrtimer_stop,
 113};
 114
 115/*
 116 * entry functions
 117 */
 118
 119static struct snd_timer *mytimer;
 120
 121static int __init snd_hrtimer_init(void)
 122{
 123        struct snd_timer *timer;
 124        struct timespec tp;
 125        int err;
 126
 127        hrtimer_get_res(CLOCK_MONOTONIC, &tp);
 128        if (tp.tv_sec > 0 || !tp.tv_nsec) {
 129                snd_printk(KERN_ERR
 130                           "snd-hrtimer: Invalid resolution %u.%09u",
 131                           (unsigned)tp.tv_sec, (unsigned)tp.tv_nsec);
 132                return -EINVAL;
 133        }
 134        resolution = tp.tv_nsec;
 135
 136        /* Create a new timer and set up the fields */
 137        err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER,
 138                                   &timer);
 139        if (err < 0)
 140                return err;
 141
 142        timer->module = THIS_MODULE;
 143        strcpy(timer->name, "HR timer");
 144        timer->hw = hrtimer_hw;
 145        timer->hw.resolution = resolution;
 146        timer->hw.ticks = NANO_SEC / resolution;
 147
 148        err = snd_timer_global_register(timer);
 149        if (err < 0) {
 150                snd_timer_global_free(timer);
 151                return err;
 152        }
 153        mytimer = timer; /* remember this */
 154
 155        return 0;
 156}
 157
 158static void __exit snd_hrtimer_exit(void)
 159{
 160        if (mytimer) {
 161                snd_timer_global_free(mytimer);
 162                mytimer = NULL;
 163        }
 164}
 165
 166module_init(snd_hrtimer_init);
 167module_exit(snd_hrtimer_exit);
 168