arch/powerpc/kernel/irq.c - linux - Git at Google

 /*
  *  arch/ppc/kernel/irq.c
  *
  *  Derived from arch/i386/kernel/irq.c
  *    Copyright (C) 1992 Linus Torvalds
  *  Adapted from arch/i386 by Gary Thomas
  *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
  *  Updated and modified by Cort Dougan <cort@fsmlabs.com>
  *    Copyright (C) 1996-2001 Cort Dougan
  *  Adapted for Power Macintosh by Paul Mackerras
  *    Copyright (C) 1996 Paul Mackerras (paulus@cs.anu.edu.au)
  *  Amiga/APUS changes by Jesper Skov (jskov@cygnus.co.uk).
  *
  * 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.
  *
  * This file contains the code used by various IRQ handling routines:
  * asking for different IRQ's should be done through these routines
  * instead of just grabbing them. Thus setups with different IRQ numbers
  * shouldn't result in any weird surprises, and installing new handlers
  * should be easier.
  *
  * The MPC8xx has an interrupt mask in the SIU.  If a bit is set, the
  * interrupt is _enabled_.  As expected, IRQ0 is bit 0 in the 32-bit
  * mask register (of which only 16 are defined), hence the weird shifting
  * and complement of the cached_irq_mask.  I want to be able to stuff
  * this right into the SIU SMASK register.
  * Many of the prep/chrp functions are conditional compiled on CONFIG_8xx
  * to reduce code space and undefined function references.
  */

 #include <linux/module.h>
 #include <linux/threads.h>
 #include <linux/kernel_stat.h>
 #include <linux/signal.h>
 #include <linux/sched.h>
 #include <linux/ptrace.h>
 #include <linux/ioport.h>
 #include <linux/interrupt.h>
 #include <linux/timex.h>
 #include <linux/config.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/delay.h>
 #include <linux/irq.h>
 #include <linux/seq_file.h>
 #include <linux/cpumask.h>
 #include <linux/profile.h>
 #include <linux/bitops.h>

 #include <asm/uaccess.h>
 #include <asm/system.h>
 #include <asm/io.h>
 #include <asm/pgtable.h>
 #include <asm/irq.h>
 #include <asm/cache.h>
 #include <asm/prom.h>
 #include <asm/ptrace.h>
 #include <asm/machdep.h>
 #ifdef CONFIG_PPC_ISERIES
 #include <asm/paca.h>
 #endif

 int __irq_offset_value;
 #ifdef CONFIG_PPC32
 EXPORT_SYMBOL(__irq_offset_value);
 #endif

 static int ppc_spurious_interrupts;

 #ifdef CONFIG_PPC32
 #define NR_MASK_WORDS	((NR_IRQS + 31) / 32)

 unsigned long ppc_cached_irq_mask[NR_MASK_WORDS];
 atomic_t ppc_n_lost_interrupts;

 #ifdef CONFIG_TAU_INT
 extern int tau_initialized;
 extern int tau_interrupts(int);
 #endif

 #if defined(CONFIG_SMP) && !defined(CONFIG_PPC_MERGE)
 extern atomic_t ipi_recv;
 extern atomic_t ipi_sent;
 #endif
 #endif /* CONFIG_PPC32 */

 #ifdef CONFIG_PPC64
 EXPORT_SYMBOL(irq_desc);

 int distribute_irqs = 1;
 u64 ppc64_interrupt_controller;
 #endif /* CONFIG_PPC64 */

 int show_interrupts(struct seq_file *p, void *v)
 {
 	int i = *(loff_t *)v, j;
 	struct irqaction *action;
 	irq_desc_t *desc;
 	unsigned long flags;

 	if (i == 0) {
 		seq_puts(p, "           ");
 		for_each_online_cpu(j)
 			seq_printf(p, "CPU%d       ", j);
 		seq_putc(p, '\n');
 	}

 	if (i < NR_IRQS) {
 		desc = get_irq_desc(i);
 		spin_lock_irqsave(&desc->lock, flags);
 		action = desc->action;
 		if (!action || !action->handler)
 			goto skip;
 		seq_printf(p, "%3d: ", i);
 #ifdef CONFIG_SMP
 		for_each_online_cpu(j)
 			seq_printf(p, "%10u ", kstat_cpu(j).irqs[i]);
 #else
 		seq_printf(p, "%10u ", kstat_irqs(i));
 #endif /* CONFIG_SMP */
 		if (desc->handler)
 			seq_printf(p, " %s ", desc->handler->typename);
 		else
 			seq_puts(p, "  None      ");
 		seq_printf(p, "%s", (desc->status & IRQ_LEVEL) ? "Level " : "Edge  ");
 		seq_printf(p, "    %s", action->name);
 		for (action = action->next; action; action = action->next)
 			seq_printf(p, ", %s", action->name);
 		seq_putc(p, '\n');
 skip:
 		spin_unlock_irqrestore(&desc->lock, flags);
 	} else if (i == NR_IRQS) {
 #ifdef CONFIG_PPC32
 #ifdef CONFIG_TAU_INT
 		if (tau_initialized){
 			seq_puts(p, "TAU: ");
 			for (j = 0; j < NR_CPUS; j++)
 				if (cpu_online(j))
 					seq_printf(p, "%10u ", tau_interrupts(j));
 			seq_puts(p, "  PowerPC             Thermal Assist (cpu temp)\n");
 		}
 #endif
 #if defined(CONFIG_SMP) && !defined(CONFIG_PPC_MERGE)
 		/* should this be per processor send/receive? */
 		seq_printf(p, "IPI (recv/sent): %10u/%u\n",
 				atomic_read(&ipi_recv), atomic_read(&ipi_sent));
 #endif
 #endif /* CONFIG_PPC32 */
 		seq_printf(p, "BAD: %10u\n", ppc_spurious_interrupts);
 	}
 	return 0;
 }

 #ifdef CONFIG_HOTPLUG_CPU
 void fixup_irqs(cpumask_t map)
 {
 	unsigned int irq;
 	static int warned;

 	for_each_irq(irq) {
 		cpumask_t mask;

 		if (irq_desc[irq].status & IRQ_PER_CPU)
 			continue;

 		cpus_and(mask, irq_affinity[irq], map);
 		if (any_online_cpu(mask) == NR_CPUS) {
 			printk("Breaking affinity for irq %i\n", irq);
 			mask = map;
 		}
 		if (irq_desc[irq].handler->set_affinity)
 			irq_desc[irq].handler->set_affinity(irq, mask);
 		else if (irq_desc[irq].action && !(warned++))
 			printk("Cannot set affinity for irq %i\n", irq);
 	}

 	local_irq_enable();
 	mdelay(1);
 	local_irq_disable();
 }
 #endif

 void do_IRQ(struct pt_regs *regs)
 {
 	int irq;
 #ifdef CONFIG_IRQSTACKS
 	struct thread_info *curtp, *irqtp;
 #endif

         irq_enter();

 #ifdef CONFIG_DEBUG_STACKOVERFLOW
 	/* Debugging check for stack overflow: is there less than 2KB free? */
 	{
 		long sp;

 		sp = __get_SP() & (THREAD_SIZE-1);

 		if (unlikely(sp < (sizeof(struct thread_info) + 2048))) {
 			printk("do_IRQ: stack overflow: %ld\n",
 				sp - sizeof(struct thread_info));
 			dump_stack();
 		}
 	}
 #endif

 	/*
 	 * Every platform is required to implement ppc_md.get_irq.
 	 * This function will either return an irq number or -1 to
 	 * indicate there are no more pending.
 	 * The value -2 is for buggy hardware and means that this IRQ
 	 * has already been handled. -- Tom
 	 */
 	irq = ppc_md.get_irq(regs);

 	if (irq >= 0) {
 #ifdef CONFIG_IRQSTACKS
 		/* Switch to the irq stack to handle this */
 		curtp = current_thread_info();
 		irqtp = hardirq_ctx[smp_processor_id()];
 		if (curtp != irqtp) {
 			irqtp->task = curtp->task;
 			irqtp->flags = 0;
 			call___do_IRQ(irq, regs, irqtp);
 			irqtp->task = NULL;
 			if (irqtp->flags)
 				set_bits(irqtp->flags, &curtp->flags);
 		} else
 #endif
 			__do_IRQ(irq, regs);
 	} else if (irq != -2)
 		/* That's not SMP safe ... but who cares ? */
 		ppc_spurious_interrupts++;

         irq_exit();

 #ifdef CONFIG_PPC_ISERIES
 	if (get_lppaca()->int_dword.fields.decr_int) {
 		get_lppaca()->int_dword.fields.decr_int = 0;
 		/* Signal a fake decrementer interrupt */
 		timer_interrupt(regs);
 	}
 #endif
 }

 void __init init_IRQ(void)
 {
 #ifdef CONFIG_PPC64
 	static int once = 0;

 	if (once)
 		return;

 	once++;

 #endif
 	ppc_md.init_IRQ();
 #ifdef CONFIG_PPC64
 	irq_ctx_init();
 #endif
 }

 #ifdef CONFIG_PPC64
 /*
  * Virtual IRQ mapping code, used on systems with XICS interrupt controllers.
  */

 #define UNDEFINED_IRQ 0xffffffff
 unsigned int virt_irq_to_real_map[NR_IRQS];

 /*
  * Don't use virtual irqs 0, 1, 2 for devices.
  * The pcnet32 driver considers interrupt numbers < 2 to be invalid,
  * and 2 is the XICS IPI interrupt.
  * We limit virtual irqs to 17 less than NR_IRQS so that when we
  * offset them by 16 (to reserve the first 16 for ISA interrupts)
  * we don't end up with an interrupt number >= NR_IRQS.
  */
 #define MIN_VIRT_IRQ	3
 #define MAX_VIRT_IRQ	(NR_IRQS - NUM_ISA_INTERRUPTS - 1)
 #define NR_VIRT_IRQS	(MAX_VIRT_IRQ - MIN_VIRT_IRQ + 1)

 void
 virt_irq_init(void)
 {
 	int i;
 	for (i = 0; i < NR_IRQS; i++)
 		virt_irq_to_real_map[i] = UNDEFINED_IRQ;
 }

 /* Create a mapping for a real_irq if it doesn't already exist.
  * Return the virtual irq as a convenience.
  */
 int virt_irq_create_mapping(unsigned int real_irq)
 {
 	unsigned int virq, first_virq;
 	static int warned;

 	if (ppc64_interrupt_controller == IC_OPEN_PIC)
 		return real_irq;	/* no mapping for openpic (for now) */

 	if (ppc64_interrupt_controller == IC_CELL_PIC)
 		return real_irq;	/* no mapping for iic either */

 	/* don't map interrupts < MIN_VIRT_IRQ */
 	if (real_irq < MIN_VIRT_IRQ) {
 		virt_irq_to_real_map[real_irq] = real_irq;
 		return real_irq;
 	}

 	/* map to a number between MIN_VIRT_IRQ and MAX_VIRT_IRQ */
 	virq = real_irq;
 	if (virq > MAX_VIRT_IRQ)
 		virq = (virq % NR_VIRT_IRQS) + MIN_VIRT_IRQ;

 	/* search for this number or a free slot */
 	first_virq = virq;
 	while (virt_irq_to_real_map[virq] != UNDEFINED_IRQ) {
 		if (virt_irq_to_real_map[virq] == real_irq)
 			return virq;
 		if (++virq > MAX_VIRT_IRQ)
 			virq = MIN_VIRT_IRQ;
 		if (virq == first_virq)
 			goto nospace;	/* oops, no free slots */
 	}

 	virt_irq_to_real_map[virq] = real_irq;
 	return virq;

  nospace:
 	if (!warned) {
 		printk(KERN_CRIT "Interrupt table is full\n");
 		printk(KERN_CRIT "Increase NR_IRQS (currently %d) "
 		       "in your kernel sources and rebuild.\n", NR_IRQS);
 		warned = 1;
 	}
 	return NO_IRQ;
 }

 /*
  * In most cases will get a hit on the very first slot checked in the
  * virt_irq_to_real_map.  Only when there are a large number of
  * IRQs will this be expensive.
  */
 unsigned int real_irq_to_virt_slowpath(unsigned int real_irq)
 {
 	unsigned int virq;
 	unsigned int first_virq;

 	virq = real_irq;

 	if (virq > MAX_VIRT_IRQ)
 		virq = (virq % NR_VIRT_IRQS) + MIN_VIRT_IRQ;

 	first_virq = virq;

 	do {
 		if (virt_irq_to_real_map[virq] == real_irq)
 			return virq;

 		virq++;

 		if (virq >= MAX_VIRT_IRQ)
 			virq = 0;

 	} while (first_virq != virq);

 	return NO_IRQ;

 }

 #ifdef CONFIG_IRQSTACKS
 struct thread_info *softirq_ctx[NR_CPUS];
 struct thread_info *hardirq_ctx[NR_CPUS];

 void irq_ctx_init(void)
 {
 	struct thread_info *tp;
 	int i;

 	for_each_cpu(i) {
 		memset((void *)softirq_ctx[i], 0, THREAD_SIZE);
 		tp = softirq_ctx[i];
 		tp->cpu = i;
 		tp->preempt_count = SOFTIRQ_OFFSET;

 		memset((void *)hardirq_ctx[i], 0, THREAD_SIZE);
 		tp = hardirq_ctx[i];
 		tp->cpu = i;
 		tp->preempt_count = HARDIRQ_OFFSET;
 	}
 }

 void do_softirq(void)
 {
 	unsigned long flags;
 	struct thread_info *curtp, *irqtp;

 	if (in_interrupt())
 		return;

 	local_irq_save(flags);

 	if (local_softirq_pending()) {
 		curtp = current_thread_info();
 		irqtp = softirq_ctx[smp_processor_id()];
 		irqtp->task = curtp->task;
 		call_do_softirq(irqtp);
 		irqtp->task = NULL;
 	}

 	local_irq_restore(flags);
 }
 EXPORT_SYMBOL(do_softirq);

 #endif /* CONFIG_IRQSTACKS */

 static int __init setup_noirqdistrib(char *str)
 {
 	distribute_irqs = 0;
 	return 1;
 }

 __setup("noirqdistrib", setup_noirqdistrib);
 #endif /* CONFIG_PPC64 */
	/*
	* arch/ppc/kernel/irq.c
	*
	* Derived from arch/i386/kernel/irq.c
	* Copyright (C) 1992 Linus Torvalds
	* Adapted from arch/i386 by Gary Thomas
	* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
	* Updated and modified by Cort Dougan <cort@fsmlabs.com>
	* Copyright (C) 1996-2001 Cort Dougan
	* Adapted for Power Macintosh by Paul Mackerras
	* Copyright (C) 1996 Paul Mackerras (paulus@cs.anu.edu.au)
	* Amiga/APUS changes by Jesper Skov (jskov@cygnus.co.uk).
	*
	* 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.
	*
	* This file contains the code used by various IRQ handling routines:
	* asking for different IRQ's should be done through these routines
	* instead of just grabbing them. Thus setups with different IRQ numbers
	* shouldn't result in any weird surprises, and installing new handlers
	* should be easier.
	*
	* The MPC8xx has an interrupt mask in the SIU. If a bit is set, the
	* interrupt is _enabled_. As expected, IRQ0 is bit 0 in the 32-bit
	* mask register (of which only 16 are defined), hence the weird shifting
	* and complement of the cached_irq_mask. I want to be able to stuff
	* this right into the SIU SMASK register.
	* Many of the prep/chrp functions are conditional compiled on CONFIG_8xx
	* to reduce code space and undefined function references.
	*/

	#include <linux/module.h>
	#include <linux/threads.h>
	#include <linux/kernel_stat.h>
	#include <linux/signal.h>
	#include <linux/sched.h>
	#include <linux/ptrace.h>
	#include <linux/ioport.h>
	#include <linux/interrupt.h>
	#include <linux/timex.h>
	#include <linux/config.h>
	#include <linux/init.h>
	#include <linux/slab.h>
	#include <linux/delay.h>
	#include <linux/irq.h>
	#include <linux/seq_file.h>
	#include <linux/cpumask.h>
	#include <linux/profile.h>
	#include <linux/bitops.h>

	#include <asm/uaccess.h>
	#include <asm/system.h>
	#include <asm/io.h>
	#include <asm/pgtable.h>
	#include <asm/irq.h>
	#include <asm/cache.h>
	#include <asm/prom.h>
	#include <asm/ptrace.h>
	#include <asm/machdep.h>
	#ifdef CONFIG_PPC_ISERIES
	#include <asm/paca.h>
	#endif

	int __irq_offset_value;
	#ifdef CONFIG_PPC32
	EXPORT_SYMBOL(__irq_offset_value);
	#endif

	static int ppc_spurious_interrupts;

	#ifdef CONFIG_PPC32
	#define NR_MASK_WORDS ((NR_IRQS + 31) / 32)

	unsigned long ppc_cached_irq_mask[NR_MASK_WORDS];
	atomic_t ppc_n_lost_interrupts;

	#ifdef CONFIG_TAU_INT
	extern int tau_initialized;
	extern int tau_interrupts(int);
	#endif

	#if defined(CONFIG_SMP) && !defined(CONFIG_PPC_MERGE)
	extern atomic_t ipi_recv;
	extern atomic_t ipi_sent;
	#endif
	#endif /* CONFIG_PPC32 */

	#ifdef CONFIG_PPC64
	EXPORT_SYMBOL(irq_desc);

	int distribute_irqs = 1;
	u64 ppc64_interrupt_controller;
	#endif /* CONFIG_PPC64 */

	int show_interrupts(struct seq_file p, void v)
	{
	int i = (loff_t )v, j;
	struct irqaction *action;
	irq_desc_t *desc;
	unsigned long flags;

	if (i == 0) {
	seq_puts(p, " ");
	for_each_online_cpu(j)
	seq_printf(p, "CPU%d ", j);
	seq_putc(p, '\n');
	}

	if (i < NR_IRQS) {
	desc = get_irq_desc(i);
	spin_lock_irqsave(&desc->lock, flags);
	action = desc->action;
	if (!action \|\| !action->handler)
	goto skip;
	seq_printf(p, "%3d: ", i);
	#ifdef CONFIG_SMP
	for_each_online_cpu(j)
	seq_printf(p, "%10u ", kstat_cpu(j).irqs[i]);
	#else
	seq_printf(p, "%10u ", kstat_irqs(i));
	#endif /* CONFIG_SMP */
	if (desc->handler)
	seq_printf(p, " %s ", desc->handler->typename);
	else
	seq_puts(p, " None ");
	seq_printf(p, "%s", (desc->status & IRQ_LEVEL) ? "Level " : "Edge ");
	seq_printf(p, " %s", action->name);
	for (action = action->next; action; action = action->next)
	seq_printf(p, ", %s", action->name);
	seq_putc(p, '\n');
	skip:
	spin_unlock_irqrestore(&desc->lock, flags);
	} else if (i == NR_IRQS) {
	#ifdef CONFIG_PPC32
	#ifdef CONFIG_TAU_INT
	if (tau_initialized){
	seq_puts(p, "TAU: ");
	for (j = 0; j < NR_CPUS; j++)
	if (cpu_online(j))
	seq_printf(p, "%10u ", tau_interrupts(j));
	seq_puts(p, " PowerPC Thermal Assist (cpu temp)\n");
	}
	#endif
	#if defined(CONFIG_SMP) && !defined(CONFIG_PPC_MERGE)
	/* should this be per processor send/receive? */
	seq_printf(p, "IPI (recv/sent): %10u/%u\n",
	atomic_read(&ipi_recv), atomic_read(&ipi_sent));
	#endif
	#endif /* CONFIG_PPC32 */
	seq_printf(p, "BAD: %10u\n", ppc_spurious_interrupts);
	}
	return 0;
	}

	#ifdef CONFIG_HOTPLUG_CPU
	void fixup_irqs(cpumask_t map)
	{
	unsigned int irq;
	static int warned;

	for_each_irq(irq) {
	cpumask_t mask;

	if (irq_desc[irq].status & IRQ_PER_CPU)
	continue;

	cpus_and(mask, irq_affinity[irq], map);
	if (any_online_cpu(mask) == NR_CPUS) {
	printk("Breaking affinity for irq %i\n", irq);
	mask = map;
	}
	if (irq_desc[irq].handler->set_affinity)
	irq_desc[irq].handler->set_affinity(irq, mask);
	else if (irq_desc[irq].action && !(warned++))
	printk("Cannot set affinity for irq %i\n", irq);
	}

	local_irq_enable();
	mdelay(1);
	local_irq_disable();
	}
	#endif

	void do_IRQ(struct pt_regs *regs)
	{
	int irq;
	#ifdef CONFIG_IRQSTACKS
	struct thread_info curtp, irqtp;
	#endif

	irq_enter();

	#ifdef CONFIG_DEBUG_STACKOVERFLOW
	/* Debugging check for stack overflow: is there less than 2KB free? */
	{
	long sp;

	sp = __get_SP() & (THREAD_SIZE-1);

	if (unlikely(sp < (sizeof(struct thread_info) + 2048))) {
	printk("do_IRQ: stack overflow: %ld\n",
	sp - sizeof(struct thread_info));
	dump_stack();
	}
	}
	#endif

	/*
	* Every platform is required to implement ppc_md.get_irq.
	* This function will either return an irq number or -1 to
	* indicate there are no more pending.
	* The value -2 is for buggy hardware and means that this IRQ
	* has already been handled. -- Tom
	*/
	irq = ppc_md.get_irq(regs);

	if (irq >= 0) {
	#ifdef CONFIG_IRQSTACKS
	/* Switch to the irq stack to handle this */
	curtp = current_thread_info();
	irqtp = hardirq_ctx[smp_processor_id()];
	if (curtp != irqtp) {
	irqtp->task = curtp->task;
	irqtp->flags = 0;
	call___do_IRQ(irq, regs, irqtp);
	irqtp->task = NULL;
	if (irqtp->flags)
	set_bits(irqtp->flags, &curtp->flags);
	} else
	#endif
	__do_IRQ(irq, regs);
	} else if (irq != -2)
	/* That's not SMP safe ... but who cares ? */
	ppc_spurious_interrupts++;

	irq_exit();

	#ifdef CONFIG_PPC_ISERIES
	if (get_lppaca()->int_dword.fields.decr_int) {
	get_lppaca()->int_dword.fields.decr_int = 0;
	/* Signal a fake decrementer interrupt */
	timer_interrupt(regs);
	}
	#endif
	}

	void __init init_IRQ(void)
	{
	#ifdef CONFIG_PPC64
	static int once = 0;

	if (once)
	return;

	once++;

	#endif
	ppc_md.init_IRQ();
	#ifdef CONFIG_PPC64
	irq_ctx_init();
	#endif
	}

	#ifdef CONFIG_PPC64
	/*
	* Virtual IRQ mapping code, used on systems with XICS interrupt controllers.
	*/

	#define UNDEFINED_IRQ 0xffffffff
	unsigned int virt_irq_to_real_map[NR_IRQS];

	/*
	* Don't use virtual irqs 0, 1, 2 for devices.
	* The pcnet32 driver considers interrupt numbers < 2 to be invalid,
	* and 2 is the XICS IPI interrupt.
	* We limit virtual irqs to 17 less than NR_IRQS so that when we
	* offset them by 16 (to reserve the first 16 for ISA interrupts)
	* we don't end up with an interrupt number >= NR_IRQS.
	*/
	#define MIN_VIRT_IRQ 3
	#define MAX_VIRT_IRQ (NR_IRQS - NUM_ISA_INTERRUPTS - 1)
	#define NR_VIRT_IRQS (MAX_VIRT_IRQ - MIN_VIRT_IRQ + 1)

	void
	virt_irq_init(void)
	{
	int i;
	for (i = 0; i < NR_IRQS; i++)
	virt_irq_to_real_map[i] = UNDEFINED_IRQ;
	}

	/* Create a mapping for a real_irq if it doesn't already exist.
	* Return the virtual irq as a convenience.
	*/
	int virt_irq_create_mapping(unsigned int real_irq)
	{
	unsigned int virq, first_virq;
	static int warned;

	if (ppc64_interrupt_controller == IC_OPEN_PIC)
	return real_irq; /* no mapping for openpic (for now) */

	if (ppc64_interrupt_controller == IC_CELL_PIC)
	return real_irq; /* no mapping for iic either */

	/* don't map interrupts < MIN_VIRT_IRQ */
	if (real_irq < MIN_VIRT_IRQ) {
	virt_irq_to_real_map[real_irq] = real_irq;
	return real_irq;
	}

	/* map to a number between MIN_VIRT_IRQ and MAX_VIRT_IRQ */
	virq = real_irq;
	if (virq > MAX_VIRT_IRQ)
	virq = (virq % NR_VIRT_IRQS) + MIN_VIRT_IRQ;

	/* search for this number or a free slot */
	first_virq = virq;
	while (virt_irq_to_real_map[virq] != UNDEFINED_IRQ) {
	if (virt_irq_to_real_map[virq] == real_irq)
	return virq;
	if (++virq > MAX_VIRT_IRQ)
	virq = MIN_VIRT_IRQ;
	if (virq == first_virq)
	goto nospace; /* oops, no free slots */
	}

	virt_irq_to_real_map[virq] = real_irq;
	return virq;

	nospace:
	if (!warned) {
	printk(KERN_CRIT "Interrupt table is full\n");
	printk(KERN_CRIT "Increase NR_IRQS (currently %d) "
	"in your kernel sources and rebuild.\n", NR_IRQS);
	warned = 1;
	}
	return NO_IRQ;
	}

	/*
	* In most cases will get a hit on the very first slot checked in the
	* virt_irq_to_real_map. Only when there are a large number of
	* IRQs will this be expensive.
	*/
	unsigned int real_irq_to_virt_slowpath(unsigned int real_irq)
	{
	unsigned int virq;
	unsigned int first_virq;

	virq = real_irq;

	if (virq > MAX_VIRT_IRQ)
	virq = (virq % NR_VIRT_IRQS) + MIN_VIRT_IRQ;

	first_virq = virq;

	do {
	if (virt_irq_to_real_map[virq] == real_irq)
	return virq;

	virq++;

	if (virq >= MAX_VIRT_IRQ)
	virq = 0;

	} while (first_virq != virq);

	return NO_IRQ;

	}

	#ifdef CONFIG_IRQSTACKS
	struct thread_info *softirq_ctx[NR_CPUS];
	struct thread_info *hardirq_ctx[NR_CPUS];

	void irq_ctx_init(void)
	{
	struct thread_info *tp;
	int i;

	for_each_cpu(i) {
	memset((void *)softirq_ctx[i], 0, THREAD_SIZE);
	tp = softirq_ctx[i];
	tp->cpu = i;
	tp->preempt_count = SOFTIRQ_OFFSET;

	memset((void *)hardirq_ctx[i], 0, THREAD_SIZE);
	tp = hardirq_ctx[i];
	tp->cpu = i;
	tp->preempt_count = HARDIRQ_OFFSET;
	}
	}

	void do_softirq(void)
	{
	unsigned long flags;
	struct thread_info curtp, irqtp;

	if (in_interrupt())
	return;

	local_irq_save(flags);

	if (local_softirq_pending()) {
	curtp = current_thread_info();
	irqtp = softirq_ctx[smp_processor_id()];
	irqtp->task = curtp->task;
	call_do_softirq(irqtp);
	irqtp->task = NULL;
	}

	local_irq_restore(flags);
	}
	EXPORT_SYMBOL(do_softirq);

	#endif /* CONFIG_IRQSTACKS */

	static int __init setup_noirqdistrib(char *str)
	{
	distribute_irqs = 0;
	return 1;
	}

	__setup("noirqdistrib", setup_noirqdistrib);
	#endif /* CONFIG_PPC64 */