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/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>
29 MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
30 MODULE_DESCRIPTION("ALSA hrtimer backend");
31 MODULE_LICENSE("GPL");
33 MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER
));
35 #define NANO_SEC 1000000000UL /* 10^9 in sec */
36 static unsigned int resolution
;
39 struct snd_timer
*timer
;
44 static enum hrtimer_restart
snd_hrtimer_callback(struct hrtimer
*hrt
)
46 struct snd_hrtimer
*stime
= container_of(hrt
, struct snd_hrtimer
, hrt
);
47 struct snd_timer
*t
= stime
->timer
;
50 if (!atomic_read(&stime
->running
))
51 return HRTIMER_NORESTART
;
53 oruns
= hrtimer_forward_now(hrt
, ns_to_ktime(t
->sticks
* resolution
));
54 snd_timer_interrupt(stime
->timer
, t
->sticks
* oruns
);
56 if (!atomic_read(&stime
->running
))
57 return HRTIMER_NORESTART
;
58 return HRTIMER_RESTART
;
61 static int snd_hrtimer_open(struct snd_timer
*t
)
63 struct snd_hrtimer
*stime
;
65 stime
= kmalloc(sizeof(*stime
), GFP_KERNEL
);
68 hrtimer_init(&stime
->hrt
, CLOCK_MONOTONIC
, HRTIMER_MODE_REL
);
70 stime
->hrt
.function
= snd_hrtimer_callback
;
71 atomic_set(&stime
->running
, 0);
72 t
->private_data
= stime
;
76 static int snd_hrtimer_close(struct snd_timer
*t
)
78 struct snd_hrtimer
*stime
= t
->private_data
;
81 hrtimer_cancel(&stime
->hrt
);
83 t
->private_data
= NULL
;
88 static int snd_hrtimer_start(struct snd_timer
*t
)
90 struct snd_hrtimer
*stime
= t
->private_data
;
92 atomic_set(&stime
->running
, 0);
93 hrtimer_try_to_cancel(&stime
->hrt
);
94 hrtimer_start(&stime
->hrt
, ns_to_ktime(t
->sticks
* resolution
),
96 atomic_set(&stime
->running
, 1);
100 static int snd_hrtimer_stop(struct snd_timer
*t
)
102 struct snd_hrtimer
*stime
= t
->private_data
;
103 atomic_set(&stime
->running
, 0);
104 hrtimer_try_to_cancel(&stime
->hrt
);
108 static 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
,
120 static struct snd_timer
*mytimer
;
122 static int __init
snd_hrtimer_init(void)
124 struct snd_timer
*timer
;
128 hrtimer_get_res(CLOCK_MONOTONIC
, &tp
);
129 if (tp
.tv_sec
> 0 || !tp
.tv_nsec
) {
131 "snd-hrtimer: Invalid resolution %u.%09u",
132 (unsigned)tp
.tv_sec
, (unsigned)tp
.tv_nsec
);
135 resolution
= tp
.tv_nsec
;
137 /* Create a new timer and set up the fields */
138 err
= snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER
,
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
;
149 err
= snd_timer_global_register(timer
);
151 snd_timer_global_free(timer
);
154 mytimer
= timer
; /* remember this */
159 static void __exit
snd_hrtimer_exit(void)
162 snd_timer_global_free(mytimer
);
167 module_init(snd_hrtimer_init
);
168 module_exit(snd_hrtimer_exit
);