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[/] [ao486/] [trunk/] [syn/] [components/] [ps2/] [software/] [exe_bsp/] [HAL/] [src/] [alt_tick.c] - Blame information for rev 2

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1 2 alfik
/******************************************************************************
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*                                                                             *
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* License Agreement                                                           *
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*                                                                             *
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* Copyright (c) 2004 Altera Corporation, San Jose, California, USA.           *
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* All rights reserved.                                                        *
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*                                                                             *
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* Permission is hereby granted, free of charge, to any person obtaining a     *
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* copy of this software and associated documentation files (the "Software"),  *
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* to deal in the Software without restriction, including without limitation   *
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,    *
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* and/or sell copies of the Software, and to permit persons to whom the       *
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* Software is furnished to do so, subject to the following conditions:        *
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*                                                                             *
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* The above copyright notice and this permission notice shall be included in  *
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* all copies or substantial portions of the Software.                         *
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*                                                                             *
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR  *
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,    *
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE *
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER      *
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING     *
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER         *
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* DEALINGS IN THE SOFTWARE.                                                   *
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*                                                                             *
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* This agreement shall be governed in all respects by the laws of the State   *
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* of California and by the laws of the United States of America.              *
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*                                                                             *
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* Altera does not recommend, suggest or require that this reference design    *
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* file be used in conjunction or combination with any other product.          *
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******************************************************************************/
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#include "sys/alt_irq.h"
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#include "sys/alt_alarm.h"
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#include "os/alt_hooks.h"
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#include "alt_types.h"
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/*
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 * "_alt_tick_rate" is used to store the value of the system clock frequency
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 * in ticks per second. It is initialised to zero, which corresponds to there
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 * being no system clock facility available.
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 */
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alt_u32 _alt_tick_rate = 0;
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/*
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 * "_alt_nticks" is the number of system clock ticks that have elapsed since
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 * reset.
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 */
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volatile alt_u32 _alt_nticks = 0;
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/*
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 * "alt_alarm_list" is the head of a linked list of registered alarms. This is
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 * initialised to be an empty list.
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 */
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ALT_LLIST_HEAD(alt_alarm_list);
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/*
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 * alt_alarm_stop() is called to remove an alarm from the list of registered
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 * alarms. Alternatively an alarm can unregister itself by returning zero when
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 * the alarm executes.
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 */
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void alt_alarm_stop (alt_alarm* alarm)
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{
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  alt_irq_context irq_context;
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  irq_context = alt_irq_disable_all();
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  alt_llist_remove (&alarm->llist);
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  alt_irq_enable_all (irq_context);
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}
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/*
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 * alt_tick() is periodically called by the system clock driver in order to
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 * process the registered list of alarms. Each alarm is registed with a
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 * callback interval, and a callback function, "callback".
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 *
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 * The return value of the callback function indicates how many ticks are to
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 * elapse until the next callback. A return value of zero indicates that the
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 * alarm should be deactivated.
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 *
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 * alt_tick() is expected to run at interrupt level.
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 */
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void alt_tick (void)
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{
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  alt_alarm* next;
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  alt_alarm* alarm = (alt_alarm*) alt_alarm_list.next;
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  alt_u32    next_callback;
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  /* update the tick counter */
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  _alt_nticks++;
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  /* process the registered callbacks */
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  while (alarm != (alt_alarm*) &alt_alarm_list)
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  {
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    next = (alt_alarm*) alarm->llist.next;
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    /*
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     * Upon the tick-counter rolling over it is safe to clear the
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     * roll-over flag; once the flag is cleared this (or subsequnt)
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     * tick events are enabled to generate an alarm event.
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     */
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    if ((alarm->rollover) && (_alt_nticks == 0))
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    {
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      alarm->rollover = 0;
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    }
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    /* if the alarm period has expired, make the callback */
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    if ((alarm->time <= _alt_nticks) && (alarm->rollover == 0))
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    {
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      next_callback = alarm->callback (alarm->context);
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      /* deactivate the alarm if the return value is zero */
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      if (next_callback == 0)
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      {
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        alt_alarm_stop (alarm);
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      }
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      else
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      {
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        alarm->time += next_callback;
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        /*
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         * If the desired alarm time causes a roll-over, set the rollover
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         * flag. This will prevent the subsequent tick event from causing
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         * an alarm too early.
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         */
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        if(alarm->time < _alt_nticks)
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        {
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          alarm->rollover = 1;
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        }
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      }
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    }
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    alarm = next;
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  }
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  /*
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   * Update the operating system specific timer facilities.
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   */
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  ALT_OS_TIME_TICK();
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}
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