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 49 if (!atomic_read(&stime->running)) 50 return HRTIMER_NORESTART; 51 52 hrtimer_forward_now(hrt, ns_to_ktime(t->sticks * resolution)); 53 snd_timer_interrupt(stime->timer, t->sticks); 54 55 if (!atomic_read(&stime->running)) 56 return HRTIMER_NORESTART; 57 return HRTIMER_RESTART; 58 } 59 60 static int snd_hrtimer_open(struct snd_timer *t) 61 { 62 struct snd_hrtimer *stime; 63 64 stime = kmalloc(sizeof(*stime), GFP_KERNEL); 65 if (!stime) 66 return -ENOMEM; 67 hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL); 68 stime->timer = t; 69 stime->hrt.function = snd_hrtimer_callback; 70 atomic_set(&stime->running, 0); 71 t->private_data = stime; 72 return 0; 73 } 74 75 static int snd_hrtimer_close(struct snd_timer *t) 76 { 77 struct snd_hrtimer *stime = t->private_data; 78 79 if (stime) { 80 hrtimer_cancel(&stime->hrt); 81 kfree(stime); 82 t->private_data = NULL; 83 } 84 return 0; 85 } 86 87 static int snd_hrtimer_start(struct snd_timer *t) 88 { 89 struct snd_hrtimer *stime = t->private_data; 90 91 atomic_set(&stime->running, 0); 92 hrtimer_cancel(&stime->hrt); 93 hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution), 94 HRTIMER_MODE_REL); 95 atomic_set(&stime->running, 1); 96 return 0; 97 } 98 99 static int snd_hrtimer_stop(struct snd_timer *t) 100 { 101 struct snd_hrtimer *stime = t->private_data; 102 atomic_set(&stime->running, 0); 103 return 0; 104 } 105 106 static struct snd_timer_hardware hrtimer_hw = { 107 .flags = SNDRV_TIMER_HW_AUTO, 108 .open = snd_hrtimer_open, 109 .close = snd_hrtimer_close, 110 .start = snd_hrtimer_start, 111 .stop = snd_hrtimer_stop, 112 }; 113 114 /* 115 * entry functions 116 */ 117 118 static struct snd_timer *mytimer; 119 120 static int __init snd_hrtimer_init(void) 121 { 122 struct snd_timer *timer; 123 struct timespec tp; 124 int err; 125 126 hrtimer_get_res(CLOCK_MONOTONIC, &tp); 127 if (tp.tv_sec > 0 || !tp.tv_nsec) { 128 snd_printk(KERN_ERR 129 "snd-hrtimer: Invalid resolution %u.%09u", 130 (unsigned)tp.tv_sec, (unsigned)tp.tv_nsec); 131 return -EINVAL; 132 } 133 resolution = tp.tv_nsec; 134 135 /* Create a new timer and set up the fields */ 136 err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER, 137 &timer); 138 if (err < 0) 139 return err; 140 141 timer->module = THIS_MODULE; 142 strcpy(timer->name, "HR timer"); 143 timer->hw = hrtimer_hw; 144 timer->hw.resolution = resolution; 145 timer->hw.ticks = NANO_SEC / resolution; 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 } 156 157 static void __exit snd_hrtimer_exit(void) 158 { 159 if (mytimer) { 160 snd_timer_global_free(mytimer); 161 mytimer = NULL; 162 } 163 } 164 165 module_init(snd_hrtimer_init); 166 module_exit(snd_hrtimer_exit); 167