linux/sound/core/hrtimer.c
Takashi Iwai bf0835957f ALSA: timer: Replace tasklet with work
The tasklet is an old API that should be deprecated, usually can be
converted to another decent API.  In ALSA core timer API, the
callbacks can be offlined to a tasklet when a flag is set in the timer
backend.  It can be achieved gracefully with a work queued in the
high-prio system workqueue.

This patch replaces the usage of tasklet in ALSA timer API with a
simple work.  Currently the tasklet feature is used only in the system
timer and hrtimer backends, so both are patched to use the new flag
name SNDRV_TIMER_HW_WORK, too.

Link: https://lore.kernel.org/r/20200903104131.21097-3-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2020-09-09 18:32:52 +02:00

170 lines
3.6 KiB
C

// 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);