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heads up! implement SA-110 hardware clocks and interrupt controller glue.
only basic operations are implemented, but it should be sufficient to allow
driver module to use interrupts for device drivers

/*-
 * Copyright (c) 2005-2007, Kohsuke Ohtani
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the author nor the names of any co-contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * interrupt.c - interrupt handling routines for StrongARM-110 INTC.
 */

#include <kernel.h>
#include <irq.h>
#include <locore.h>

/* Registers for interrupt control unit */
#define SAIC_BASE	0x90050000
#define  SAIC_ICIP	0
#define  SAIC_ICMR	0x04
#define  SAIC_ICLR	0x08
#define  SAIC_ICFP	0x10
#define  SAIC_ICPR	0x20
#define  SAIC_ICCR	0x0c

/*
 * Interrupt line routing (CPU IRQ/FIQ)
 */
#define IMODE_CPUIRQ	0
#define IMODE_CPUFIQ	1

/*
 * Interrupt priority level
 *
 * Each interrupt has its logical priority level, with 0 being the highest
 * priority. While some ISR is running, all lower priority interrupts
 * are masked off.
 */
volatile int irq_level;

/*
 * Interrupt mapping table
 */
static int ipl_table[NIRQS];		/* Vector -> level */
static uint32_t mask_table[NIPLS];	/* Level -> mask */
 
void	saic_updatemask(uint32_t mask);
void	saic_routeto(int intrno, int irqfiq);

/*
 * Set mask for current ipl
 */
#define interrupt_updatemask()	saic_updatemask(mask_table[irq_level]);

/*
 * Write new mask to Mask Register.
 */
void
saic_updatemask(uint32_t mask)
{
	/* XXX */
	*(volatile uint32_t *)(SAIC_BASE + SAIC_ICMR) = mask;
}

/*
 * Interrupt line routing to IRQ/FIQ.
 */
void
saic_routeto(int intrno, int irqfiq)
{
	uint32_t bits;


	bits = *(volatile uint32_t *)(SAIC_BASE + SAIC_ICLR);

	switch(irqfiq) {
		case IMODE_CPUIRQ:
			bits &= ~(1 << intrno);
			break;

		case IMODE_CPUFIQ:
			bits |= 1 << intrno;
			break;

		default:
			panic("saic_routeto: bogus irqfiq %u for intr %u", irqfiq, intrno);
			/* NOTREACHED */
	}
}

/*
 * Unmask interrupt in PIC for specified irq.
 * The interrupt mask table is also updated.
 * Assumed CPU interrupt is disabled in caller.
 */
void
interrupt_unmask(int vector, int level)
{
	int i;
	uint32_t unmask = 1 << vector;

	ipl_table[vector] = level;
	/*
	 * Unmask target interrupt for all
	 * lower interrupt levels.
	 */
	for (i = 0; i < level; i++)
		mask_table[i] |= unmask;

	interrupt_updatemask();
}

/*
 * Mask interrupt in PIC for specified irq.
 * Interrupt must be disabled when this routine is called.
 */
void
interrupt_mask(int vector)
{
	int i, level;
	uint32_t mask = (uint32_t)~(1 << vector);

	level = ipl_table[vector];
	for (i = 0; i < level; i++)
		mask_table[i] &= mask;

	ipl_table[vector] = IPL_NONE;

	interrupt_updatemask();
}

/*
 * Setup interrupt mode.
 * Select whether an interrupt trigger is edge or level.
 */
void
interrupt_setup(int vector, int mode)
{
	/* nop */
}

/*
 * Dispatch interrupt
 *
 */
void
interrupt_dispatch(int vector)
{
	int old_ipl;

	printk("interrupt_dispatch()\n");

	/* Save & update interrupt level */
	old_ipl = irq_level;
	irq_level = ipl_table[vector];
	interrupt_updatemask();

	/* Allow another interrupt that has higher priority */
	interrupt_enable();

	/* Dispatch interrupt */
	irq_handler(vector);

	interrupt_disable();

	/* Restore interrupt level */
	irq_level = old_ipl;
	interrupt_updatemask();
}

/*
 * Common interrupt handler.
 * Our task is to scan active pending intrs and dispatch them.
 */
void
interrupt_handler(void)
{
	uint32_t bits;
	int vector;


	/* XXX we use only IRQs for now, so don't count FIQs */
	bits = *(volatile uint32_t *)(SAIC_BASE + SAIC_ICIP);

	/* dispatch all pending interrupts */
	for (vector = 0; vector < NIRQS; vector++) {
		if (bits & (1 << vector))
			interrupt_dispatch(vector);

		/* XXX pending intr clears within interrupting device */
	}

}

/*
 * Initialize interrupt controllers.
 * All interrupts will be masked off and routed to CPU IRQ line.
 */
void
interrupt_init(void)
{
	int i;

	interrupt_disable();

	irq_level = IPL_NONE;

	for (i = 0; i < NIRQS; i++)
		ipl_table[i] = IPL_NONE;

	for (i = 0; i < NIPLS; i++)
		mask_table[i] = 0;

	/*
	 * XXX route all Interrupt Controller interrupts to CPU IRQ line.
	 */
	for (i = 0; i < NIRQS; i++)
		saic_routeto(i, IMODE_CPUIRQ);

	interrupt_updatemask();

	interrupt_enable();
}