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bbaf5e97 | 1 | /* |
647808a6 TI |
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 | * | |
bbaf5e97 TI |
19 | */ |
20 | ||
21 | #include <linux/init.h> | |
5a0e3ad6 | 22 | #include <linux/slab.h> |
bbaf5e97 TI |
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; | |
d2c5cf88 | 41 | bool in_callback; |
bbaf5e97 TI |
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; | |
d2c5cf88 TI |
48 | ktime_t delta; |
49 | unsigned long ticks; | |
50 | enum hrtimer_restart ret = HRTIMER_NORESTART; | |
51 | ||
52 | spin_lock(&t->lock); | |
53 | if (!t->running) | |
54 | goto out; /* fast path */ | |
55 | stime->in_callback = true; | |
56 | ticks = t->sticks; | |
57 | spin_unlock(&t->lock); | |
58 | ||
59 | /* calculate the drift */ | |
60 | delta = ktime_sub(hrt->base->get_time(), hrtimer_get_expires(hrt)); | |
61 | if (delta.tv64 > 0) | |
62 | ticks += ktime_divns(delta, ticks * resolution); | |
63 | ||
64 | snd_timer_interrupt(stime->timer, ticks); | |
65 | ||
66 | spin_lock(&t->lock); | |
67 | if (t->running) { | |
68 | hrtimer_add_expires_ns(hrt, t->sticks * resolution); | |
69 | ret = HRTIMER_RESTART; | |
70 | } | |
fcfdebe7 | 71 | |
d2c5cf88 TI |
72 | stime->in_callback = false; |
73 | out: | |
74 | spin_unlock(&t->lock); | |
75 | return ret; | |
bbaf5e97 TI |
76 | } |
77 | ||
78 | static int snd_hrtimer_open(struct snd_timer *t) | |
79 | { | |
80 | struct snd_hrtimer *stime; | |
81 | ||
d2c5cf88 | 82 | stime = kzalloc(sizeof(*stime), GFP_KERNEL); |
bbaf5e97 TI |
83 | if (!stime) |
84 | return -ENOMEM; | |
85 | hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
86 | stime->timer = t; | |
bbaf5e97 TI |
87 | stime->hrt.function = snd_hrtimer_callback; |
88 | t->private_data = stime; | |
89 | return 0; | |
90 | } | |
91 | ||
92 | static int snd_hrtimer_close(struct snd_timer *t) | |
93 | { | |
94 | struct snd_hrtimer *stime = t->private_data; | |
95 | ||
96 | if (stime) { | |
d2c5cf88 TI |
97 | spin_lock_irq(&t->lock); |
98 | t->running = 0; /* just to be sure */ | |
99 | stime->in_callback = 1; /* skip start/stop */ | |
100 | spin_unlock_irq(&t->lock); | |
101 | ||
bbaf5e97 TI |
102 | hrtimer_cancel(&stime->hrt); |
103 | kfree(stime); | |
104 | t->private_data = NULL; | |
105 | } | |
106 | return 0; | |
107 | } | |
108 | ||
109 | static int snd_hrtimer_start(struct snd_timer *t) | |
110 | { | |
111 | struct snd_hrtimer *stime = t->private_data; | |
112 | ||
d2c5cf88 TI |
113 | if (stime->in_callback) |
114 | return 0; | |
647808a6 | 115 | hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution), |
bbaf5e97 TI |
116 | HRTIMER_MODE_REL); |
117 | return 0; | |
118 | } | |
119 | ||
120 | static int snd_hrtimer_stop(struct snd_timer *t) | |
121 | { | |
122 | struct snd_hrtimer *stime = t->private_data; | |
d2c5cf88 TI |
123 | |
124 | if (stime->in_callback) | |
125 | return 0; | |
2ba1fe7a | 126 | hrtimer_try_to_cancel(&stime->hrt); |
bbaf5e97 TI |
127 | return 0; |
128 | } | |
129 | ||
130 | static struct snd_timer_hardware hrtimer_hw = { | |
2243c4d0 | 131 | .flags = SNDRV_TIMER_HW_AUTO | SNDRV_TIMER_HW_TASKLET, |
bbaf5e97 TI |
132 | .open = snd_hrtimer_open, |
133 | .close = snd_hrtimer_close, | |
134 | .start = snd_hrtimer_start, | |
135 | .stop = snd_hrtimer_stop, | |
136 | }; | |
137 | ||
138 | /* | |
139 | * entry functions | |
140 | */ | |
141 | ||
142 | static struct snd_timer *mytimer; | |
143 | ||
144 | static int __init snd_hrtimer_init(void) | |
145 | { | |
146 | struct snd_timer *timer; | |
bbaf5e97 TI |
147 | int err; |
148 | ||
447fbbdc | 149 | resolution = hrtimer_resolution; |
bbaf5e97 TI |
150 | |
151 | /* Create a new timer and set up the fields */ | |
152 | err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER, | |
153 | &timer); | |
154 | if (err < 0) | |
155 | return err; | |
156 | ||
157 | timer->module = THIS_MODULE; | |
158 | strcpy(timer->name, "HR timer"); | |
159 | timer->hw = hrtimer_hw; | |
160 | timer->hw.resolution = resolution; | |
161 | timer->hw.ticks = NANO_SEC / resolution; | |
162 | ||
163 | err = snd_timer_global_register(timer); | |
164 | if (err < 0) { | |
165 | snd_timer_global_free(timer); | |
166 | return err; | |
167 | } | |
168 | mytimer = timer; /* remember this */ | |
169 | ||
170 | return 0; | |
171 | } | |
172 | ||
173 | static void __exit snd_hrtimer_exit(void) | |
174 | { | |
175 | if (mytimer) { | |
176 | snd_timer_global_free(mytimer); | |
177 | mytimer = NULL; | |
178 | } | |
179 | } | |
180 | ||
181 | module_init(snd_hrtimer_init); | |
182 | module_exit(snd_hrtimer_exit); |