Subversion Repositories ao486

/******************************************************************************

*                                                                             *

* License Agreement                                                           *

*                                                                             *

* Copyright (c) 2004 Altera Corporation, San Jose, California, USA.           *

* All rights reserved.                                                        *

*                                                                             *

* Permission is hereby granted, free of charge, to any person obtaining a     *

* copy of this software and associated documentation files (the "Software"),  *

* to deal in the Software without restriction, including without limitation   *

* the rights to use, copy, modify, merge, publish, distribute, sublicense,    *

* and/or sell copies of the Software, and to permit persons to whom the       *

* Software is furnished to do so, subject to the following conditions:        *

*                                                                             *

* The above copyright notice and this permission notice shall be included in  *

* all copies or substantial portions of the Software.                         *

*                                                                             *

* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR  *

* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,    *

* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE *

* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER      *

* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING     *

* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER         *

* DEALINGS IN THE SOFTWARE.                                                   *

*                                                                             *

* This agreement shall be governed in all respects by the laws of the State   *

* of California and by the laws of the United States of America.              *

*                                                                             *

* Altera does not recommend, suggest or require that this reference design    *

* file be used in conjunction or combination with any other product.          *

******************************************************************************/

#include "sys/alt_irq.h"

#include "sys/alt_alarm.h"

#include "os/alt_hooks.h"

#include "alt_types.h"

/*

 * "_alt_tick_rate" is used to store the value of the system clock frequency

 * in ticks per second. It is initialised to zero, which corresponds to there

 * being no system clock facility available.

 */

alt_u32 _alt_tick_rate = 0;

/*

 * "_alt_nticks" is the number of system clock ticks that have elapsed since

 * reset.

 */

volatile alt_u32 _alt_nticks = 0;

/*

 * "alt_alarm_list" is the head of a linked list of registered alarms. This is

 * initialised to be an empty list.

 */

ALT_LLIST_HEAD(alt_alarm_list);

/*

 * alt_alarm_stop() is called to remove an alarm from the list of registered

 * alarms. Alternatively an alarm can unregister itself by returning zero when

 * the alarm executes.

 */

void alt_alarm_stop (alt_alarm* alarm)

{

  alt_irq_context irq_context;

  irq_context = alt_irq_disable_all();

  alt_llist_remove (&alarm->llist);

  alt_irq_enable_all (irq_context);

}

/*

 * alt_tick() is periodically called by the system clock driver in order to

 * process the registered list of alarms. Each alarm is registed with a

 * callback interval, and a callback function, "callback".

 *

 * The return value of the callback function indicates how many ticks are to

 * elapse until the next callback. A return value of zero indicates that the

 * alarm should be deactivated.

 *

 * alt_tick() is expected to run at interrupt level.

 */

void alt_tick (void)

{

  alt_alarm* next;

  alt_alarm* alarm = (alt_alarm*) alt_alarm_list.next;

  alt_u32    next_callback;

  /* update the tick counter */

  _alt_nticks++;

  /* process the registered callbacks */

  while (alarm != (alt_alarm*) &alt_alarm_list)

  {

    next = (alt_alarm*) alarm->llist.next;

    /*

     * Upon the tick-counter rolling over it is safe to clear the

     * roll-over flag; once the flag is cleared this (or subsequnt)

     * tick events are enabled to generate an alarm event.

     */

    if ((alarm->rollover) && (_alt_nticks == 0))

    {

      alarm->rollover = 0;

    }

    /* if the alarm period has expired, make the callback */

    if ((alarm->time <= _alt_nticks) && (alarm->rollover == 0))

    {

      next_callback = alarm->callback (alarm->context);

      /* deactivate the alarm if the return value is zero */

      if (next_callback == 0)

      {

        alt_alarm_stop (alarm);

      }

      else

      {

        alarm->time += next_callback;

        /*

         * If the desired alarm time causes a roll-over, set the rollover

         * flag. This will prevent the subsequent tick event from causing

         * an alarm too early.

         */

        if(alarm->time < _alt_nticks)

        {

          alarm->rollover = 1;

        }

      }

    }

    alarm = next;

  }

  /*

   * Update the operating system specific timer facilities.

   */

  ALT_OS_TIME_TICK();

}