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Linux/sound/core/rtctimer.c

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  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  */
 40 static int rtctimer_open(struct snd_timer *t);
 41 static int rtctimer_close(struct snd_timer *t);
 42 static int rtctimer_start(struct snd_timer *t);
 43 static int rtctimer_stop(struct snd_timer *t);
 44 
 45 
 46 /*
 47  * The hardware dependent description for this timer.
 48  */
 49 static 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 
 60 static int rtctimer_freq = RTC_FREQ;            /* frequency */
 61 static struct snd_timer *rtctimer;
 62 static struct tasklet_struct rtc_tasklet;
 63 static rtc_task_t rtc_task;
 64 
 65 
 66 static int
 67 rtctimer_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 
 78 static int
 79 rtctimer_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 
 90 static int
 91 rtctimer_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 
101 static int
102 rtctimer_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 
111 static void rtctimer_tasklet(unsigned long data)
112 {
113         snd_timer_interrupt((struct snd_timer *)data, 1);
114 }
115 
116 /*
117  * interrupt
118  */
119 static void rtctimer_interrupt(void *private_data)
120 {
121         tasklet_schedule(private_data);
122 }
123 
124 
125 /*
126  *  ENTRY functions
127  */
128 static 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 
165 static 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  */
177 module_init(rtctimer_init)
178 module_exit(rtctimer_exit)
179 
180 module_param(rtctimer_freq, int, 0444);
181 MODULE_PARM_DESC(rtctimer_freq, "timer frequency in Hz");
182 
183 MODULE_LICENSE("GPL");
184 
185 MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_RTC));
186 
187 #endif /* IS_ENABLED(CONFIG_RTC) */
188 

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