2 * ALSA timer back-end using hrtimer
3 * Copyright (C) 2008 Takashi Iwai
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.
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.
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
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>
28 MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
29 MODULE_DESCRIPTION("ALSA hrtimer backend");
30 MODULE_LICENSE("GPL");
32 MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER));
34 #define NANO_SEC 1000000000UL /* 10^9 in sec */
35 static unsigned int resolution;
38 struct snd_timer *timer;
43 static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)
45 struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt);
46 struct snd_timer *t = stime->timer;
48 if (!atomic_read(&stime->running))
49 return HRTIMER_NORESTART;
51 hrtimer_forward_now(hrt, ns_to_ktime(t->sticks * resolution));
52 snd_timer_interrupt(stime->timer, t->sticks);
54 if (!atomic_read(&stime->running))
55 return HRTIMER_NORESTART;
56 return HRTIMER_RESTART;
59 static int snd_hrtimer_open(struct snd_timer *t)
61 struct snd_hrtimer *stime;
63 stime = kmalloc(sizeof(*stime), GFP_KERNEL);
66 hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
68 stime->hrt.function = snd_hrtimer_callback;
69 atomic_set(&stime->running, 0);
70 t->private_data = stime;
74 static int snd_hrtimer_close(struct snd_timer *t)
76 struct snd_hrtimer *stime = t->private_data;
79 hrtimer_cancel(&stime->hrt);
81 t->private_data = NULL;
86 static int snd_hrtimer_start(struct snd_timer *t)
88 struct snd_hrtimer *stime = t->private_data;
90 atomic_set(&stime->running, 0);
91 hrtimer_cancel(&stime->hrt);
92 hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution),
94 atomic_set(&stime->running, 1);
98 static int snd_hrtimer_stop(struct snd_timer *t)
100 struct snd_hrtimer *stime = t->private_data;
101 atomic_set(&stime->running, 0);
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,
117 static struct snd_timer *mytimer;
119 static int __init snd_hrtimer_init(void)
121 struct snd_timer *timer;
125 hrtimer_get_res(CLOCK_MONOTONIC, &tp);
126 if (tp.tv_sec > 0 || !tp.tv_nsec) {
128 "snd-hrtimer: Invalid resolution %u.%09u",
129 (unsigned)tp.tv_sec, (unsigned)tp.tv_nsec);
132 resolution = tp.tv_nsec;
134 /* Create a new timer and set up the fields */
135 err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER,
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;
146 err = snd_timer_global_register(timer);
148 snd_timer_global_free(timer);
151 mytimer = timer; /* remember this */
156 static void __exit snd_hrtimer_exit(void)
159 snd_timer_global_free(mytimer);
164 module_init(snd_hrtimer_init);
165 module_exit(snd_hrtimer_exit);