/* * 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 > 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);