firmware/target/arm/tcc780x/timer-tcc780x.c

   1 /***************************************************************************
   2 *             __________               __   ___.
   3 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7 *                     \/            \/     \/    \/            \/
   8 * $Id$
   9 *
  10 * Copyright (C) 2008 by Rob Purchase
  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
  22 #include "config.h"
  23 #include "cpu.h"
  24 #include "system.h"
  25 #include "timer.h"
  26 #include "logf.h"
  27
  28 static const int prescale_shifts[] = {1, 2, 3, 4, 5, 10, 12};
  29
  30 bool __timer_set(long cycles, bool start)
  31 {
  32     bool found = false;
  33
  34     int prescale_option = 0;
  35     int actual_cycles = 0;
  36
  37     /* Use the first prescale that fits Timer4's 20-bit counter */
  38     while (!found && prescale_option < 7)
  39     {
  40         actual_cycles = cycles >> prescale_shifts[prescale_option];
  41
  42         if (actual_cycles < 0x100000)
  43             found = true;
  44         else
  45             prescale_option++;
  46     }
  47
  48     if (!found)
  49         return false;
  50
  51     /* Stop the timer and set new prescale & ref count */
  52     TCFG(4) &= ~TCFG_EN;
  53     TCFG(4) = prescale_option << TCFG_SEL;
  54     TREF(4) = actual_cycles;
  55
  56     if (start && pfn_unregister != NULL)
  57     {
  58         pfn_unregister();
  59         pfn_unregister = NULL;
  60     }
  61
  62     return true;
  63 }
  64
  65 bool __timer_register(void)
  66 {
  67     int oldstatus = disable_interrupt_save(IRQ_STATUS);
  68
  69     TCFG(4) |= TCFG_CLEAR | TCFG_IEN | TCFG_EN;
  70
  71     restore_interrupt(oldstatus);
  72
  73     return true;
  74 }
  75
  76 void __timer_unregister(void)
  77 {
  78     int oldstatus = disable_interrupt_save(IRQ_STATUS);
  79
  80     TCFG(4) &= ~TCFG_EN;
  81
  82     restore_interrupt(oldstatus);
  83 }