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40 lines
932 B
C++
40 lines
932 B
C++
#include "pit.hpp"
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#include "idt.hpp"
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#include "portio.hpp"
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#include "tasking.hpp"
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static volatile std::uint32_t ticks = 0;
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static void timer_callback(const Registers& regs)
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{
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ticks = ticks + 1;
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schedule(const_cast<Registers&>(regs));
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}
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void pit_initialize(std::uint32_t frequency)
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{
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// Firstly, register our timer callback.
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idt_register_callback(32, timer_callback);
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// The value we send to the PIT is the value to divide it's input clock
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// (1193180 Hz) by, to get our required frequency. Important to note is
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// that the divisor must be small enough to fit into 16-bits.
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auto divisor = 1193180 / frequency;
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// Send the command byte.
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outb(0x43, 0x36);
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// Send the frequency divisor.
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outb(0x40, divisor & 0xFF);
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outb(0x40, (divisor >> 8) & 0xFF);
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}
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void pit_busy_wait(std::int32_t tks)
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{
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const auto end = ticks + tks;
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while (end - ticks > 0)
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asm volatile("nop");
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}
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