i8259.c

/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Code to handle x86 style IRQs plus some generic interrupt stuff.
 *
 * Copyright (C) 1992 Linus Torvalds
 * Copyright (C) 1994 - 2000 Ralf Baechle
 */
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/irqdomain.h>
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/syscore_ops.h>
#include <linux/irq.h>

#include <asm/i8259.h>
#include <asm/io.h>

/*
 * This is the 'legacy' 8259A Programmable Interrupt Controller,
 * present in the majority of PC/AT boxes.
 * plus some generic x86 specific things if generic specifics makes
 * any sense at all.
 * this file should become arch/i386/kernel/irq.c when the old irq.c
 * moves to arch independent land
 */

static int i8259A_auto_eoi = -1;
DEFINE_RAW_SPINLOCK(i8259A_lock);
static void disable_8259A_irq(struct irq_data *d);
static void enable_8259A_irq(struct irq_data *d);
static void mask_and_ack_8259A(struct irq_data *d);
static void init_8259A(int auto_eoi);

static struct irq_chip i8259A_chip = {
	.name			= "XT-PIC",
	.irq_mask		= disable_8259A_irq,
	.irq_disable		= disable_8259A_irq,
	.irq_unmask		= enable_8259A_irq,
	.irq_mask_ack		= mask_and_ack_8259A,
};

/*
 * 8259A PIC functions to handle ISA devices:
 */

/*
 * This contains the irq mask for both 8259A irq controllers,
 */
static unsigned int cached_irq_mask = 0xffff;

#define cached_master_mask	(cached_irq_mask)
#define cached_slave_mask	(cached_irq_mask >> 8)

static void disable_8259A_irq(struct irq_data *d)
{
	unsigned int mask, irq = d->irq - I8259A_IRQ_BASE;
	unsigned long flags;

	mask = 1 << irq;
	raw_spin_lock_irqsave(&i8259A_lock, flags);
	cached_irq_mask |= mask;
	if (irq & 8)
		outb(cached_slave_mask, PIC_SLAVE_IMR);
	else
		outb(cached_master_mask, PIC_MASTER_IMR);
	raw_spin_unlock_irqrestore(&i8259A_lock, flags);
}

static void enable_8259A_irq(struct irq_data *d)
{
	unsigned int mask, irq = d->irq - I8259A_IRQ_BASE;
	unsigned long flags;

	mask = ~(1 << irq);
	raw_spin_lock_irqsave(&i8259A_lock, flags);
	cached_irq_mask &= mask;
	if (irq & 8)
		outb(cached_slave_mask, PIC_SLAVE_IMR);
	else
		outb(cached_master_mask, PIC_MASTER_IMR);
	raw_spin_unlock_irqrestore(&i8259A_lock, flags);
}

int i8259A_irq_pending(unsigned int irq)
{
	unsigned int mask;
	unsigned long flags;
	int ret;

	irq -= I8259A_IRQ_BASE;
	mask = 1 << irq;
	raw_spin_lock_irqsave(&i8259A_lock, flags);
	if (irq < 8)
		ret = inb(PIC_MASTER_CMD) & mask;
	else
		ret = inb(PIC_SLAVE_CMD) & (mask >> 8);
	raw_spin_unlock_irqrestore(&i8259A_lock, flags);

	return ret;
}

void make_8259A_irq(unsigned int irq)
{
	disable_irq_nosync(irq);
	irq_set_chip_and_handler(irq, &i8259A_chip, handle_level_irq);
	enable_irq(irq);
}

/*
 * This function assumes to be called rarely. Switching between
 * 8259A registers is slow.
 * This has to be protected by the irq controller spinlock
 * before being called.
 */
static inline int i8259A_irq_real(unsigned int irq)
{
	int value;
	int irqmask = 1 << irq;

	if (irq < 8) {
		outb(0x0B, PIC_MASTER_CMD);	/* ISR register */
		value = inb(PIC_MASTER_CMD) & irqmask;
		outb(0x0A, PIC_MASTER_CMD);	/* back to the IRR register */
		return value;
	}
	outb(0x0B, PIC_SLAVE_CMD);	/* ISR register */
	value = inb(PIC_SLAVE_CMD) & (irqmask >> 8);
	outb(0x0A, PIC_SLAVE_CMD);	/* back to the IRR register */
	return value;
}

/*
 * Careful! The 8259A is a fragile beast, it pretty
 * much _has_ to be done exactly like this (mask it
 * first, _then_ send the EOI, and the order of EOI
 * to the two 8259s is important!
 */
static void mask_and_ack_8259A(struct irq_data *d)
{
	unsigned int irqmask, irq = d->irq - I8259A_IRQ_BASE;
	unsigned long flags;

	irqmask = 1 << irq;
	raw_spin_lock_irqsave(&i8259A_lock, flags);
	/*
	 * Lightweight spurious IRQ detection. We do not want
	 * to overdo spurious IRQ handling - it's usually a sign
	 * of hardware problems, so we only do the checks we can
	 * do without slowing down good hardware unnecessarily.
	 *
	 * Note that IRQ7 and IRQ15 (the two spurious IRQs
	 * usually resulting from the 8259A-1|2 PICs) occur
	 * even if the IRQ is masked in the 8259A. Thus we
	 * can check spurious 8259A IRQs without doing the
	 * quite slow i8259A_irq_real() call for every IRQ.
	 * This does not cover 100% of spurious interrupts,
	 * but should be enough to warn the user that there
	 * is something bad going on ...
	 */
	if (cached_irq_mask & irqmask)
		goto spurious_8259A_irq;
	cached_irq_mask |= irqmask;

handle_real_irq:
	if (irq & 8) {
		inb(PIC_SLAVE_IMR);	/* DUMMY - (do we need this?) */
		outb(cached_slave_mask, PIC_SLAVE_IMR);
		outb(0x60+(irq&7), PIC_SLAVE_CMD);/* 'Specific EOI' to slave */
		outb(0x60+PIC_CASCADE_IR, PIC_MASTER_CMD); /* 'Specific EOI' to master-IRQ2 */
	} else {
		inb(PIC_MASTER_IMR);	/* DUMMY - (do we need this?) */
		outb(cached_master_mask, PIC_MASTER_IMR);
		outb(0x60+irq, PIC_MASTER_CMD); /* 'Specific EOI to master */
	}
	raw_spin_unlock_irqrestore(&i8259A_lock, flags);
	return;

spurious_8259A_irq:
	/*
	 * this is the slow path - should happen rarely.
	 */
	if (i8259A_irq_real(irq))
		/*
		 * oops, the IRQ _is_ in service according to the
		 * 8259A - not spurious, go handle it.
		 */
		goto handle_real_irq;

	{
		static int spurious_irq_mask;
		/*
		 * At this point we can be sure the IRQ is spurious,
		 * lets ACK and report it. [once per IRQ]
		 */
		if (!(spurious_irq_mask & irqmask)) {
			printk(KERN_DEBUG "spurious 8259A interrupt: IRQ%d.\n", irq);
			spurious_irq_mask |= irqmask;
		}
		atomic_inc(&irq_err_count);
		/*
		 * Theoretically we do not have to handle this IRQ,
		 * but in Linux this does not cause problems and is
		 * simpler for us.
		 */
		goto handle_real_irq;
	}
}

static void i8259A_resume(void)
{
	if (i8259A_auto_eoi >= 0)
		init_8259A(i8259A_auto_eoi);
}

static void i8259A_shutdown(void)
{
	/* Put the i8259A into a quiescent state that
	 * the kernel initialization code can get it
	 * out of.
	 */
	if (i8259A_auto_eoi >= 0) {
		outb(0xff, PIC_MASTER_IMR);	/* mask all of 8259A-1 */
		outb(0xff, PIC_SLAVE_IMR);	/* mask all of 8259A-2 */
	}
}

static struct syscore_ops i8259_syscore_ops = {
	.resume = i8259A_resume,
	.shutdown = i8259A_shutdown,
};

static int __init i8259A_init_sysfs(void)
{
	register_syscore_ops(&i8259_syscore_ops);
	return 0;
}

device_initcall(i8259A_init_sysfs);

static void init_8259A(int auto_eoi)
{
	unsigned long flags;

	i8259A_auto_eoi = auto_eoi;

	raw_spin_lock_irqsave(&i8259A_lock, flags);

	outb(0xff, PIC_MASTER_IMR);	/* mask all of 8259A-1 */
	outb(0xff, PIC_SLAVE_IMR);	/* mask all of 8259A-2 */

	/*
	 * outb_p - this has to work on a wide range of PC hardware.
	 */
	outb_p(0x11, PIC_MASTER_CMD);	/* ICW1: select 8259A-1 init */
	outb_p(I8259A_IRQ_BASE + 0, PIC_MASTER_IMR);	/* ICW2: 8259A-1 IR0 mapped to I8259A_IRQ_BASE + 0x00 */
	outb_p(1U << PIC_CASCADE_IR, PIC_MASTER_IMR);	/* 8259A-1 (the master) has a slave on IR2 */
	if (auto_eoi)	/* master does Auto EOI */
		outb_p(MASTER_ICW4_DEFAULT | PIC_ICW4_AEOI, PIC_MASTER_IMR);
	else		/* master expects normal EOI */
		outb_p(MASTER_ICW4_DEFAULT, PIC_MASTER_IMR);

	outb_p(0x11, PIC_SLAVE_CMD);	/* ICW1: select 8259A-2 init */
	outb_p(I8259A_IRQ_BASE + 8, PIC_SLAVE_IMR);	/* ICW2: 8259A-2 IR0 mapped to I8259A_IRQ_BASE + 0x08 */
	outb_p(PIC_CASCADE_IR, PIC_SLAVE_IMR);	/* 8259A-2 is a slave on master's IR2 */
	outb_p(SLAVE_ICW4_DEFAULT, PIC_SLAVE_IMR); /* (slave's support for AEOI in flat mode is to be investigated) */
	if (auto_eoi)
		/*
		 * In AEOI mode we just have to mask the interrupt
		 * when acking.
		 */
		i8259A_chip.irq_mask_ack = disable_8259A_irq;
	else
		i8259A_chip.irq_mask_ack = mask_and_ack_8259A;

	udelay(100);		/* wait for 8259A to initialize */

	outb(cached_master_mask, PIC_MASTER_IMR); /* restore master IRQ mask */
	outb(cached_slave_mask, PIC_SLAVE_IMR);	  /* restore slave IRQ mask */

	raw_spin_unlock_irqrestore(&i8259A_lock, flags);
}

/*
 * IRQ2 is cascade interrupt to second interrupt controller
 */
static struct irqaction irq2 = {
	.handler = no_action,
	.name = "cascade",
	.flags = IRQF_NO_THREAD,
};

static struct resource pic1_io_resource = {
	.name = "pic1",
	.start = PIC_MASTER_CMD,
	.end = PIC_MASTER_IMR,
	.flags = IORESOURCE_BUSY
};

static struct resource pic2_io_resource = {
	.name = "pic2",
	.start = PIC_SLAVE_CMD,
	.end = PIC_SLAVE_IMR,
	.flags = IORESOURCE_BUSY
};

static int i8259A_irq_domain_map(struct irq_domain *d, unsigned int virq,
				 irq_hw_number_t hw)
{
	irq_set_chip_and_handler(virq, &i8259A_chip, handle_level_irq);
	irq_set_probe(virq);
	return 0;
}

static struct irq_domain_ops i8259A_ops = {
	.map = i8259A_irq_domain_map,
	.xlate = irq_domain_xlate_onecell,
};

/*
 * On systems with i8259-style interrupt controllers we assume for
 * driver compatibility reasons interrupts 0 - 15 to be the i8259
 * interrupts even if the hardware uses a different interrupt numbering.
 */
void __init init_i8259_irqs(void)
{
	struct irq_domain *domain;

	insert_resource(&ioport_resource, &pic1_io_resource);
	insert_resource(&ioport_resource, &pic2_io_resource);

	init_8259A(0);

	domain = irq_domain_add_legacy(NULL, 16, I8259A_IRQ_BASE, 0,
				       &i8259A_ops, NULL);
	if (!domain)
		panic("Failed to add i8259 IRQ domain");

	setup_irq(I8259A_IRQ_BASE + PIC_CASCADE_IR, &irq2);
}