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Annotation of prex/sys/arch/i386/pc/clock.c, Revision 1.1

1.1     ! nbrk        1: /*-
        !             2:  * Copyright (c) 2005-2007, Kohsuke Ohtani
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution and use in source and binary forms, with or without
        !             6:  * modification, are permitted provided that the following conditions
        !             7:  * are met:
        !             8:  * 1. Redistributions of source code must retain the above copyright
        !             9:  *    notice, this list of conditions and the following disclaimer.
        !            10:  * 2. Redistributions in binary form must reproduce the above copyright
        !            11:  *    notice, this list of conditions and the following disclaimer in the
        !            12:  *    documentation and/or other materials provided with the distribution.
        !            13:  * 3. Neither the name of the author nor the names of any co-contributors
        !            14:  *    may be used to endorse or promote products derived from this software
        !            15:  *    without specific prior written permission.
        !            16:  *
        !            17:  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
        !            18:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            19:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            20:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
        !            21:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            22:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            23:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            24:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            25:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            26:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            27:  * SUCH DAMAGE.
        !            28:  */
        !            29:
        !            30: /*
        !            31:  * clock.c - clock driver
        !            32:  */
        !            33:
        !            34: #include <kernel.h>
        !            35: #include <timer.h>
        !            36: #include <irq.h>
        !            37: #include <locore.h>
        !            38:
        !            39: /* Interrupt vector for clock */
        !            40: #define CLOCK_IRQ      0
        !            41:
        !            42: /* The internal tick rate in ticks per second */
        !            43: #define PIT_TICK       1193180L
        !            44:
        !            45: /* The latch count value for the current HZ setting */
        !            46: #define PIT_LATCH      ((PIT_TICK + (HZ / 2)) / HZ)
        !            47:
        !            48: /* I/O port for programmable interval timer */
        !            49: #define PIT_CH0                0x40
        !            50: #define PIT_CTRL       0x43
        !            51:
        !            52: /*
        !            53:  * Clock interrupt service routine.
        !            54:  * No H/W reprogram is required.
        !            55:  */
        !            56: static int
        !            57: clock_isr(int irq)
        !            58: {
        !            59:
        !            60:        irq_lock();
        !            61:        timer_tick();
        !            62:        irq_unlock();
        !            63:
        !            64:        return INT_DONE;
        !            65: }
        !            66:
        !            67: /*
        !            68:  * Initialize clock H/W chip.
        !            69:  * Setup clock tick rate and install clock ISR.
        !            70:  */
        !            71: void
        !            72: clock_init(void)
        !            73: {
        !            74:        irq_t clock_irq;
        !            75:
        !            76:        outb_p(0x34, PIT_CTRL);         /* Command to set generator mode */
        !            77:        outb_p((u_char)(PIT_LATCH & 0xff), PIT_CH0);            /* LSB */
        !            78:        outb_p((u_char)((PIT_LATCH >> 8) & 0xff), PIT_CH0);     /* MSB */
        !            79:
        !            80:        clock_irq = irq_attach(CLOCK_IRQ, IPL_CLOCK, 0, &clock_isr, NULL);
        !            81:        ASSERT(clock_irq != NULL);
        !            82:
        !            83:        DPRINTF(("Clock rate: %d ticks/sec\n", CONFIG_HZ));
        !            84: }