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root/bsp/hal/x86/pc/clock.c

DEFINITIONS

1. clock_isr
2. clock_init

   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  */
  30 /*
  31  * clock.c - clock driver for i8254.
  32  */
  34 #include <kernel.h>
  35 #include <timer.h>
  36 #include <irq.h>
  37 #include <sys/ipl.h>
  38 #include <cpufunc.h>
  40 /* Interrupt vector for clock */
  41 #define CLOCK_IRQ       0
  43 /* The internal tick rate in ticks per second */
  44 #define PIT_TICK        1193180L
  46 /* The latch count value for the current HZ setting */
  47 #define PIT_LATCH       ((PIT_TICK + (HZ / 2)) / HZ)
  49 /* I/O port for programmable interval timer */
  50 #define PIT_CH0         0x40
  51 #define PIT_CTRL        0x43
  53 /*
  54  * Clock interrupt service routine.
  55  * No H/W reprogram is required.
  56  */
  57 static int
clock_isr(void *arg)
  59 {
  60         int s;
s = splhigh();
timer_handler();
splx(s);
  66         return INT_DONE;
  67 }
  69 /*
  70  * Initialize clock H/W chip.
  71  * Setup clock tick rate and install clock ISR.
  72  */
  73 void
clock_init(void)
  75 {
irq_t clock_irq;
outb_p(PIT_CTRL, 0x34);         /* Command to set generator mode */
outb_p(PIT_CH0, (u_char)(PIT_LATCH & 0xff));            /* LSB */
outb_p(PIT_CH0, (u_char)((PIT_LATCH >> 8) & 0xff));     /* MSB */
clock_irq = irq_attach(CLOCK_IRQ, IPL_CLOCK, 0, &clock_isr,
IST_NONE, NULL);
DPRINTF(("Clock rate: %d ticks/sec\n", CONFIG_HZ));
  86 }