rockbox/firmware/target/sh/archos/timer-archos.c

/***************************************************************************
*             __________               __   ___.
*   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
*   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
*   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
*   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
*                     \/            \/     \/    \/            \/
* $Id$
*
* Copyright (C) 2005 Jens Arnold
*
* 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 "cpu.h"
#include "system.h"
#include "timer.h"

void IMIA4(void) __attribute__((interrupt_handler));
void IMIA4(void)
{
    if (pfn_timer != NULL)
        pfn_timer();
    and_b(~0x01, &TSR4); /* clear the interrupt */
}

bool timer_set(long cycles, bool start)
{
    int phi = 0; /* bits for the prescaler */
    int prescale = 1;

    while (cycles > 0x10000)
    {   /* work out the smallest prescaler that makes it fit */
        phi++;
        prescale <<= 1;
        cycles >>= 1;
    }

    if (prescale > 8)
        return false;

    if (start)
    {
        if (pfn_unregister != NULL)
        {
            pfn_unregister();
            pfn_unregister = NULL;
        }

        and_b(~0x10, &TSTR); /* Stop the timer 4 */
        and_b(~0x10, &TSNC); /* No synchronization */
        and_b(~0x10, &TMDR); /* Operate normally */

        TIER4 = 0xF9;        /* Enable GRA match interrupt */
    }

    TCR4 = 0x20 | phi;   /* clear at GRA match, set prescaler */
    GRA4 = (unsigned short)(cycles - 1);
    if (start || (TCNT4 >= GRA4))
        TCNT4 = 0;
    and_b(~0x01, &TSR4); /* clear an eventual interrupt */

    return true;
}

bool timer_start(void)
{
    IPRD = (IPRD & 0xFF0F) | 1 << 4;  /* interrupt priority */
    or_b(0x10, &TSTR); /* start timer 4 */
    return true;
}

void timer_stop(void)
{
    and_b(~0x10, &TSTR);    /* stop the timer 4 */
    IPRD = (IPRD & 0xFF0F); /* disable interrupt */
}