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 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; 41 atomic_t running; 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; 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 61 static 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 76 static 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 88 static 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 } 99 100 static 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 } 107 108 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, 114 }; 115 116 /* 117 * entry functions 118 */ 119 120 static struct snd_timer *mytimer; 121 122 static int __init snd_hrtimer_init(void) 123 { 124 struct snd_timer *timer; 125 int err; 126 127 resolution = hrtimer_resolution; 128 129 /* Create a new timer and set up the fields */ 130 err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER, 131 &timer); 132 if (err < 0) 133 return err; 134 135 timer->module = THIS_MODULE; 136 strcpy(timer->name, "HR timer"); 137 timer->hw = hrtimer_hw; 138 timer->hw.resolution = resolution; 139 timer->hw.ticks = NANO_SEC / resolution; 140 141 err = snd_timer_global_register(timer); 142 if (err < 0) { 143 snd_timer_global_free(timer); 144 return err; 145 } 146 mytimer = timer; /* remember this */ 147 148 return 0; 149 } 150 151 static void __exit snd_hrtimer_exit(void) 152 { 153 if (mytimer) { 154 snd_timer_global_free(mytimer); 155 mytimer = NULL; 156 } 157 } 158 159 module_init(snd_hrtimer_init); 160 module_exit(snd_hrtimer_exit); 161