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Annotation of prex/sys/arch/i386/pc/clock.c, Revision 1.1.1.1

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: }