9a72bfc4cd
We only support 4 total chain entries at the moment, but that can be "easily expanded"... We don't really have a lite dynamic vector, just the big fat dynamic lists, so improving on this needs some extra effort. This commit also drags in a bunch of random network work by necessity.
91 lines
2.1 KiB
C
91 lines
2.1 KiB
C
/* vim: tabstop=4 shiftwidth=4 noexpandtab
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* This file is part of ToaruOS and is released under the terms
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* of the NCSA / University of Illinois License - see LICENSE.md
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* Copyright (C) 2011-2013 Kevin Lange
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*
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* Programmable Interrupt Timer
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*/
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#include <system.h>
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#include <logging.h>
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#include <process.h>
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#define PIT_A 0x40
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#define PIT_B 0x41
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#define PIT_C 0x42
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#define PIT_CONTROL 0x43
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#define PIT_MASK 0xFF
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#define PIT_SCALE 1193180
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#define PIT_SET 0x36
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#define TIMER_IRQ 0
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#define SUBTICKS_PER_TICK 1000
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#define RESYNC_TIME 1
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/*
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* Set the phase (in hertz) for the Programmable
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* Interrupt Timer (PIT).
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*/
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void
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timer_phase(
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int hz
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) {
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int divisor = PIT_SCALE / hz;
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outportb(PIT_CONTROL, PIT_SET);
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outportb(PIT_A, divisor & PIT_MASK);
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outportb(PIT_A, (divisor >> 8) & PIT_MASK);
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}
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/*
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* Internal timer counters
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*/
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unsigned long timer_ticks = 0;
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unsigned long timer_subticks = 0;
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signed long timer_drift = 0;
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signed long _timer_drift = 0;
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static int behind = 0;
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/*
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* IRQ handler for when the timer fires
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*/
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int timer_handler(struct regs *r) {
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if (++timer_subticks == SUBTICKS_PER_TICK || (behind && ++timer_subticks == SUBTICKS_PER_TICK)) {
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timer_ticks++;
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timer_subticks = 0;
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if (timer_ticks % RESYNC_TIME == 0) {
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uint32_t new_time = read_cmos();
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_timer_drift = new_time - boot_time - timer_ticks;
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if (_timer_drift > 0) behind = 1;
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else behind = 0;
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}
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}
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irq_ack(TIMER_IRQ);
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wakeup_sleepers(timer_ticks, timer_subticks);
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switch_task(1);
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return 1;
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}
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void relative_time(unsigned long seconds, unsigned long subseconds, unsigned long * out_seconds, unsigned long * out_subseconds) {
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if (subseconds + timer_subticks > SUBTICKS_PER_TICK) {
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*out_seconds = timer_ticks + seconds + 1;
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*out_subseconds = (subseconds + timer_subticks) - SUBTICKS_PER_TICK;
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} else {
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*out_seconds = timer_ticks + seconds;
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*out_subseconds = timer_subticks + subseconds;
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}
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}
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/*
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* Device installer for the PIT
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*/
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void timer_install(void) {
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debug_print(NOTICE,"Initializing interval timer");
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boot_time = read_cmos();
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irq_install_handler(TIMER_IRQ, timer_handler);
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timer_phase(SUBTICKS_PER_TICK); /* 100Hz */
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}
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