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 };
  41
  42 static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)
  43 {
  44         struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt);
  45         struct snd_timer *t = stime->timer;
  46         hrtimer_forward_now(hrt, ns_to_ktime(t->sticks * resolution));
  47         snd_timer_interrupt(stime->timer, t->sticks);
  48         return HRTIMER_RESTART;
  49 }
  50
  51 static int snd_hrtimer_open(struct snd_timer *t)
  52 {
  53         struct snd_hrtimer *stime;
  54
  55         stime = kmalloc(sizeof(*stime), GFP_KERNEL);
  56         if (!stime)
  57                 return -ENOMEM;
  58         hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
  59         stime->timer = t;
  60         stime->hrt.cb_mode = HRTIMER_CB_IRQSAFE_UNLOCKED;
  61         stime->hrt.function = snd_hrtimer_callback;
  62         t->private_data = stime;
  63         return 0;
  64 }
  65
  66 static int snd_hrtimer_close(struct snd_timer *t)
  67 {
  68         struct snd_hrtimer *stime = t->private_data;
  69
  70         if (stime) {
  71                 hrtimer_cancel(&stime->hrt);
  72                 kfree(stime);
  73                 t->private_data = NULL;
  74         }
  75         return 0;
  76 }
  77
  78 static int snd_hrtimer_start(struct snd_timer *t)
  79 {
  80         struct snd_hrtimer *stime = t->private_data;
  81
  82         hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution),
  83                       HRTIMER_MODE_REL);
  84         return 0;
  85 }
  86
  87 static int snd_hrtimer_stop(struct snd_timer *t)
  88 {
  89         struct snd_hrtimer *stime = t->private_data;
  90
  91         hrtimer_cancel(&stime->hrt);
  92         return 0;
  93 }
  94
  95 static struct snd_timer_hardware hrtimer_hw = {
  96         .flags =        SNDRV_TIMER_HW_AUTO,
  97         .open =         snd_hrtimer_open,
  98         .close =        snd_hrtimer_close,
  99         .start =        snd_hrtimer_start,
 100         .stop =         snd_hrtimer_stop,
 101 };
 102
 103 /*
 104  * entry functions
 105  */
 106
 107 static struct snd_timer *mytimer;
 108
 109 static int __init snd_hrtimer_init(void)
 110 {
 111         struct snd_timer *timer;
 112         struct timespec tp;
 113         int err;
 114
 115         hrtimer_get_res(CLOCK_MONOTONIC, &tp);
 116         if (tp.tv_sec > 0 || !tp.tv_nsec) {
 117                 snd_printk(KERN_ERR
 118                            "snd-hrtimer: Invalid resolution %u.%09u",
 119                            (unsigned)tp.tv_sec, (unsigned)tp.tv_nsec);
 120                 return -EINVAL;
 121         }
 122         resolution = tp.tv_nsec;
 123
 124         /* Create a new timer and set up the fields */
 125         err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER,
 126                                    &timer);
 127         if (err < 0)
 128                 return err;
 129
 130         timer->module = THIS_MODULE;
 131         strcpy(timer->name, "HR timer");
 132         timer->hw = hrtimer_hw;
 133         timer->hw.resolution = resolution;
 134         timer->hw.ticks = NANO_SEC / resolution;
 135
 136         err = snd_timer_global_register(timer);
 137         if (err < 0) {
 138                 snd_timer_global_free(timer);
 139                 return err;
 140         }
 141         mytimer = timer; /* remember this */
 142
 143         return 0;
 144 }
 145
 146 static void __exit snd_hrtimer_exit(void)
 147 {
 148         if (mytimer) {
 149                 snd_timer_global_free(mytimer);
 150                 mytimer = NULL;
 151         }
 152 }
 153
 154 module_init(snd_hrtimer_init);
 155 module_exit(snd_hrtimer_exit);