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/module.h>
  23 #include <linux/moduleparam.h>
  24 #include <linux/hrtimer.h>
  25 #include <sound/core.h>
  26 #include <sound/timer.h>
  27
  28 MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
  29 MODULE_DESCRIPTION("ALSA hrtimer backend");
  30 MODULE_LICENSE("GPL");
  31
  32 MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER));
  33
  34 #define NANO_SEC        1000000000UL    /* 10^9 in sec */
  35 static unsigned int resolution;
  36
  37 struct snd_hrtimer {
  38         struct snd_timer *timer;
  39         struct hrtimer hrt;
  40         atomic_t running;
  41 };
  42
  43 static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)
  44 {
  45         struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt);
  46         struct snd_timer *t = stime->timer;
  47
  48         if (!atomic_read(&stime->running))
  49                 return HRTIMER_NORESTART;
  50
  51         hrtimer_forward_now(hrt, ns_to_ktime(t->sticks * resolution));
  52         snd_timer_interrupt(stime->timer, t->sticks);
  53
  54         if (!atomic_read(&stime->running))
  55                 return HRTIMER_NORESTART;
  56         return HRTIMER_RESTART;
  57 }
  58
  59 static int snd_hrtimer_open(struct snd_timer *t)
  60 {
  61         struct snd_hrtimer *stime;
  62
  63         stime = kmalloc(sizeof(*stime), GFP_KERNEL);
  64         if (!stime)
  65                 return -ENOMEM;
  66         hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  67         stime->timer = t;
  68         stime->hrt.function = snd_hrtimer_callback;
  69         atomic_set(&stime->running, 0);
  70         t->private_data = stime;
  71         return 0;
  72 }
  73
  74 static int snd_hrtimer_close(struct snd_timer *t)
  75 {
  76         struct snd_hrtimer *stime = t->private_data;
  77
  78         if (stime) {
  79                 hrtimer_cancel(&stime->hrt);
  80                 kfree(stime);
  81                 t->private_data = NULL;
  82         }
  83         return 0;
  84 }
  85
  86 static int snd_hrtimer_start(struct snd_timer *t)
  87 {
  88         struct snd_hrtimer *stime = t->private_data;
  89
  90         atomic_set(&stime->running, 0);
  91         hrtimer_cancel(&stime->hrt);
  92         hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution),
  93                       HRTIMER_MODE_REL);
  94         atomic_set(&stime->running, 1);
  95         return 0;
  96 }
  97
  98 static int snd_hrtimer_stop(struct snd_timer *t)
  99 {
 100         struct snd_hrtimer *stime = t->private_data;
 101         atomic_set(&stime->running, 0);
 102         return 0;
 103 }
 104
 105 static struct snd_timer_hardware hrtimer_hw = {
 106         .flags =        SNDRV_TIMER_HW_AUTO,
 107         .open =         snd_hrtimer_open,
 108         .close =        snd_hrtimer_close,
 109         .start =        snd_hrtimer_start,
 110         .stop =         snd_hrtimer_stop,
 111 };
 112
 113 /*
 114  * entry functions
 115  */
 116
 117 static struct snd_timer *mytimer;
 118
 119 static int __init snd_hrtimer_init(void)
 120 {
 121         struct snd_timer *timer;
 122         struct timespec tp;
 123         int err;
 124
 125         hrtimer_get_res(CLOCK_MONOTONIC, &tp);
 126         if (tp.tv_sec > 0 || !tp.tv_nsec) {
 127                 snd_printk(KERN_ERR
 128                            "snd-hrtimer: Invalid resolution %u.%09u",
 129                            (unsigned)tp.tv_sec, (unsigned)tp.tv_nsec);
 130                 return -EINVAL;
 131         }
 132         resolution = tp.tv_nsec;
 133
 134         /* Create a new timer and set up the fields */
 135         err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER,
 136                                    &timer);
 137         if (err < 0)
 138                 return err;
 139
 140         timer->module = THIS_MODULE;
 141         strcpy(timer->name, "HR timer");
 142         timer->hw = hrtimer_hw;
 143         timer->hw.resolution = resolution;
 144         timer->hw.ticks = NANO_SEC / resolution;
 145
 146         err = snd_timer_global_register(timer);
 147         if (err < 0) {
 148                 snd_timer_global_free(timer);
 149                 return err;
 150         }
 151         mytimer = timer; /* remember this */
 152
 153         return 0;
 154 }
 155
 156 static void __exit snd_hrtimer_exit(void)
 157 {
 158         if (mytimer) {
 159                 snd_timer_global_free(mytimer);
 160                 mytimer = NULL;
 161         }
 162 }
 163
 164 module_init(snd_hrtimer_init);
 165 module_exit(snd_hrtimer_exit);