1/*
  2 *  RTC based high-frequency timer
  3 *
  4 *  Copyright (C) 2000 Takashi Iwai
  5 *	based on rtctimer.c by Steve Ratcliffe
  6 *
  7 *   This program is free software; you can redistribute it and/or modify
  8 *   it under the terms of the GNU General Public License as published by
  9 *   the Free Software Foundation; either version 2 of the License, or
 10 *   (at your option) any later version.
 11 *
 12 *   This program is distributed in the hope that it will be useful,
 13 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 14 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 15 *   GNU General Public License for more details.
 16 *
 17 *   You should have received a copy of the GNU General Public License
 18 *   along with this program; if not, write to the Free Software
 19 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 20 *
 21 */
 22
 23#include <linux/init.h>
 24#include <linux/interrupt.h>
 25#include <linux/module.h>
 26#include <linux/log2.h>
 27#include <sound/core.h>
 28#include <sound/timer.h>
 29
 30#if IS_ENABLED(CONFIG_RTC)
 31
 32#include <linux/mc146818rtc.h>
 33
 34#define RTC_FREQ	1024		/* default frequency */
 35#define NANO_SEC	1000000000L	/* 10^9 in sec */
 36
 37/*
 38 * prototypes
 39 */
 40static int rtctimer_open(struct snd_timer *t);
 41static int rtctimer_close(struct snd_timer *t);
 42static int rtctimer_start(struct snd_timer *t);
 43static int rtctimer_stop(struct snd_timer *t);
 44
 45
 46/*
 47 * The hardware dependent description for this timer.
 48 */
 49static struct snd_timer_hardware rtc_hw = {
 50	.flags =	SNDRV_TIMER_HW_AUTO |
 51			SNDRV_TIMER_HW_FIRST |
 52			SNDRV_TIMER_HW_TASKLET,
 53	.ticks =	100000000L,		/* FIXME: XXX */
 54	.open =		rtctimer_open,
 55	.close =	rtctimer_close,
 56	.start =	rtctimer_start,
 57	.stop =		rtctimer_stop,
 58};
 59
 60static int rtctimer_freq = RTC_FREQ;		/* frequency */
 61static struct snd_timer *rtctimer;
 62static struct tasklet_struct rtc_tasklet;
 63static rtc_task_t rtc_task;
 64
 65
 66static int
 67rtctimer_open(struct snd_timer *t)
 68{
 69	int err;
 70
 71	err = rtc_register(&rtc_task);
 72	if (err < 0)
 73		return err;
 74	t->private_data = &rtc_task;
 75	return 0;
 76}
 77
 78static int
 79rtctimer_close(struct snd_timer *t)
 80{
 81	rtc_task_t *rtc = t->private_data;
 82	if (rtc) {
 83		rtc_unregister(rtc);
 84		tasklet_kill(&rtc_tasklet);
 85		t->private_data = NULL;
 86	}
 87	return 0;
 88}
 89
 90static int
 91rtctimer_start(struct snd_timer *timer)
 92{
 93	rtc_task_t *rtc = timer->private_data;
 94	if (snd_BUG_ON(!rtc))
 95		return -EINVAL;
 96	rtc_control(rtc, RTC_IRQP_SET, rtctimer_freq);
 97	rtc_control(rtc, RTC_PIE_ON, 0);
 98	return 0;
 99}
100
101static int
102rtctimer_stop(struct snd_timer *timer)
103{
104	rtc_task_t *rtc = timer->private_data;
105	if (snd_BUG_ON(!rtc))
106		return -EINVAL;
107	rtc_control(rtc, RTC_PIE_OFF, 0);
108	return 0;
109}
110
111static void rtctimer_tasklet(unsigned long data)
112{
113	snd_timer_interrupt((struct snd_timer *)data, 1);
114}
115
116/*
117 * interrupt
118 */
119static void rtctimer_interrupt(void *private_data)
120{
121	tasklet_schedule(private_data);
122}
123
124
125/*
126 *  ENTRY functions
127 */
128static int __init rtctimer_init(void)
129{
130	int err;
131	struct snd_timer *timer;
132
133	if (rtctimer_freq < 2 || rtctimer_freq > 8192 ||
134	    !is_power_of_2(rtctimer_freq)) {
135		pr_err("ALSA: rtctimer: invalid frequency %d\n", rtctimer_freq);
136		return -EINVAL;
137	}
138
139	/* Create a new timer and set up the fields */
140	err = snd_timer_global_new("rtc", SNDRV_TIMER_GLOBAL_RTC, &timer);
141	if (err < 0)
142		return err;
143
144	timer->module = THIS_MODULE;
145	strcpy(timer->name, "RTC timer");
146	timer->hw = rtc_hw;
147	timer->hw.resolution = NANO_SEC / rtctimer_freq;
148
149	tasklet_init(&rtc_tasklet, rtctimer_tasklet, (unsigned long)timer);
150
151	/* set up RTC callback */
152	rtc_task.func = rtctimer_interrupt;
153	rtc_task.private_data = &rtc_tasklet;
154
155	err = snd_timer_global_register(timer);
156	if (err < 0) {
157		snd_timer_global_free(timer);
158		return err;
159	}
160	rtctimer = timer; /* remember this */
161
162	return 0;
163}
164
165static void __exit rtctimer_exit(void)
166{
167	if (rtctimer) {
168		snd_timer_global_free(rtctimer);
169		rtctimer = NULL;
170	}
171}
172
173
174/*
175 * exported stuff
176 */
177module_init(rtctimer_init)
178module_exit(rtctimer_exit)
179
180module_param(rtctimer_freq, int, 0444);
181MODULE_PARM_DESC(rtctimer_freq, "timer frequency in Hz");
182
183MODULE_LICENSE("GPL");
184
185MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_RTC));
186
187#endif /* IS_ENABLED(CONFIG_RTC) */