110 lines
3.4 KiB
C
110 lines
3.4 KiB
C
/*
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* Copyright (c) 2010, Stefan Lankes, RWTH Aachen University
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <eduos/stdio.h>
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#include <eduos/string.h>
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#include <eduos/tasks.h>
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#include <eduos/time.h>
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#include <eduos/errno.h>
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#include <asm/irq.h>
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#include <asm/irqflags.h>
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#include <asm/vga.h>
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#include <asm/io.h>
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/*
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* This will keep track of how many ticks the system
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* has been running for
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*/
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static volatile uint64_t timer_ticks = 0;
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uint64_t get_clock_tick(void)
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{
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return timer_ticks;
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}
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/*
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* Handles the timer. In this case, it's very simple: We
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* increment the 'timer_ticks' variable every time the
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* timer fires.
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*/
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static void timer_handler(struct state *s)
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{
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/* Increment our 'tick counter' */
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timer_ticks++;
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/*
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* Every TIMER_FREQ clocks (approximately 1 second), we will
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* display a message on the screen
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*/
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//if (timer_ticks % TIMER_FREQ == 0) {
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// vga_puts("One second has passed\n");
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//}
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}
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#define LATCH(f) ((CLOCK_TICK_RATE + f/2) / f)
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#define WAIT_SOME_TIME() do { uint64_t start = rdtsc(); \
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while(rdtsc() - start < 1000000) ; \
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} while (0)
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/*
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* Sets up the system clock by installing the timer handler
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* into IRQ0
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*/
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int timer_init(void)
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{
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/*
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* Installs 'timer_handler' for the PIC and APIC timer,
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* only one handler will be later used.
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*/
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irq_install_handler(32, timer_handler);
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irq_install_handler(123, timer_handler);
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/*
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* Port 0x43 is for initializing the PIT:
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*
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* 0x34 means the following:
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* 0b... (step-by-step binary representation)
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* ... 00 - channel 0
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* ... 11 - write two values to counter register:
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* first low-, then high-byte
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* ... 010 - mode number 2: "rate generator" / frequency divider
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* ... 0 - binary counter (the alternative is BCD)
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*/
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outportb(0x43, 0x34);
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WAIT_SOME_TIME();
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/* Port 0x40 is for the counter register of channel 0 */
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outportb(0x40, LATCH(TIMER_FREQ) & 0xFF); /* low byte */
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WAIT_SOME_TIME();
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outportb(0x40, LATCH(TIMER_FREQ) >> 8); /* high byte */
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return 0;
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}
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