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169 lines
3.6 KiB
169 lines
3.6 KiB
// 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 <[email protected]>"); |
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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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