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 <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) */