170 lines
3.6 KiB
C
170 lines
3.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* ALSA timer back-end using hrtimer
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* Copyright (C) 2008 Takashi Iwai
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*/
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/hrtimer.h>
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#include <sound/core.h>
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#include <sound/timer.h>
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MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
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MODULE_DESCRIPTION("ALSA hrtimer backend");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER));
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#define NANO_SEC 1000000000UL /* 10^9 in sec */
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static unsigned int resolution;
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struct snd_hrtimer {
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struct snd_timer *timer;
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struct hrtimer hrt;
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bool in_callback;
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};
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static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt)
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{
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struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt);
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struct snd_timer *t = stime->timer;
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ktime_t delta;
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unsigned long ticks;
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enum hrtimer_restart ret = HRTIMER_NORESTART;
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spin_lock(&t->lock);
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if (!t->running)
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goto out; /* fast path */
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stime->in_callback = true;
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ticks = t->sticks;
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spin_unlock(&t->lock);
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/* calculate the drift */
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delta = ktime_sub(hrt->base->get_time(), hrtimer_get_expires(hrt));
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if (delta > 0)
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ticks += ktime_divns(delta, ticks * resolution);
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snd_timer_interrupt(stime->timer, ticks);
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spin_lock(&t->lock);
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if (t->running) {
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hrtimer_add_expires_ns(hrt, t->sticks * resolution);
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ret = HRTIMER_RESTART;
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}
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stime->in_callback = false;
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out:
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spin_unlock(&t->lock);
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return ret;
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}
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static int snd_hrtimer_open(struct snd_timer *t)
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{
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struct snd_hrtimer *stime;
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stime = kzalloc(sizeof(*stime), GFP_KERNEL);
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if (!stime)
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return -ENOMEM;
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hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
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stime->timer = t;
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stime->hrt.function = snd_hrtimer_callback;
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t->private_data = stime;
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return 0;
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}
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static int snd_hrtimer_close(struct snd_timer *t)
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{
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struct snd_hrtimer *stime = t->private_data;
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if (stime) {
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spin_lock_irq(&t->lock);
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t->running = 0; /* just to be sure */
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stime->in_callback = 1; /* skip start/stop */
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spin_unlock_irq(&t->lock);
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hrtimer_cancel(&stime->hrt);
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kfree(stime);
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t->private_data = NULL;
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}
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return 0;
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}
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static int snd_hrtimer_start(struct snd_timer *t)
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{
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struct snd_hrtimer *stime = t->private_data;
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if (stime->in_callback)
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return 0;
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hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution),
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HRTIMER_MODE_REL);
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return 0;
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}
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static int snd_hrtimer_stop(struct snd_timer *t)
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{
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struct snd_hrtimer *stime = t->private_data;
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if (stime->in_callback)
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return 0;
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hrtimer_try_to_cancel(&stime->hrt);
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return 0;
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}
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static const struct snd_timer_hardware hrtimer_hw __initconst = {
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.flags = SNDRV_TIMER_HW_AUTO | SNDRV_TIMER_HW_WORK,
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.open = snd_hrtimer_open,
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.close = snd_hrtimer_close,
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.start = snd_hrtimer_start,
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.stop = snd_hrtimer_stop,
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};
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/*
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* entry functions
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*/
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static struct snd_timer *mytimer;
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static int __init snd_hrtimer_init(void)
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{
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struct snd_timer *timer;
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int err;
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resolution = hrtimer_resolution;
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/* Create a new timer and set up the fields */
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err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER,
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&timer);
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if (err < 0)
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return err;
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timer->module = THIS_MODULE;
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strcpy(timer->name, "HR timer");
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timer->hw = hrtimer_hw;
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timer->hw.resolution = resolution;
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timer->hw.ticks = NANO_SEC / resolution;
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timer->max_instances = 100; /* lower the limit */
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err = snd_timer_global_register(timer);
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if (err < 0) {
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snd_timer_global_free(timer);
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return err;
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}
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mytimer = timer; /* remember this */
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return 0;
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}
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static void __exit snd_hrtimer_exit(void)
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{
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if (mytimer) {
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snd_timer_global_free(mytimer);
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mytimer = NULL;
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}
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}
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module_init(snd_hrtimer_init);
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module_exit(snd_hrtimer_exit);
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