/*
 * Copyright (c) 1995-1999 The University of Utah and the Flux Group.
 * 
 * This file is part of the OSKit Linux Glue Libraries, which are free
 * software, also known as "open source;" you can redistribute them and/or
 * modify them under the terms of the GNU General Public License (GPL),
 * version 2, as published by the Free Software Foundation (FSF).
 * 
 * The OSKit is distributed in the hope that it will be useful, but WITHOUT ANY
 * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GPL for more details.  You should have
 * received a copy of the GPL along with the OSKit; see the file COPYING.  If
 * not, write to the FSF, 59 Temple Place #330, Boston, MA 02111-1307, USA.
 */

/*
 * Linux auto-irq support.
 */

/* Copyright (C) 1995 Shantanu Goel. */

/*
 *  Written 1994 by Donald Becker.
 *
 *  The author may be reached as becker@CESDIS.gsfc.nasa.gov, or C/O
 *  Center of Excellence in Space Data and Information Sciences
 *    Code 930.5, Goddard Space Flight Center, Greenbelt MD 20771
 *
 *  This code is a general-purpose IRQ line detector for devices with
 *  jumpered IRQ lines.  If you can make the device raise an IRQ (and
 *  that IRQ line isn't already being used), these routines will tell
 *  you what IRQ line it's using -- perfect for those oh-so-cool boot-time
 *  device probes!
 *
 *  To use this, first call autoirq_setup(timeout). TIMEOUT is how many
 *  'jiffies' (1/100 sec.) to detect other devices that have active IRQ lines,
 *  and can usually be zero at boot.  'autoirq_setup()' returns the bit
 *  vector of nominally-available IRQ lines (lines may be physically in-use,
 *  but not yet registered to a device).
 *  Next, set up your device to trigger an interrupt.
 *  Finally call autoirq_report(TIMEOUT) to find out which IRQ line was
 *  most recently active.  The TIMEOUT should usually be zero, but may
 *  be set to the number of jiffies to wait for a slow device to raise an IRQ.
 *
 *  The idea of using the setup timeout to filter out bogus IRQs came from
 *  the serial driver.
 */

#include <linux/sched.h>		/* jiffies */

#include <asm/bitops.h>			/* set_bit */
#include <asm/irq.h>			/* disable_irq */

/*
 * Set of fixed IRQs
 * (fpu, rtc, com1, PIC slave cascade, keyboard, timer).
 */
int irqs_busy = 0x2147;

static volatile int irq_number;	/* latest irq found */
static volatile int irq_bitmap;	/* bitmap of IRQs found */
static int irq_handled;		/* irq lines we have a handler on */

#if 0
extern unsigned long loops_per_sec;
#endif

#include "osenv.h"
#define HZ_NS		(1000000000 / HZ)

/*
 * Interrupt handler when probing an IRQ.
 */
static void
autoirq_probe(irq)
	int irq;
{
	/*
	 * Mark this IRQ as the last one
	 * that interrupted and disable it.
	 */
	irq_number = irq;
	set_bit(irq, (void *)&irq_bitmap);
	disable_irq(irq);
}

/*
 * Set up for auto-irq.
 */
int
autoirq_setup(waittime)
	int waittime;
{
	int i, mask;
#if 0
	int timeout = jiffies + waittime;
	int boguscount = (waittime * loops_per_sec) / 100;
#endif

	/*
	 * Allocate all possible IRQs.
	 */
	irq_handled = 0;
	for (i = 0; i < 16; i++) {
		if (test_bit(i, (void *)&irqs_busy) == 0
		    && request_irq(i, autoirq_probe, 0, 0, NULL) == 0)
			set_bit(i, (void *)&irq_handled);
	}

	irq_number = 0;
	irq_bitmap = 0;

	/*
	 * Hang out at least <waittime>
	 * jiffies waiting for bogus IRQ hits.
	 */
	osenv_timer_spin(waittime * HZ_NS);
#if 0
	while (timeout > jiffies && --boguscount > 0)
		;
#endif

	/*
	 * Free IRQs that caused bogus hits.
	 */
	for (i = 0, mask = 0x01; i < 16; i++, mask <<= 1) {
		if (irq_bitmap & irq_handled & mask) {
			irq_handled &= ~mask;
			free_irq(i, NULL);
		}
	}

	return (irq_handled);
}

/*
 * Return the last IRQ that caused an interrupt.
 */
int
autoirq_report(waittime)
	int waittime;
{
	int i;
	int timeout = jiffies + waittime;
#if 0
	int boguscount = (waittime * loops_per_sec) / 100;
#endif

	/*
	 * Hang out at least <waittime>
	 * jiffies waiting for the IRQ.
	 */
	while (!irq_number && timeout > jiffies)
		osenv_timer_spin(HZ_NS / 100); /* ??? */
#if 0
	while (timeout > jiffies && --boguscount > 0)
		if (irq_number)
			break;
#endif

	/*
	 * Retract the IRQ handlers that we handled.
	 */
	for (i = 0; i < 16; i++) {
		if (test_bit(i, (void *)&irq_handled))
			free_irq(i, NULL);
	}

	return (irq_number);
}