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1a59d1b8 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
bbaf5e97 | 2 | /* |
647808a6 TI |
3 | * ALSA timer back-end using hrtimer |
4 | * Copyright (C) 2008 Takashi Iwai | |
bbaf5e97 TI |
5 | */ |
6 | ||
7 | #include <linux/init.h> | |
5a0e3ad6 | 8 | #include <linux/slab.h> |
bbaf5e97 TI |
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 | ||
15 | MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>"); | |
16 | MODULE_DESCRIPTION("ALSA hrtimer backend"); | |
17 | MODULE_LICENSE("GPL"); | |
18 | ||
19 | MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER)); | |
20 | ||
21 | #define NANO_SEC 1000000000UL /* 10^9 in sec */ | |
22 | static unsigned int resolution; | |
23 | ||
24 | struct snd_hrtimer { | |
25 | struct snd_timer *timer; | |
26 | struct hrtimer hrt; | |
d2c5cf88 | 27 | bool in_callback; |
bbaf5e97 TI |
28 | }; |
29 | ||
30 | static 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; | |
d2c5cf88 TI |
34 | ktime_t delta; |
35 | unsigned long ticks; | |
36 | enum hrtimer_restart ret = HRTIMER_NORESTART; | |
37 | ||
38 | spin_lock(&t->lock); | |
39 | if (!t->running) | |
40 | goto out; /* fast path */ | |
41 | stime->in_callback = true; | |
42 | ticks = t->sticks; | |
43 | spin_unlock(&t->lock); | |
44 | ||
45 | /* calculate the drift */ | |
46 | delta = ktime_sub(hrt->base->get_time(), hrtimer_get_expires(hrt)); | |
2456e855 | 47 | if (delta > 0) |
d2c5cf88 TI |
48 | ticks += ktime_divns(delta, ticks * resolution); |
49 | ||
50 | snd_timer_interrupt(stime->timer, ticks); | |
51 | ||
52 | spin_lock(&t->lock); | |
53 | if (t->running) { | |
54 | hrtimer_add_expires_ns(hrt, t->sticks * resolution); | |
55 | ret = HRTIMER_RESTART; | |
56 | } | |
fcfdebe7 | 57 | |
d2c5cf88 TI |
58 | stime->in_callback = false; |
59 | out: | |
60 | spin_unlock(&t->lock); | |
61 | return ret; | |
bbaf5e97 TI |
62 | } |
63 | ||
64 | static int snd_hrtimer_open(struct snd_timer *t) | |
65 | { | |
66 | struct snd_hrtimer *stime; | |
67 | ||
d2c5cf88 | 68 | stime = kzalloc(sizeof(*stime), GFP_KERNEL); |
bbaf5e97 TI |
69 | if (!stime) |
70 | return -ENOMEM; | |
71 | hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL); | |
72 | stime->timer = t; | |
bbaf5e97 TI |
73 | stime->hrt.function = snd_hrtimer_callback; |
74 | t->private_data = stime; | |
75 | return 0; | |
76 | } | |
77 | ||
78 | static int snd_hrtimer_close(struct snd_timer *t) | |
79 | { | |
80 | struct snd_hrtimer *stime = t->private_data; | |
81 | ||
82 | if (stime) { | |
d2c5cf88 TI |
83 | spin_lock_irq(&t->lock); |
84 | t->running = 0; /* just to be sure */ | |
85 | stime->in_callback = 1; /* skip start/stop */ | |
86 | spin_unlock_irq(&t->lock); | |
87 | ||
bbaf5e97 TI |
88 | hrtimer_cancel(&stime->hrt); |
89 | kfree(stime); | |
90 | t->private_data = NULL; | |
91 | } | |
92 | return 0; | |
93 | } | |
94 | ||
95 | static int snd_hrtimer_start(struct snd_timer *t) | |
96 | { | |
97 | struct snd_hrtimer *stime = t->private_data; | |
98 | ||
d2c5cf88 TI |
99 | if (stime->in_callback) |
100 | return 0; | |
647808a6 | 101 | hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution), |
bbaf5e97 TI |
102 | HRTIMER_MODE_REL); |
103 | return 0; | |
104 | } | |
105 | ||
106 | static int snd_hrtimer_stop(struct snd_timer *t) | |
107 | { | |
108 | struct snd_hrtimer *stime = t->private_data; | |
d2c5cf88 TI |
109 | |
110 | if (stime->in_callback) | |
111 | return 0; | |
2ba1fe7a | 112 | hrtimer_try_to_cancel(&stime->hrt); |
bbaf5e97 TI |
113 | return 0; |
114 | } | |
115 | ||
38405834 | 116 | static const struct snd_timer_hardware hrtimer_hw __initconst = { |
2243c4d0 | 117 | .flags = SNDRV_TIMER_HW_AUTO | SNDRV_TIMER_HW_TASKLET, |
bbaf5e97 TI |
118 | .open = snd_hrtimer_open, |
119 | .close = snd_hrtimer_close, | |
120 | .start = snd_hrtimer_start, | |
121 | .stop = snd_hrtimer_stop, | |
122 | }; | |
123 | ||
124 | /* | |
125 | * entry functions | |
126 | */ | |
127 | ||
128 | static struct snd_timer *mytimer; | |
129 | ||
130 | static int __init snd_hrtimer_init(void) | |
131 | { | |
132 | struct snd_timer *timer; | |
bbaf5e97 TI |
133 | int err; |
134 | ||
447fbbdc | 135 | resolution = hrtimer_resolution; |
bbaf5e97 TI |
136 | |
137 | /* Create a new timer and set up the fields */ | |
138 | err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER, | |
139 | &timer); | |
140 | if (err < 0) | |
141 | return err; | |
142 | ||
143 | timer->module = THIS_MODULE; | |
144 | strcpy(timer->name, "HR timer"); | |
145 | timer->hw = hrtimer_hw; | |
146 | timer->hw.resolution = resolution; | |
147 | timer->hw.ticks = NANO_SEC / resolution; | |
9b7d869e | 148 | timer->max_instances = 100; /* lower the limit */ |
bbaf5e97 TI |
149 | |
150 | err = snd_timer_global_register(timer); | |
151 | if (err < 0) { | |
152 | snd_timer_global_free(timer); | |
153 | return err; | |
154 | } | |
155 | mytimer = timer; /* remember this */ | |
156 | ||
157 | return 0; | |
158 | } | |
159 | ||
160 | static void __exit snd_hrtimer_exit(void) | |
161 | { | |
162 | if (mytimer) { | |
163 | snd_timer_global_free(mytimer); | |
164 | mytimer = NULL; | |
165 | } | |
166 | } | |
167 | ||
168 | module_init(snd_hrtimer_init); | |
169 | module_exit(snd_hrtimer_exit); |