/* 
 * Copyright 2010 Stefan Lankes, Chair for Operating Systems,
 *                               RWTH Aachen University
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * This file is part of MetalSVM.
 */

#include <metalsvm/string.h>
#include <metalsvm/tasks.h>
#include <asm/irq.h>
#include <asm/idt.h>
#include <asm/isrs.h>

/* 
 * These are own ISRs that point to our special IRQ handler
 * instead of the regular 'fault_handler' function 
 */
extern void irq0(void);
extern void irq1(void);
extern void irq2(void);
extern void irq3(void);
extern void irq4(void);
extern void irq5(void);
extern void irq6(void);
extern void irq7(void);
extern void irq8(void);
extern void irq9(void);
extern void irq10(void);
extern void irq11(void);
extern void irq12(void);
extern void irq13(void);
extern void irq14(void);
extern void irq15(void);

/*
 * This array is actually an array of function pointers. We use
 * this to handle custom IRQ handlers for a given IRQ
 */
static void *irq_routines[16] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 };

/* This installs a custom IRQ handler for the given IRQ */
void irq_install_handler(unsigned int irq, irq_handler_t handler)
{
	irq_routines[irq] = handler;
}

/* This clears the handler for a given IRQ */
void irq_uninstall_handler(unsigned int irq)
{
	irq_routines[irq] = NULL;
}

/* 
 * Normally, IRQs 0 to 7 are mapped to entries 8 to 15. This
 * is a problem in protected mode, because IDT entry 8 is a
 * Double Fault! Without remapping, every time IRQ0 fires,
 * you get a Double Fault Exception, which is NOT actually
 * what's happening. We send commands to the Programmable
 * Interrupt Controller (PICs - also called the 8259's) in
 * order to make IRQ0 to 15 be remapped to IDT entries 32 to
 * 47 
 */
static void irq_remap(void)
{
	outportb(0x20, 0x11);
	outportb(0xA0, 0x11);
	outportb(0x21, 0x20);
	outportb(0xA1, 0x28);
	outportb(0x21, 0x04);
	outportb(0xA1, 0x02);
	outportb(0x21, 0x01);
	outportb(0xA1, 0x01);
	outportb(0x21, 0x0);
	outportb(0xA1, 0x0);
}

/*
 * We first remap the interrupt controllers, and then we install
 * the appropriate ISRs to the correct entries in the IDT. This
 * is just like installing the exception handlers
 */
static void irq_install(void)
{
	irq_remap();
	idt_set_gate(32, (unsigned)irq0, 0x08, 0x8E);
	idt_set_gate(33, (unsigned)irq1, 0x08, 0x8E);
	idt_set_gate(34, (unsigned)irq2, 0x08, 0x8E);
	idt_set_gate(35, (unsigned)irq3, 0x08, 0x8E);
	idt_set_gate(36, (unsigned)irq4, 0x08, 0x8E);
	idt_set_gate(37, (unsigned)irq5, 0x08, 0x8E);
	idt_set_gate(38, (unsigned)irq6, 0x08, 0x8E);
	idt_set_gate(39, (unsigned)irq7, 0x08, 0x8E);
	idt_set_gate(40, (unsigned)irq8, 0x08, 0x8E);
	idt_set_gate(41, (unsigned)irq9, 0x08, 0x8E);
	idt_set_gate(42, (unsigned)irq10, 0x08, 0x8E);
	idt_set_gate(43, (unsigned)irq11, 0x08, 0x8E);
	idt_set_gate(44, (unsigned)irq12, 0x08, 0x8E);
	idt_set_gate(45, (unsigned)irq13, 0x08, 0x8E);
	idt_set_gate(46, (unsigned)irq14, 0x08, 0x8E);
	idt_set_gate(47, (unsigned)irq15, 0x08, 0x8E);
}

void irq_init(void)
{
	idt_install();
	isrs_install();
	irq_install();
}

/* 
 * Each of the IRQ ISRs point to this function, rather than
 * the 'fault_handler' in 'isrs.c'. The IRQ Controllers need
 * to be told when you are done servicing them, so you need
 * to send them an "End of Interrupt" command (0x20). There
 * are two 8259 chips: The first exists at 0x20, the second
 * exists at 0xA0. If the second controller (an IRQ from 8 to
 * 15) gets an interrupt, you need to acknowledge the
 * interrupt at BOTH controllers, otherwise, you only send
 * an EOI command to the first controller. If you don't send
 * an EOI, you won't raise any more IRQs 
 */
void irq_handler(struct state *s)

{
	/* This is a blank function pointer */
	void (*handler) (struct state * s);

	/* 
	 * Find out if we have a custom handler to run for this
	 * IRQ, and then finally, run it 
	 */
	handler = irq_routines[s->int_no - 32];
	if (handler) {
		handler(s);
	}

	/* 
	 * If the IDT entry that was invoked was greater than 40
	 * (meaning IRQ8 - 15), then we need to send an EOI to
	 * the slave controller 
	 */
	if (s->int_no >= 40) {
		outportb(0xA0, 0x20);
	}

	/* 
	 * In either case, we need to send an EOI to the master
	 * interrupt controller too 
	 */
	outportb(0x20, 0x20);
}