rockbox/firmware/target/sh/kernel-sh.c

/***************************************************************************
 *             __________               __   ___.
 *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
 *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
 *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
 *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
 *                     \/            \/     \/    \/            \/
 * $Id$
 *
 * Copyright (C) 2002 by Björn Stenberg
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ****************************************************************************/
#include "config.h"
#include "system.h"
#include "kernel.h"
#include "panic.h"

void tick_start(unsigned int interval_in_ms)
{
    unsigned long count;

    count = CPU_FREQ * interval_in_ms / 1000 / 8;

    if(count > 0x10000)
    {
        panicf("Error! The tick interval is too long (%d ms)\n",
               interval_in_ms);
        return;
    }
    
    /* We are using timer 0 */
    
    TSTR &= ~0x01; /* Stop the timer */
    TSNC &= ~0x01; /* No synchronization */
    TMDR &= ~0x01; /* Operate normally */

    TCNT0 = 0;   /* Start counting at 0 */
    GRA0 = (unsigned short)(count - 1);
    TCR0 = 0x23; /* Clear at GRA match, sysclock/8 */

    /* Enable interrupt on level 1 */
    IPRC = (IPRC & ~0x00f0) | 0x0010;
    
    TSR0 &= ~0x01;
    TIER0 = 0xf9; /* Enable GRA match interrupt */

    TSTR |= 0x01; /* Start timer 1 */
}

void IMIA0(void) __attribute__ ((interrupt_handler));
void IMIA0(void)
{
    /* Run through the list of tick tasks */
    call_tick_tasks();

    TSR0 &= ~0x01;
}