Annotation of prex-old/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 <cpu.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: int 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 != -1);
! 82:
! 83: printk("Clock rate: %d ticks/sec\n", CONFIG_HZ);
! 84: }
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