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_try_to_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	hrtimer_try_to_cancel(&stime->hrt);
105	return 0;
106}
107
108static struct snd_timer_hardware hrtimer_hw = {
109	.flags =	SNDRV_TIMER_HW_AUTO | SNDRV_TIMER_HW_TASKLET,
110	.open =		snd_hrtimer_open,
111	.close =	snd_hrtimer_close,
112	.start =	snd_hrtimer_start,
113	.stop =		snd_hrtimer_stop,
114};
115
116/*
117 * entry functions
118 */
119
120static struct snd_timer *mytimer;
121
122static int __init snd_hrtimer_init(void)
123{
124	struct snd_timer *timer;
125	struct timespec tp;
126	int err;
127
128	hrtimer_get_res(CLOCK_MONOTONIC, &tp);
129	if (tp.tv_sec > 0 || !tp.tv_nsec) {
130		pr_err("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