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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* ALSA timer back-end using hrtimer
* Copyright (C) 2008 Takashi Iwai
*/
#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 > 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 const struct snd_timer_hardware hrtimer_hw __initconst = {
.flags = SNDRV_TIMER_HW_AUTO | SNDRV_TIMER_HW_WORK,
.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;
timer->max_instances = 100; /* lower the limit */
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);
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