sound/core/rtctimer.c

   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 <sound/driver.h>
  24 #include <linux/init.h>
  25 #include <linux/time.h>
  26 #include <linux/threads.h>
  27 #include <linux/interrupt.h>
  28 #include <linux/moduleparam.h>
  29 #include <sound/core.h>
  30 #include <sound/timer.h>
  31 #include <sound/info.h>
  32
  33 #if defined(CONFIG_RTC) || defined(CONFIG_RTC_MODULE)
  34
  35 #include <linux/mc146818rtc.h>
  36
  37 #define RTC_FREQ        1024            /* default frequency */
  38 #define NANO_SEC        1000000000L     /* 10^9 in sec */
  39
  40 /*
  41  * prototypes
  42  */
  43 static int rtctimer_open(snd_timer_t *t);
  44 static int rtctimer_close(snd_timer_t *t);
  45 static int rtctimer_start(snd_timer_t *t);
  46 static int rtctimer_stop(snd_timer_t *t);
  47
  48
  49 /*
  50  * The hardware dependent description for this timer.
  51  */
  52 static struct _snd_timer_hardware rtc_hw = {
  53         .flags =        SNDRV_TIMER_HW_FIRST|SNDRV_TIMER_HW_AUTO,
  54         .ticks =        100000000L,             /* FIXME: XXX */
  55         .open =         rtctimer_open,
  56         .close =        rtctimer_close,
  57         .start =        rtctimer_start,
  58         .stop =         rtctimer_stop,
  59 };
  60
  61 static int rtctimer_freq = RTC_FREQ;            /* frequency */
  62 static snd_timer_t *rtctimer;
  63 static atomic_t rtc_inc = ATOMIC_INIT(0);
  64 static rtc_task_t rtc_task;
  65
  66
  67 static int
  68 rtctimer_open(snd_timer_t *t)
  69 {
  70         int err;
  71
  72         err = rtc_register(&rtc_task);
  73         if (err < 0)
  74                 return err;
  75         t->private_data = &rtc_task;
  76         return 0;
  77 }
  78
  79 static int
  80 rtctimer_close(snd_timer_t *t)
  81 {
  82         rtc_task_t *rtc = t->private_data;
  83         if (rtc) {
  84                 rtc_unregister(rtc);
  85                 t->private_data = NULL;
  86         }
  87         return 0;
  88 }
  89
  90 static int
  91 rtctimer_start(snd_timer_t *timer)
  92 {
  93         rtc_task_t *rtc = timer->private_data;
  94         snd_assert(rtc != NULL, return -EINVAL);
  95         rtc_control(rtc, RTC_IRQP_SET, rtctimer_freq);
  96         rtc_control(rtc, RTC_PIE_ON, 0);
  97         atomic_set(&rtc_inc, 0);
  98         return 0;
  99 }
 100
 101 static int
 102 rtctimer_stop(snd_timer_t *timer)
 103 {
 104         rtc_task_t *rtc = timer->private_data;
 105         snd_assert(rtc != NULL, return -EINVAL);
 106         rtc_control(rtc, RTC_PIE_OFF, 0);
 107         return 0;
 108 }
 109
 110 /*
 111  * interrupt
 112  */
 113 static void rtctimer_interrupt(void *private_data)
 114 {
 115         int ticks;
 116
 117         atomic_inc(&rtc_inc);
 118         ticks = atomic_read(&rtc_inc);
 119         snd_timer_interrupt((snd_timer_t*)private_data, ticks);
 120         atomic_sub(ticks, &rtc_inc);
 121 }
 122
 123
 124 /*
 125  *  ENTRY functions
 126  */
 127 static int __init rtctimer_init(void)
 128 {
 129         int order, err;
 130         snd_timer_t *timer;
 131
 132         if (rtctimer_freq < 2 || rtctimer_freq > 8192) {
 133                 snd_printk(KERN_ERR "rtctimer: invalid frequency %d\n", rtctimer_freq);
 134                 return -EINVAL;
 135         }
 136         for (order = 1; rtctimer_freq > order; order <<= 1)
 137                 ;
 138         if (rtctimer_freq != order) {
 139                 snd_printk(KERN_ERR "rtctimer: invalid frequency %d\n", rtctimer_freq);
 140                 return -EINVAL;
 141         }
 142
 143         /* Create a new timer and set up the fields */
 144         err = snd_timer_global_new("rtc", SNDRV_TIMER_GLOBAL_RTC, &timer);
 145         if (err < 0)
 146                 return err;
 147
 148         strcpy(timer->name, "RTC timer");
 149         timer->hw = rtc_hw;
 150         timer->hw.resolution = NANO_SEC / rtctimer_freq;
 151
 152         /* set up RTC callback */
 153         rtc_task.func = rtctimer_interrupt;
 154         rtc_task.private_data = timer;
 155
 156         err = snd_timer_global_register(timer);
 157         if (err < 0) {
 158                 snd_timer_global_free(timer);
 159                 return err;
 160         }
 161         rtctimer = timer; /* remember this */
 162
 163         return 0;
 164 }
 165
 166 static void __exit rtctimer_exit(void)
 167 {
 168         if (rtctimer) {
 169                 snd_timer_global_unregister(rtctimer);
 170                 rtctimer = NULL;
 171         }
 172 }
 173
 174
 175 /*
 176  * exported stuff
 177  */
 178 module_init(rtctimer_init)
 179 module_exit(rtctimer_exit)
 180
 181 module_param(rtctimer_freq, int, 0444);
 182 MODULE_PARM_DESC(rtctimer_freq, "timer frequency in Hz");
 183
 184 MODULE_LICENSE("GPL");
 185
 186 MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_RTC));
 187
 188 #endif /* CONFIG_RTC || CONFIG_RTC_MODULE */