firmware/target/arm/s3c2440/kernel-s3c2440.c

   1 /***************************************************************************
   2 *             __________               __   ___.
   3 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7 *                     \/            \/     \/    \/            \/
   8 * $Id$
   9 *
  10 * Copyright (C) 2007 by Michael Sevakis
  11 *
  12 * This program is free software; you can redistribute it and/or
  13 * modify it under the terms of the GNU General Public License
  14 * as published by the Free Software Foundation; either version 2
  15 * of the License, or (at your option) any later version.
  16 *
  17 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  18 * KIND, either express or implied.
  19 *
  20 ****************************************************************************/
  21 #include "config.h"
  22 #include "system.h"
  23 #include "kernel.h"
  24 #include "timer.h"
  25 #include "thread.h"
  26
  27 void tick_start(unsigned int interval_in_ms)
  28 {
  29     /*
  30      * Based on default PCLK of 49.1568MHz - scaling chosen to give
  31      * remainder-free result for tick interval of 10ms (100Hz)
  32      * Timer input clock frequency =
  33      *      fPCLK / {prescaler value+1} / {divider value}
  34      * TIMER_FREQ = 49156800 / 2
  35      * 146300 = TIMER_FREQ / 21 / 8
  36      * 49156800 = 19*11*(7)*7*5*5*(3)*2*2*2*2*2*2
  37      * 21 = 7*3
  38      */
  39
  40     /* stop timer 4 */
  41     TCON &= ~(1 << 20);
  42     /* Set the count for timer 4 */
  43     TCNTB4 = (TIMER_FREQ / TIMER234_PRESCALE / 8) * interval_in_ms / 1000;
  44     /* Set the the prescaler value for timers 2,3, and 4 */
  45     TCFG0 = (TCFG0 & ~0xff00) | ((TIMER234_PRESCALE-1) << 8);
  46     /* DMA mode off, MUX4 = 1/16 */
  47     TCFG1 = (TCFG1 & ~0xff0000) | 0x030000;
  48     /* set manual bit */
  49     TCON |= 1 << 21;
  50     /* reset manual bit */
  51     TCON &= ~(1 << 21);
  52
  53     /* interval mode */
  54     TCON |= 1 << 22;
  55     /* start timer 4 */
  56     TCON |= (1 << 20);
  57
  58     /* timer 4 unmask interrupts */
  59     INTMSK &= ~TIMER4_MASK;
  60 }
  61
  62 #ifdef BOOTLOADER
  63 void tick_stop(void)
  64 {
  65     s3c_regset32(&INTMSK, TIMER4_MASK);
  66     TCON &= ~(1 << 20);
  67     SRCPND = TIMER4_MASK;
  68     INTPND = TIMER4_MASK;
  69 }
  70 #endif
  71
  72 void TIMER4(void)
  73 {
  74     /* Run through the list of tick tasks */
  75     call_tick_tasks();
  76
  77     SRCPND = TIMER4_MASK;
  78     INTPND = TIMER4_MASK;
  79 }