/*
* include/asm-mips/i8259.h
*
* i8259A interrupt definitions.
*
* Copyright (C) 2003 Maciej W. Rozycki
* Copyright (C) 2003 Ralf Baechle <[email protected]>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#ifndef _ASM_I8259_H
#define _ASM_I8259_H

#include <linux/compiler.h>
#include <linux/spinlock.h>

#include <asm/io.h>
#include <irq.h>

/* i8259A PIC registers */
#define PIC_MASTER_CMD 0x20
#define PIC_MASTER_IMR 0x21
#define PIC_MASTER_ISR PIC_MASTER_CMD
#define PIC_MASTER_POLL PIC_MASTER_ISR
#define PIC_MASTER_OCW3 PIC_MASTER_ISR
#define PIC_SLAVE_CMD 0xa0
#define PIC_SLAVE_IMR 0xa1

/* i8259A PIC related value */
#define PIC_CASCADE_IR 2
#define MASTER_ICW4_DEFAULT 0x01
#define SLAVE_ICW4_DEFAULT 0x01
#define PIC_ICW4_AEOI 2

extern raw_spinlock_t i8259A_lock;

extern int i8259A_irq_pending(unsigned int irq);
extern void make_8259A_irq(unsigned int irq);

extern void init_i8259_irqs(void);

/*
* Do the traditional i8259 interrupt polling thing. This is for the few
* cases where no better interrupt acknowledge method is available and we
* absolutely must touch the i8259.
*/
static inline int i8259_irq(void)
{
int irq;

raw_spin_lock(&i8259A_lock);

/* Perform an interrupt acknowledge cycle on controller 1. */
outb(0x0C, PIC_MASTER_CMD); /* prepare for poll */
irq = inb(PIC_MASTER_CMD) & 7;
if (irq == PIC_CASCADE_IR) {
/*
* Interrupt is cascaded so perform interrupt
* acknowledge on controller 2.
*/
outb(0x0C, PIC_SLAVE_CMD); /* prepare for poll */
irq = (inb(PIC_SLAVE_CMD) & 7) + 8;
}

if (unlikely(irq == 7)) {
/*
* This may be a spurious interrupt.
*
* Read the interrupt status register (ISR). If the most
* significant bit is not set then there is no valid
* interrupt.
*/
outb(0x0B, PIC_MASTER_ISR); /* ISR register */
if(~inb(PIC_MASTER_ISR) & 0x80)
irq = -1;
}

raw_spin_unlock(&i8259A_lock);

return likely(irq >= 0) ? irq + I8259A_IRQ_BASE : irq;
}

#endif /* _ASM_I8259_H */