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
  29 MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
  30 MODULE_DESCRIPTION("ALSA hrtimer backend");
  31 MODULE_LICENSE("GPL");
  32
  33 MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER));
  34
  35 #define NANO_SEC        1000000000UL    /* 10^9 in sec */
  36 static unsigned int resolution;
  37
  38 struct snd_hrtimer {
  39         struct snd_timer *timer;
  40         struct hrtimer hrt;
  41         atomic_t running;
  42 };
  43
  44 static 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
  49         if (!atomic_read(&stime->running))
  50                 return HRTIMER_NORESTART;
  51
  52         hrtimer_forward_now(hrt, ns_to_ktime(t->sticks * resolution));
  53         snd_timer_interrupt(stime->timer, t->sticks);
  54
  55         if (!atomic_read(&stime->running))
  56                 return HRTIMER_NORESTART;
  57         return HRTIMER_RESTART;
  58 }
  59
  60 static int snd_hrtimer_open(struct snd_timer *t)
  61 {
  62         struct snd_hrtimer *stime;
  63
  64         stime = kmalloc(sizeof(*stime), GFP_KERNEL);
  65         if (!stime)
  66                 return -ENOMEM;
  67         hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  68         stime->timer = t;
  69         stime->hrt.function = snd_hrtimer_callback;
  70         atomic_set(&stime->running, 0);
  71         t->private_data = stime;
  72         return 0;
  73 }
  74
  75 static int snd_hrtimer_close(struct snd_timer *t)
  76 {
  77         struct snd_hrtimer *stime = t->private_data;
  78
  79         if (stime) {
  80                 hrtimer_cancel(&stime->hrt);
  81                 kfree(stime);
  82                 t->private_data = NULL;
  83         }
  84         return 0;
  85 }
  86
  87 static int snd_hrtimer_start(struct snd_timer *t)
  88 {
  89         struct snd_hrtimer *stime = t->private_data;
  90
  91         atomic_set(&stime->running, 0);
  92         hrtimer_cancel(&stime->hrt);
  93         hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution),
  94                       HRTIMER_MODE_REL);
  95         atomic_set(&stime->running, 1);
  96         return 0;
  97 }
  98
  99 static int snd_hrtimer_stop(struct snd_timer *t)
 100 {
 101         struct snd_hrtimer *stime = t->private_data;
 102         atomic_set(&stime->running, 0);
 103         return 0;
 104 }
 105
 106 static struct snd_timer_hardware hrtimer_hw = {
 107         .flags =        SNDRV_TIMER_HW_AUTO,
 108         .open =         snd_hrtimer_open,
 109         .close =        snd_hrtimer_close,
 110         .start =        snd_hrtimer_start,
 111         .stop =         snd_hrtimer_stop,
 112 };
 113
 114 /*
 115  * entry functions
 116  */
 117
 118 static struct snd_timer *mytimer;
 119
 120 static int __init snd_hrtimer_init(void)
 121 {
 122         struct snd_timer *timer;
 123         struct timespec tp;
 124         int err;
 125
 126         hrtimer_get_res(CLOCK_MONOTONIC, &tp);
 127         if (tp.tv_sec > 0 || !tp.tv_nsec) {
 128                 snd_printk(KERN_ERR
 129                            "snd-hrtimer: Invalid resolution %u.%09u",
 130                            (unsigned)tp.tv_sec, (unsigned)tp.tv_nsec);
 131                 return -EINVAL;
 132         }
 133         resolution = tp.tv_nsec;
 134
 135         /* Create a new timer and set up the fields */
 136         err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER,
 137                                    &timer);
 138         if (err < 0)
 139                 return err;
 140
 141         timer->module = THIS_MODULE;
 142         strcpy(timer->name, "HR timer");
 143         timer->hw = hrtimer_hw;
 144         timer->hw.resolution = resolution;
 145         timer->hw.ticks = NANO_SEC / resolution;
 146
 147         err = snd_timer_global_register(timer);
 148         if (err < 0) {
 149                 snd_timer_global_free(timer);
 150                 return err;
 151         }
 152         mytimer = timer; /* remember this */
 153
 154         return 0;
 155 }
 156
 157 static void __exit snd_hrtimer_exit(void)
 158 {
 159         if (mytimer) {
 160                 snd_timer_global_free(mytimer);
 161                 mytimer = NULL;
 162         }
 163 }
 164
 165 module_init(snd_hrtimer_init);
 166 module_exit(snd_hrtimer_exit);