63 lines
1.7 KiB
C
63 lines
1.7 KiB
C
#include <arch/irq.h>
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#include <arch/ports.h>
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#include <mango/clock.h>
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#include <mango/cpu.h>
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#include <mango/printk.h>
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#define PIT_COUNTER0 0x40
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#define PIT_CMD 0x43
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#define CMD_BINARY 0x00 // Use Binary counter values
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#define CMD_BCD 0x01 // Use Binary Coded Decimal counter values
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#define CMD_MODE0 0x00 // Interrupt on Terminal Count
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#define CMD_MODE1 0x02 // Hardware Retriggerable One-Shot
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#define CMD_MODE2 0x04 // Rate Generator
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#define CMD_MODE3 0x06 // Square Wave
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#define CMD_MODE4 0x08 // Software Trigerred Strobe
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#define CMD_MODE5 0x0a // Hardware Trigerred Strobe
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#define CMD_LATCH 0x00
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#define CMD_RW_LOW 0x10 // Least Significant Byte
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#define CMD_RW_HI 0x20 // Most Significant Byte
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#define CMD_RW_BOTH 0x30 // Least followed by Most Significant Byte
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#define CMD_COUNTER0 0x00
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#define CMD_COUNTER1 0x40
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#define CMD_COUNTER2 0x80
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#define CMD_READBACK 0xc0
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#define PIT_FREQUENCY 1193182
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static volatile unsigned long long ticks = 0;
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static int pit_callback(void)
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{
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clock_advance(1);
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ticks++;
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return 0;
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}
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static struct irq_hook pit_irq_hook = {.irq_callback = pit_callback};
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void pit_start(unsigned int hz)
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{
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hook_irq(IRQ0, &pit_irq_hook);
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unsigned int divisor = PIT_FREQUENCY / hz;
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outportb(PIT_CMD, CMD_BINARY | CMD_MODE2 | CMD_RW_BOTH | CMD_COUNTER0);
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outportb(PIT_COUNTER0, divisor);
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outportb(PIT_COUNTER0, divisor >> 8);
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}
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void pit_stop(void)
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{
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unsigned int divisor = PIT_FREQUENCY / 20;
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outportb(PIT_CMD, CMD_BINARY | CMD_MODE4 | CMD_RW_BOTH | CMD_COUNTER0);
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outportb(PIT_COUNTER0, divisor);
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outportb(PIT_COUNTER0, divisor >> 8);
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unhook_irq(IRQ0, &pit_irq_hook);
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}
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