Linux kernel mirror (for testing)
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linux
1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * ALSA timer back-end using hrtimer
4 * Copyright (C) 2008 Takashi Iwai
5 */
6
7#include <linux/init.h>
8#include <linux/slab.h>
9#include <linux/module.h>
10#include <linux/moduleparam.h>
11#include <linux/hrtimer.h>
12#include <sound/core.h>
13#include <sound/timer.h>
14
15MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
16MODULE_DESCRIPTION("ALSA hrtimer backend");
17MODULE_LICENSE("GPL");
18
19MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER));
20
21#define NANO_SEC 1000000000UL /* 10^9 in sec */
22static unsigned int resolution;
23
24struct snd_hrtimer {
25 struct snd_timer *timer;
26 struct hrtimer hrt;
27 bool in_callback;
28};
29
30static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)
31{
32 struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt);
33 struct snd_timer *t = stime->timer;
34 ktime_t delta;
35 unsigned long ticks;
36 enum hrtimer_restart ret = HRTIMER_NORESTART;
37
38 scoped_guard(spinlock, &t->lock) {
39 if (!t->running)
40 return HRTIMER_NORESTART; /* fast path */
41 stime->in_callback = true;
42 ticks = t->sticks;
43 }
44
45 /* calculate the drift */
46 delta = ktime_sub(hrt->base->get_time(), hrtimer_get_expires(hrt));
47 if (delta > 0)
48 ticks += ktime_divns(delta, ticks * resolution);
49
50 snd_timer_interrupt(stime->timer, ticks);
51
52 guard(spinlock)(&t->lock);
53 if (t->running) {
54 hrtimer_add_expires_ns(hrt, t->sticks * resolution);
55 ret = HRTIMER_RESTART;
56 }
57
58 stime->in_callback = false;
59 return ret;
60}
61
62static int snd_hrtimer_open(struct snd_timer *t)
63{
64 struct snd_hrtimer *stime;
65
66 stime = kzalloc(sizeof(*stime), GFP_KERNEL);
67 if (!stime)
68 return -ENOMEM;
69 stime->timer = t;
70 hrtimer_setup(&stime->hrt, snd_hrtimer_callback, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
71 t->private_data = stime;
72 return 0;
73}
74
75static int snd_hrtimer_close(struct snd_timer *t)
76{
77 struct snd_hrtimer *stime = t->private_data;
78
79 if (stime) {
80 scoped_guard(spinlock_irq, &t->lock) {
81 t->running = 0; /* just to be sure */
82 stime->in_callback = 1; /* skip start/stop */
83 }
84
85 hrtimer_cancel(&stime->hrt);
86 kfree(stime);
87 t->private_data = NULL;
88 }
89 return 0;
90}
91
92static int snd_hrtimer_start(struct snd_timer *t)
93{
94 struct snd_hrtimer *stime = t->private_data;
95
96 if (stime->in_callback)
97 return 0;
98 hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution),
99 HRTIMER_MODE_REL);
100 return 0;
101}
102
103static int snd_hrtimer_stop(struct snd_timer *t)
104{
105 struct snd_hrtimer *stime = t->private_data;
106
107 if (stime->in_callback)
108 return 0;
109 hrtimer_try_to_cancel(&stime->hrt);
110 return 0;
111}
112
113static const struct snd_timer_hardware hrtimer_hw __initconst = {
114 .flags = SNDRV_TIMER_HW_AUTO | SNDRV_TIMER_HW_WORK,
115 .open = snd_hrtimer_open,
116 .close = snd_hrtimer_close,
117 .start = snd_hrtimer_start,
118 .stop = snd_hrtimer_stop,
119};
120
121/*
122 * entry functions
123 */
124
125static struct snd_timer *mytimer;
126
127static int __init snd_hrtimer_init(void)
128{
129 struct snd_timer *timer;
130 int err;
131
132 resolution = hrtimer_resolution;
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 timer->max_instances = 100; /* lower the limit */
146
147 err = snd_timer_global_register(timer);
148 if (err < 0) {
149 snd_timer_global_free(timer);
150 return err;
151 }
152 mytimer = timer; /* remember this */
153
154 return 0;
155}
156
157static void __exit snd_hrtimer_exit(void)
158{
159 if (mytimer) {
160 snd_timer_global_free(mytimer);
161 mytimer = NULL;
162 }
163}
164
165module_init(snd_hrtimer_init);
166module_exit(snd_hrtimer_exit);