mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-22 17:01:14 +00:00
![Takashi Iwai](/assets/img/avatar_default.png)
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>
169 lines
3.6 KiB
C
169 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);
|