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/module.h> 23 #include <linux/moduleparam.h> 24 #include <linux/hrtimer.h> 25 #include <sound/core.h> 26 #include <sound/timer.h> 27 28 MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>"); 29 MODULE_DESCRIPTION("ALSA hrtimer backend"); 30 MODULE_LICENSE("GPL"); 31 32 MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER)); 33 34 #define NANO_SEC 1000000000UL /* 10^9 in sec */ 35 static unsigned int resolution; 36 37 struct snd_hrtimer { 38 struct snd_timer *timer; 39 struct hrtimer hrt; 40 atomic_t running; 41 }; 42 43 static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt) 44 { 45 struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt); 46 struct snd_timer *t = stime->timer; 47 48 if (!atomic_read(&stime->running)) 49 return HRTIMER_NORESTART; 50 51 hrtimer_forward_now(hrt, ns_to_ktime(t->sticks * resolution)); 52 snd_timer_interrupt(stime->timer, t->sticks); 53 54 if (!atomic_read(&stime->running)) 55 return HRTIMER_NORESTART; 56 return HRTIMER_RESTART; 57 } 58 59 static int snd_hrtimer_open(struct snd_timer *t) 60 { 61 struct snd_hrtimer *stime; 62 63 stime = kmalloc(sizeof(*stime), GFP_KERNEL); 64 if (!stime) 65 return -ENOMEM; 66 hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 67 stime->timer = t; 68 stime->hrt.function = snd_hrtimer_callback; 69 atomic_set(&stime->running, 0); 70 t->private_data = stime; 71 return 0; 72 } 73 74 static int snd_hrtimer_close(struct snd_timer *t) 75 { 76 struct snd_hrtimer *stime = t->private_data; 77 78 if (stime) { 79 hrtimer_cancel(&stime->hrt); 80 kfree(stime); 81 t->private_data = NULL; 82 } 83 return 0; 84 } 85 86 static int snd_hrtimer_start(struct snd_timer *t) 87 { 88 struct snd_hrtimer *stime = t->private_data; 89 90 atomic_set(&stime->running, 0); 91 hrtimer_cancel(&stime->hrt); 92 hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution), 93 HRTIMER_MODE_REL); 94 atomic_set(&stime->running, 1); 95 return 0; 96 } 97 98 static int snd_hrtimer_stop(struct snd_timer *t) 99 { 100 struct snd_hrtimer *stime = t->private_data; 101 atomic_set(&stime->running, 0); 102 return 0; 103 } 104 105 static struct snd_timer_hardware hrtimer_hw = { 106 .flags = SNDRV_TIMER_HW_AUTO, 107 .open = snd_hrtimer_open, 108 .close = snd_hrtimer_close, 109 .start = snd_hrtimer_start, 110 .stop = snd_hrtimer_stop, 111 }; 112 113 /* 114 * entry functions 115 */ 116 117 static struct snd_timer *mytimer; 118 119 static int __init snd_hrtimer_init(void) 120 { 121 struct snd_timer *timer; 122 struct timespec tp; 123 int err; 124 125 hrtimer_get_res(CLOCK_MONOTONIC, &tp); 126 if (tp.tv_sec > 0 || !tp.tv_nsec) { 127 snd_printk(KERN_ERR 128 "snd-hrtimer: Invalid resolution %u.%09u", 129 (unsigned)tp.tv_sec, (unsigned)tp.tv_nsec); 130 return -EINVAL; 131 } 132 resolution = tp.tv_nsec; 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; 145 146 err = snd_timer_global_register(timer); 147 if (err < 0) { 148 snd_timer_global_free(timer); 149 return err; 150 } 151 mytimer = timer; /* remember this */ 152 153 return 0; 154 } 155 156 static void __exit snd_hrtimer_exit(void) 157 { 158 if (mytimer) { 159 snd_timer_global_free(mytimer); 160 mytimer = NULL; 161 } 162 } 163 164 module_init(snd_hrtimer_init); 165 module_exit(snd_hrtimer_exit); 166