Nucleus

/*
 * This file deals with the Programmable Interrupt Controller.  It is usually
 * disabled and replaced by the Advanced Programmable Interrupt Controller.  It
 * is required to be enabled for the APIC to initialise, and can be used as a
 * fallback if there is no APIC in the system.
 */

#include <stdint.h>
#include <nucleus/io.h>

/* Initialise the PIT to a specified frequency */
static void
init_pit(uint32_t freq)
{
	uint32_t div = 1193182 / freq;
	outb(0x43, 0x36);
	outb(0x40, div & 0xFF);
	outb(0x40, (div >> 8) & 0xFF);
}

/* Initialise the PIC */
void
init_pic(void)
{
	/*
	 * By default interrupts and exceptions both start at IRQ#0.  To avoid
	 * collision interrupts are mapped to start at IRQ#32.  Since lower
	 * numbered IRQ lines are higher priority, exceptions have priority.
	 */
	outb(0x20, 0x11); io_wait();
	outb(0xA0, 0x11); io_wait();
	outb(0x21, 0x20); io_wait();
	outb(0xA1, 0x28); io_wait();
	outb(0x21, 0x04); io_wait();
	outb(0xA1, 0x02); io_wait();
	outb(0x21, 0x01); io_wait();
	outb(0xA1, 0x01); io_wait();
	outb(0x21, 0x00); io_wait();
	outb(0xA1, 0x00); io_wait();

	init_pit(1000);
}