lib_i386/timer.c

   1 /*
   2  * (C) Copyright 2002
   3  * Daniel Engström, Omicron Ceti AB, daniel@omicron.se.
   4  *
   5  * See file CREDITS for list of people who contributed to this
   6  * project.
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public License as
  10  * published by the Free Software Foundation; either version 2 of
  11  * the License, or (at your option) any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  21  * MA 02111-1307 USA
  22  */
  23
  24 #include <common.h>
  25 #include <malloc.h>
  26 #include <asm/io.h>
  27 #include <asm/i8254.h>
  28 #include <asm/ibmpc.h>
  29
  30 struct timer_isr_function {
  31         struct timer_isr_function *next;
  32         timer_fnc_t *isr_func;
  33 };
  34
  35 static struct timer_isr_function *first_timer_isr = NULL;
  36 static volatile unsigned long system_ticks = 0;
  37
  38 /*
  39  * register_timer_isr() allows multiple architecture and board specific
  40  * functions to be called every millisecond. Keep the execution time of
  41  * each function as low as possible
  42  */
  43 int register_timer_isr (timer_fnc_t *isr_func)
  44 {
  45         struct timer_isr_function *new_func;
  46         struct timer_isr_function *temp;
  47         int flag;
  48
  49         new_func = malloc(sizeof(struct timer_isr_function));
  50
  51         if (new_func == NULL)
  52                 return 1;
  53
  54         new_func->isr_func = isr_func;
  55         new_func->next = NULL;
  56
  57         /*
  58          *  Don't allow timer interrupts while the
  59          *  linked list is being modified
  60          */
  61         flag = disable_interrupts ();
  62
  63         if (first_timer_isr == NULL) {
  64                 first_timer_isr = new_func;
  65         } else {
  66                 temp = first_timer_isr;
  67                 while (temp->next != NULL)
  68                         temp = temp->next;
  69                 temp->next = new_func;
  70         }
  71
  72         if (flag)
  73                 enable_interrupts ();
  74
  75         return 0;
  76 }
  77
  78 /*
  79  * timer_isr() MUST be the registered interrupt handler for
  80  */
  81 void timer_isr(void *unused)
  82 {
  83         struct timer_isr_function *temp = first_timer_isr;
  84
  85         system_ticks++;
  86
  87         /* Execute each registered function */
  88         while (temp != NULL) {
  89                 temp->isr_func ();
  90                 temp = temp->next;
  91         }
  92 }
  93
  94 void reset_timer (void)
  95 {
  96         system_ticks = 0;
  97 }
  98
  99 ulong get_timer (ulong base)
 100 {
 101         return (system_ticks - base);
 102 }
 103
 104 void set_timer (ulong t)
 105 {
 106         system_ticks = t;
 107 }