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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 | /* * ALSA timer back-end using hrtimer * Copyright (C) 2008 Takashi Iwai * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * */ #include <linux/init.h> #include <linux/slab.h> #include <linux/module.h> #include <linux/moduleparam.h> #include <linux/hrtimer.h> #include <sound/core.h> #include <sound/timer.h> MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>"); MODULE_DESCRIPTION("ALSA hrtimer backend"); MODULE_LICENSE("GPL"); MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER)); #define NANO_SEC 1000000000UL /* 10^9 in sec */ static unsigned int resolution; struct snd_hrtimer { struct snd_timer *timer; struct hrtimer hrt; bool in_callback; }; static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt) { struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt); struct snd_timer *t = stime->timer; ktime_t delta; unsigned long ticks; enum hrtimer_restart ret = HRTIMER_NORESTART; spin_lock(&t->lock); if (!t->running) goto out; /* fast path */ stime->in_callback = true; ticks = t->sticks; spin_unlock(&t->lock); /* calculate the drift */ delta = ktime_sub(hrt->base->get_time(), hrtimer_get_expires(hrt)); if (delta.tv64 > 0) ticks += ktime_divns(delta, ticks * resolution); snd_timer_interrupt(stime->timer, ticks); spin_lock(&t->lock); if (t->running) { hrtimer_add_expires_ns(hrt, t->sticks * resolution); ret = HRTIMER_RESTART; } stime->in_callback = false; out: spin_unlock(&t->lock); return ret; } static int snd_hrtimer_open(struct snd_timer *t) { struct snd_hrtimer *stime; stime = kzalloc(sizeof(*stime), GFP_KERNEL); if (!stime) return -ENOMEM; hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL); stime->timer = t; stime->hrt.function = snd_hrtimer_callback; t->private_data = stime; return 0; } static int snd_hrtimer_close(struct snd_timer *t) { struct snd_hrtimer *stime = t->private_data; if (stime) { spin_lock_irq(&t->lock); t->running = 0; /* just to be sure */ stime->in_callback = 1; /* skip start/stop */ spin_unlock_irq(&t->lock); hrtimer_cancel(&stime->hrt); kfree(stime); t->private_data = NULL; } return 0; } static int snd_hrtimer_start(struct snd_timer *t) { struct snd_hrtimer *stime = t->private_data; if (stime->in_callback) return 0; hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution), HRTIMER_MODE_REL); return 0; } static int snd_hrtimer_stop(struct snd_timer *t) { struct snd_hrtimer *stime = t->private_data; if (stime->in_callback) return 0; hrtimer_try_to_cancel(&stime->hrt); return 0; } static struct snd_timer_hardware hrtimer_hw = { .flags = SNDRV_TIMER_HW_AUTO | SNDRV_TIMER_HW_TASKLET, .open = snd_hrtimer_open, .close = snd_hrtimer_close, .start = snd_hrtimer_start, .stop = snd_hrtimer_stop, }; /* * entry functions */ static struct snd_timer *mytimer; static int __init snd_hrtimer_init(void) { struct snd_timer *timer; int err; resolution = hrtimer_resolution; /* Create a new timer and set up the fields */ err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER, &timer); if (err < 0) return err; timer->module = THIS_MODULE; strcpy(timer->name, "HR timer"); timer->hw = hrtimer_hw; timer->hw.resolution = resolution; timer->hw.ticks = NANO_SEC / resolution; err = snd_timer_global_register(timer); if (err < 0) { snd_timer_global_free(timer); return err; } mytimer = timer; /* remember this */ return 0; } static void __exit snd_hrtimer_exit(void) { if (mytimer) { snd_timer_global_free(mytimer); mytimer = NULL; } } module_init(snd_hrtimer_init); module_exit(snd_hrtimer_exit); |