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scoutos / prex-0.9.0 / bsp / hal / x86 / pc / clock.c @ 03e9c04a

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/*-
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 * Copyright (c) 2005-2007, Kohsuke Ohtani
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 * 1. Redistributions of source code must retain the above copyright
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 *    notice, this list of conditions and the following disclaimer.
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 * 2. Redistributions in binary form must reproduce the above copyright
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 *    notice, this list of conditions and the following disclaimer in the
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 *    documentation and/or other materials provided with the distribution.
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 * 3. Neither the name of the author nor the names of any co-contributors
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 *    may be used to endorse or promote products derived from this software
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 *    without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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 * SUCH DAMAGE.
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 */
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/*
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 * clock.c - clock driver for i8254.
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 */
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#include <kernel.h>
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#include <timer.h>
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#include <irq.h>
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#include <sys/ipl.h>
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#include <cpufunc.h>
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/* Interrupt vector for clock */
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#define CLOCK_IRQ        0
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/* The internal tick rate in ticks per second */
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#define PIT_TICK        1193180L
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/* The latch count value for the current HZ setting */
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#define PIT_LATCH        ((PIT_TICK + (HZ / 2)) / HZ)
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/* I/O port for programmable interval timer */
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#define PIT_CH0                0x40
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#define PIT_CTRL        0x43
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/*
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 * Clock interrupt service routine.
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 * No H/W reprogram is required.
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 */
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static int
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clock_isr(void *arg)
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{
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        int s;
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        s = splhigh();
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        timer_handler();
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        splx(s);
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        return INT_DONE;
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}
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/*
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 * Initialize clock H/W chip.
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 * Setup clock tick rate and install clock ISR.
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 */
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void
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clock_init(void)
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{
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        irq_t clock_irq;
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        outb_p(PIT_CTRL, 0x34);                /* Command to set generator mode */
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        outb_p(PIT_CH0, (u_char)(PIT_LATCH & 0xff));                /* LSB */
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        outb_p(PIT_CH0, (u_char)((PIT_LATCH >> 8) & 0xff));        /* MSB */
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        clock_irq = irq_attach(CLOCK_IRQ, IPL_CLOCK, 0, &clock_isr,
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                               IST_NONE, NULL);
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        DPRINTF(("Clock rate: %d ticks/sec\n", CONFIG_HZ));
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}