Colony » Colony Scout » Colony Scout OS

/*-

 * Copyright (c) 2005-2007, Kohsuke Ohtani

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 * 1. Redistributions of source code must retain the above copyright

 *    notice, this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright

 *    notice, this list of conditions and the following disclaimer in the

 *    documentation and/or other materials provided with the distribution.

 * 3. Neither the name of the author nor the names of any co-contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND

 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE

 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

 * SUCH DAMAGE.

 */

/*

 * clock.c - clock driver

 */

#include <sys/ipl.h>

#include <kernel.h>

#include <timer.h>

#include <irq.h>

#include <cpufunc.h>

/* Interrupt vector for timer (TMR0 of GBA) */

#define CLOCK_IRQ        3

/* The clock rate per second ... 2^24 */

#define CLOCK_RATE        16777216L

/* The initial counter value */

#define TIMER_COUNT        (0xffff - (CLOCK_RATE / 64 / HZ))

/* GBA timer registers */

#define TMR0_COUNT        (*(volatile uint16_t *)0x4000100)

#define TMR0_CTRL        (*(volatile uint16_t *)0x4000102)

/* Timer frequency */

#define TMR_1_CLOCK        0x0000

#define TMR_64_CLOCK        0x0001

#define TMR_256_CLOCK        0x0002

#define TMR_1024_CLOCK        0x0003

/* Cascade switch */

#define TMR_CASCADE        0x0004

/* Interrupt for overflow */

#define        TMR_IRQEN        0x0040

/* Timer switch */

#define TMR_EN                0x0080

/*

 * Clock interrupt service routine.

 * No H/W reprogram is required.

 */

static int

clock_isr(void *arg)

{

        splhigh();

        timer_handler();

        spl0();

        return INT_DONE;

}

/*

 * Initialize clock H/W chip.

 * Setup clock tick rate and install clock ISR.

 */

void

clock_init(void)

{

        irq_t clock_irq;

        /* Setup counter value */

        TMR0_COUNT = TIMER_COUNT;

        TMR0_CTRL = (uint16_t)(TMR_IRQEN | TMR_64_CLOCK);

        /* Install ISR */

        clock_irq = irq_attach(CLOCK_IRQ, IPL_CLOCK, 0, &clock_isr,

                               IST_NONE, NULL);

        /* Enable timer */

        TMR0_CTRL |= TMR_EN;

}