81 lines
1.6 KiB
C
81 lines
1.6 KiB
C
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/*
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Copyright (C) 2015-2019 The University of Notre Dame
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This software is distributed under the GNU General Public License.
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See the file LICENSE for details.
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*/
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#include "interrupt.h"
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#include "clock.h"
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#include "ioports.h"
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#include "process.h"
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// Minimum PIT frequency is 18.2Hz.
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#define CLICKS_PER_SECOND 20
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#define TIMER0 0x40
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#define TIMER_MODE 0x43
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#define SQUARE_WAVE 0x36
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#define TIMER_FREQ 1193182
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#define TIMER_COUNT (((unsigned)TIMER_FREQ)/CLICKS_PER_SECOND)
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static uint32_t clicks = 0;
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static uint32_t seconds = 0;
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static struct list queue = { 0, 0 };
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static void clock_interrupt(int i, int code)
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{
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clicks++;
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process_wakeup_all(&queue);
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if(clicks >= CLICKS_PER_SECOND) {
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clicks = 0;
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seconds++;
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process_preempt();
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}
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}
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clock_t clock_read()
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{
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clock_t result;
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result.seconds = seconds;
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result.millis = 1000 * clicks / CLICKS_PER_SECOND;
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return result;
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}
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clock_t clock_diff(clock_t start, clock_t stop)
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{
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clock_t result;
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if(stop.millis < start.millis) {
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stop.millis += 1000;
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stop.seconds -= 1;
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}
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result.seconds = stop.seconds - start.seconds;
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result.millis = stop.millis - start.millis;
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return result;
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}
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void clock_wait(uint32_t millis)
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{
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clock_t start, elapsed;
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uint32_t total;
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start = clock_read();
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do {
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process_wait(&queue);
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elapsed = clock_diff(start, clock_read());
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total = elapsed.millis + elapsed.seconds * 1000;
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} while(total < millis);
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}
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void clock_init()
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{
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outb(SQUARE_WAVE, TIMER_MODE);
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outb((TIMER_COUNT & 0xff), TIMER0);
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outb((TIMER_COUNT >> 8) & 0xff, TIMER0);
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interrupt_register(32, clock_interrupt);
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interrupt_enable(32);
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printf("clock: ticking\n");
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}
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