arch/s390/kernel/irq.c - linux/torvalds/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  *    Copyright IBM Corp. 2004, 2011
  *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
  *		 Holger Smolinski <Holger.Smolinski@de.ibm.com>,
  *		 Thomas Spatzier <tspat@de.ibm.com>,
  *
  * This file contains interrupt related functions.
  */

 #include <linux/kernel_stat.h>
 #include <linux/interrupt.h>
 #include <linux/seq_file.h>
 #include <linux/proc_fs.h>
 #include <linux/profile.h>
 #include <linux/export.h>
 #include <linux/kernel.h>
 #include <linux/ftrace.h>
 #include <linux/errno.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/cpu.h>
 #include <linux/irq.h>
 #include <asm/irq_regs.h>
 #include <asm/cputime.h>
 #include <asm/lowcore.h>
 #include <asm/irq.h>
 #include <asm/hw_irq.h>
 #include <asm/stacktrace.h>
 #include "entry.h"

 DEFINE_PER_CPU_SHARED_ALIGNED(struct irq_stat, irq_stat);
 EXPORT_PER_CPU_SYMBOL_GPL(irq_stat);

 struct irq_class {
 	int irq;
 	char *name;
 	char *desc;
 };

 /*
  * The list of "main" irq classes on s390. This is the list of interrupts
  * that appear both in /proc/stat ("intr" line) and /proc/interrupts.
  * Historically only external and I/O interrupts have been part of /proc/stat.
  * We can't add the split external and I/O sub classes since the first field
  * in the "intr" line in /proc/stat is supposed to be the sum of all other
  * fields.
  * Since the external and I/O interrupt fields are already sums we would end
  * up with having a sum which accounts each interrupt twice.
  */
 static const struct irq_class irqclass_main_desc[NR_IRQS_BASE] = {
 	{.irq = EXT_INTERRUPT,	.name = "EXT"},
 	{.irq = IO_INTERRUPT,	.name = "I/O"},
 	{.irq = THIN_INTERRUPT, .name = "AIO"},
 };

 /*
  * The list of split external and I/O interrupts that appear only in
  * /proc/interrupts.
  * In addition this list contains non external / I/O events like NMIs.
  */
 static const struct irq_class irqclass_sub_desc[] = {
 	{.irq = IRQEXT_CLK, .name = "CLK", .desc = "[EXT] Clock Comparator"},
 	{.irq = IRQEXT_EXC, .name = "EXC", .desc = "[EXT] External Call"},
 	{.irq = IRQEXT_EMS, .name = "EMS", .desc = "[EXT] Emergency Signal"},
 	{.irq = IRQEXT_TMR, .name = "TMR", .desc = "[EXT] CPU Timer"},
 	{.irq = IRQEXT_TLA, .name = "TAL", .desc = "[EXT] Timing Alert"},
 	{.irq = IRQEXT_PFL, .name = "PFL", .desc = "[EXT] Pseudo Page Fault"},
 	{.irq = IRQEXT_DSD, .name = "DSD", .desc = "[EXT] DASD Diag"},
 	{.irq = IRQEXT_VRT, .name = "VRT", .desc = "[EXT] Virtio"},
 	{.irq = IRQEXT_SCP, .name = "SCP", .desc = "[EXT] Service Call"},
 	{.irq = IRQEXT_IUC, .name = "IUC", .desc = "[EXT] IUCV"},
 	{.irq = IRQEXT_CMS, .name = "CMS", .desc = "[EXT] CPU-Measurement: Sampling"},
 	{.irq = IRQEXT_CMC, .name = "CMC", .desc = "[EXT] CPU-Measurement: Counter"},
 	{.irq = IRQEXT_FTP, .name = "FTP", .desc = "[EXT] HMC FTP Service"},
 	{.irq = IRQIO_CIO,  .name = "CIO", .desc = "[I/O] Common I/O Layer Interrupt"},
 	{.irq = IRQIO_DAS,  .name = "DAS", .desc = "[I/O] DASD"},
 	{.irq = IRQIO_C15,  .name = "C15", .desc = "[I/O] 3215"},
 	{.irq = IRQIO_C70,  .name = "C70", .desc = "[I/O] 3270"},
 	{.irq = IRQIO_TAP,  .name = "TAP", .desc = "[I/O] Tape"},
 	{.irq = IRQIO_VMR,  .name = "VMR", .desc = "[I/O] Unit Record Devices"},
 	{.irq = IRQIO_LCS,  .name = "LCS", .desc = "[I/O] LCS"},
 	{.irq = IRQIO_CTC,  .name = "CTC", .desc = "[I/O] CTC"},
 	{.irq = IRQIO_ADM,  .name = "ADM", .desc = "[I/O] EADM Subchannel"},
 	{.irq = IRQIO_CSC,  .name = "CSC", .desc = "[I/O] CHSC Subchannel"},
 	{.irq = IRQIO_VIR,  .name = "VIR", .desc = "[I/O] Virtual I/O Devices"},
 	{.irq = IRQIO_QAI,  .name = "QAI", .desc = "[AIO] QDIO Adapter Interrupt"},
 	{.irq = IRQIO_APB,  .name = "APB", .desc = "[AIO] AP Bus"},
 	{.irq = IRQIO_PCF,  .name = "PCF", .desc = "[AIO] PCI Floating Interrupt"},
 	{.irq = IRQIO_PCD,  .name = "PCD", .desc = "[AIO] PCI Directed Interrupt"},
 	{.irq = IRQIO_MSI,  .name = "MSI", .desc = "[AIO] MSI Interrupt"},
 	{.irq = IRQIO_VAI,  .name = "VAI", .desc = "[AIO] Virtual I/O Devices AI"},
 	{.irq = IRQIO_GAL,  .name = "GAL", .desc = "[AIO] GIB Alert"},
 	{.irq = NMI_NMI,    .name = "NMI", .desc = "[NMI] Machine Check"},
 	{.irq = CPU_RST,    .name = "RST", .desc = "[CPU] CPU Restart"},
 };

 void __init init_IRQ(void)
 {
 	BUILD_BUG_ON(ARRAY_SIZE(irqclass_sub_desc) != NR_ARCH_IRQS);
 	init_cio_interrupts();
 	init_airq_interrupts();
 	init_ext_interrupts();
 }

 void do_IRQ(struct pt_regs *regs, int irq)
 {
 	struct pt_regs *old_regs;

 	old_regs = set_irq_regs(regs);
 	irq_enter();
 	if (tod_after_eq(S390_lowcore.int_clock,
 			 S390_lowcore.clock_comparator))
 		/* Serve timer interrupts first. */
 		clock_comparator_work();
 	generic_handle_irq(irq);
 	irq_exit();
 	set_irq_regs(old_regs);
 }

 static void show_msi_interrupt(struct seq_file *p, int irq)
 {
 	struct irq_desc *desc;
 	unsigned long flags;
 	int cpu;

 	irq_lock_sparse();
 	desc = irq_to_desc(irq);
 	if (!desc)
 		goto out;

 	raw_spin_lock_irqsave(&desc->lock, flags);
 	seq_printf(p, "%3d: ", irq);
 	for_each_online_cpu(cpu)
 		seq_printf(p, "%10u ", kstat_irqs_cpu(irq, cpu));

 	if (desc->irq_data.chip)
 		seq_printf(p, " %8s", desc->irq_data.chip->name);

 	if (desc->action)
 		seq_printf(p, "  %s", desc->action->name);

 	seq_putc(p, '\n');
 	raw_spin_unlock_irqrestore(&desc->lock, flags);
 out:
 	irq_unlock_sparse();
 }

 /*
  * show_interrupts is needed by /proc/interrupts.
  */
 int show_interrupts(struct seq_file *p, void *v)
 {
 	int index = *(loff_t *) v;
 	int cpu, irq;

 	get_online_cpus();
 	if (index == 0) {
 		seq_puts(p, "           ");
 		for_each_online_cpu(cpu)
 			seq_printf(p, "CPU%-8d", cpu);
 		seq_putc(p, '\n');
 	}
 	if (index < NR_IRQS_BASE) {
 		seq_printf(p, "%s: ", irqclass_main_desc[index].name);
 		irq = irqclass_main_desc[index].irq;
 		for_each_online_cpu(cpu)
 			seq_printf(p, "%10u ", kstat_irqs_cpu(irq, cpu));
 		seq_putc(p, '\n');
 		goto out;
 	}
 	if (index < nr_irqs) {
 		show_msi_interrupt(p, index);
 		goto out;
 	}
 	for (index = 0; index < NR_ARCH_IRQS; index++) {
 		seq_printf(p, "%s: ", irqclass_sub_desc[index].name);
 		irq = irqclass_sub_desc[index].irq;
 		for_each_online_cpu(cpu)
 			seq_printf(p, "%10u ",
 				   per_cpu(irq_stat, cpu).irqs[irq]);
 		if (irqclass_sub_desc[index].desc)
 			seq_printf(p, "  %s", irqclass_sub_desc[index].desc);
 		seq_putc(p, '\n');
 	}
 out:
 	put_online_cpus();
 	return 0;
 }

 unsigned int arch_dynirq_lower_bound(unsigned int from)
 {
 	return from < NR_IRQS_BASE ? NR_IRQS_BASE : from;
 }

 /*
  * Switch to the asynchronous interrupt stack for softirq execution.
  */
 void do_softirq_own_stack(void)
 {
 	unsigned long old, new;

 	old = current_stack_pointer();
 	/* Check against async. stack address range. */
 	new = S390_lowcore.async_stack;
 	if (((new - old) >> (PAGE_SHIFT + THREAD_SIZE_ORDER)) != 0) {
 		CALL_ON_STACK(__do_softirq, new, 0);
 	} else {
 		/* We are already on the async stack. */
 		__do_softirq();
 	}
 }

 /*
  * ext_int_hash[index] is the list head for all external interrupts that hash
  * to this index.
  */
 static struct hlist_head ext_int_hash[32] ____cacheline_aligned;

 struct ext_int_info {
 	ext_int_handler_t handler;
 	struct hlist_node entry;
 	struct rcu_head rcu;
 	u16 code;
 };

 /* ext_int_hash_lock protects the handler lists for external interrupts */
 static DEFINE_SPINLOCK(ext_int_hash_lock);

 static inline int ext_hash(u16 code)
 {
 	BUILD_BUG_ON(!is_power_of_2(ARRAY_SIZE(ext_int_hash)));

 	return (code + (code >> 9)) & (ARRAY_SIZE(ext_int_hash) - 1);
 }

 int register_external_irq(u16 code, ext_int_handler_t handler)
 {
 	struct ext_int_info *p;
 	unsigned long flags;
 	int index;

 	p = kmalloc(sizeof(*p), GFP_ATOMIC);
 	if (!p)
 		return -ENOMEM;
 	p->code = code;
 	p->handler = handler;
 	index = ext_hash(code);

 	spin_lock_irqsave(&ext_int_hash_lock, flags);
 	hlist_add_head_rcu(&p->entry, &ext_int_hash[index]);
 	spin_unlock_irqrestore(&ext_int_hash_lock, flags);
 	return 0;
 }
 EXPORT_SYMBOL(register_external_irq);

 int unregister_external_irq(u16 code, ext_int_handler_t handler)
 {
 	struct ext_int_info *p;
 	unsigned long flags;
 	int index = ext_hash(code);

 	spin_lock_irqsave(&ext_int_hash_lock, flags);
 	hlist_for_each_entry_rcu(p, &ext_int_hash[index], entry) {
 		if (p->code == code && p->handler == handler) {
 			hlist_del_rcu(&p->entry);
 			kfree_rcu(p, rcu);
 		}
 	}
 	spin_unlock_irqrestore(&ext_int_hash_lock, flags);
 	return 0;
 }
 EXPORT_SYMBOL(unregister_external_irq);

 static irqreturn_t do_ext_interrupt(int irq, void *dummy)
 {
 	struct pt_regs *regs = get_irq_regs();
 	struct ext_code ext_code;
 	struct ext_int_info *p;
 	int index;

 	ext_code = *(struct ext_code *) &regs->int_code;
 	if (ext_code.code != EXT_IRQ_CLK_COMP)
 		set_cpu_flag(CIF_NOHZ_DELAY);

 	index = ext_hash(ext_code.code);
 	rcu_read_lock();
 	hlist_for_each_entry_rcu(p, &ext_int_hash[index], entry) {
 		if (unlikely(p->code != ext_code.code))
 			continue;
 		p->handler(ext_code, regs->int_parm, regs->int_parm_long);
 	}
 	rcu_read_unlock();
 	return IRQ_HANDLED;
 }

 static struct irqaction external_interrupt = {
 	.name	 = "EXT",
 	.handler = do_ext_interrupt,
 };

 void __init init_ext_interrupts(void)
 {
 	int idx;

 	for (idx = 0; idx < ARRAY_SIZE(ext_int_hash); idx++)
 		INIT_HLIST_HEAD(&ext_int_hash[idx]);

 	irq_set_chip_and_handler(EXT_INTERRUPT,
 				 &dummy_irq_chip, handle_percpu_irq);
 	setup_irq(EXT_INTERRUPT, &external_interrupt);
 }

 static DEFINE_SPINLOCK(irq_subclass_lock);
 static unsigned char irq_subclass_refcount[64];

 void irq_subclass_register(enum irq_subclass subclass)
 {
 	spin_lock(&irq_subclass_lock);
 	if (!irq_subclass_refcount[subclass])
 		ctl_set_bit(0, subclass);
 	irq_subclass_refcount[subclass]++;
 	spin_unlock(&irq_subclass_lock);
 }
 EXPORT_SYMBOL(irq_subclass_register);

 void irq_subclass_unregister(enum irq_subclass subclass)
 {
 	spin_lock(&irq_subclass_lock);
 	irq_subclass_refcount[subclass]--;
 	if (!irq_subclass_refcount[subclass])
 		ctl_clear_bit(0, subclass);
 	spin_unlock(&irq_subclass_lock);
 }
 EXPORT_SYMBOL(irq_subclass_unregister);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Copyright IBM Corp. 2004, 2011
	* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>,
	* Holger Smolinski <Holger.Smolinski@de.ibm.com>,
	* Thomas Spatzier <tspat@de.ibm.com>,
	*
	* This file contains interrupt related functions.
	*/

	#include <linux/kernel_stat.h>
	#include <linux/interrupt.h>
	#include <linux/seq_file.h>
	#include <linux/proc_fs.h>
	#include <linux/profile.h>
	#include <linux/export.h>
	#include <linux/kernel.h>
	#include <linux/ftrace.h>
	#include <linux/errno.h>
	#include <linux/slab.h>
	#include <linux/init.h>
	#include <linux/cpu.h>
	#include <linux/irq.h>
	#include <asm/irq_regs.h>
	#include <asm/cputime.h>
	#include <asm/lowcore.h>
	#include <asm/irq.h>
	#include <asm/hw_irq.h>
	#include <asm/stacktrace.h>
	#include "entry.h"

	DEFINE_PER_CPU_SHARED_ALIGNED(struct irq_stat, irq_stat);
	EXPORT_PER_CPU_SYMBOL_GPL(irq_stat);

	struct irq_class {
	int irq;
	char *name;
	char *desc;
	};

	/*
	* The list of "main" irq classes on s390. This is the list of interrupts
	* that appear both in /proc/stat ("intr" line) and /proc/interrupts.
	* Historically only external and I/O interrupts have been part of /proc/stat.
	* We can't add the split external and I/O sub classes since the first field
	* in the "intr" line in /proc/stat is supposed to be the sum of all other
	* fields.
	* Since the external and I/O interrupt fields are already sums we would end
	* up with having a sum which accounts each interrupt twice.
	*/
	static const struct irq_class irqclass_main_desc[NR_IRQS_BASE] = {
	{.irq = EXT_INTERRUPT, .name = "EXT"},
	{.irq = IO_INTERRUPT, .name = "I/O"},
	{.irq = THIN_INTERRUPT, .name = "AIO"},
	};

	/*
	* The list of split external and I/O interrupts that appear only in
	* /proc/interrupts.
	* In addition this list contains non external / I/O events like NMIs.
	*/
	static const struct irq_class irqclass_sub_desc[] = {
	{.irq = IRQEXT_CLK, .name = "CLK", .desc = "[EXT] Clock Comparator"},
	{.irq = IRQEXT_EXC, .name = "EXC", .desc = "[EXT] External Call"},
	{.irq = IRQEXT_EMS, .name = "EMS", .desc = "[EXT] Emergency Signal"},
	{.irq = IRQEXT_TMR, .name = "TMR", .desc = "[EXT] CPU Timer"},
	{.irq = IRQEXT_TLA, .name = "TAL", .desc = "[EXT] Timing Alert"},
	{.irq = IRQEXT_PFL, .name = "PFL", .desc = "[EXT] Pseudo Page Fault"},
	{.irq = IRQEXT_DSD, .name = "DSD", .desc = "[EXT] DASD Diag"},
	{.irq = IRQEXT_VRT, .name = "VRT", .desc = "[EXT] Virtio"},
	{.irq = IRQEXT_SCP, .name = "SCP", .desc = "[EXT] Service Call"},
	{.irq = IRQEXT_IUC, .name = "IUC", .desc = "[EXT] IUCV"},
	{.irq = IRQEXT_CMS, .name = "CMS", .desc = "[EXT] CPU-Measurement: Sampling"},
	{.irq = IRQEXT_CMC, .name = "CMC", .desc = "[EXT] CPU-Measurement: Counter"},
	{.irq = IRQEXT_FTP, .name = "FTP", .desc = "[EXT] HMC FTP Service"},
	{.irq = IRQIO_CIO, .name = "CIO", .desc = "[I/O] Common I/O Layer Interrupt"},
	{.irq = IRQIO_DAS, .name = "DAS", .desc = "[I/O] DASD"},
	{.irq = IRQIO_C15, .name = "C15", .desc = "[I/O] 3215"},
	{.irq = IRQIO_C70, .name = "C70", .desc = "[I/O] 3270"},
	{.irq = IRQIO_TAP, .name = "TAP", .desc = "[I/O] Tape"},
	{.irq = IRQIO_VMR, .name = "VMR", .desc = "[I/O] Unit Record Devices"},
	{.irq = IRQIO_LCS, .name = "LCS", .desc = "[I/O] LCS"},
	{.irq = IRQIO_CTC, .name = "CTC", .desc = "[I/O] CTC"},
	{.irq = IRQIO_ADM, .name = "ADM", .desc = "[I/O] EADM Subchannel"},
	{.irq = IRQIO_CSC, .name = "CSC", .desc = "[I/O] CHSC Subchannel"},
	{.irq = IRQIO_VIR, .name = "VIR", .desc = "[I/O] Virtual I/O Devices"},
	{.irq = IRQIO_QAI, .name = "QAI", .desc = "[AIO] QDIO Adapter Interrupt"},
	{.irq = IRQIO_APB, .name = "APB", .desc = "[AIO] AP Bus"},
	{.irq = IRQIO_PCF, .name = "PCF", .desc = "[AIO] PCI Floating Interrupt"},
	{.irq = IRQIO_PCD, .name = "PCD", .desc = "[AIO] PCI Directed Interrupt"},
	{.irq = IRQIO_MSI, .name = "MSI", .desc = "[AIO] MSI Interrupt"},
	{.irq = IRQIO_VAI, .name = "VAI", .desc = "[AIO] Virtual I/O Devices AI"},
	{.irq = IRQIO_GAL, .name = "GAL", .desc = "[AIO] GIB Alert"},
	{.irq = NMI_NMI, .name = "NMI", .desc = "[NMI] Machine Check"},
	{.irq = CPU_RST, .name = "RST", .desc = "[CPU] CPU Restart"},
	};

	void __init init_IRQ(void)
	{
	BUILD_BUG_ON(ARRAY_SIZE(irqclass_sub_desc) != NR_ARCH_IRQS);
	init_cio_interrupts();
	init_airq_interrupts();
	init_ext_interrupts();
	}

	void do_IRQ(struct pt_regs *regs, int irq)
	{
	struct pt_regs *old_regs;

	old_regs = set_irq_regs(regs);
	irq_enter();
	if (tod_after_eq(S390_lowcore.int_clock,
	S390_lowcore.clock_comparator))
	/* Serve timer interrupts first. */
	clock_comparator_work();
	generic_handle_irq(irq);
	irq_exit();
	set_irq_regs(old_regs);
	}

	static void show_msi_interrupt(struct seq_file *p, int irq)
	{
	struct irq_desc *desc;
	unsigned long flags;
	int cpu;

	irq_lock_sparse();
	desc = irq_to_desc(irq);
	if (!desc)
	goto out;

	raw_spin_lock_irqsave(&desc->lock, flags);
	seq_printf(p, "%3d: ", irq);
	for_each_online_cpu(cpu)
	seq_printf(p, "%10u ", kstat_irqs_cpu(irq, cpu));

	if (desc->irq_data.chip)
	seq_printf(p, " %8s", desc->irq_data.chip->name);

	if (desc->action)
	seq_printf(p, " %s", desc->action->name);

	seq_putc(p, '\n');
	raw_spin_unlock_irqrestore(&desc->lock, flags);
	out:
	irq_unlock_sparse();
	}

	/*
	* show_interrupts is needed by /proc/interrupts.
	*/
	int show_interrupts(struct seq_file p, void v)
	{
	int index = (loff_t ) v;
	int cpu, irq;

	get_online_cpus();
	if (index == 0) {
	seq_puts(p, " ");
	for_each_online_cpu(cpu)
	seq_printf(p, "CPU%-8d", cpu);
	seq_putc(p, '\n');
	}
	if (index < NR_IRQS_BASE) {
	seq_printf(p, "%s: ", irqclass_main_desc[index].name);
	irq = irqclass_main_desc[index].irq;
	for_each_online_cpu(cpu)
	seq_printf(p, "%10u ", kstat_irqs_cpu(irq, cpu));
	seq_putc(p, '\n');
	goto out;
	}
	if (index < nr_irqs) {
	show_msi_interrupt(p, index);
	goto out;
	}
	for (index = 0; index < NR_ARCH_IRQS; index++) {
	seq_printf(p, "%s: ", irqclass_sub_desc[index].name);
	irq = irqclass_sub_desc[index].irq;
	for_each_online_cpu(cpu)
	seq_printf(p, "%10u ",
	per_cpu(irq_stat, cpu).irqs[irq]);
	if (irqclass_sub_desc[index].desc)
	seq_printf(p, " %s", irqclass_sub_desc[index].desc);
	seq_putc(p, '\n');
	}
	out:
	put_online_cpus();
	return 0;
	}

	unsigned int arch_dynirq_lower_bound(unsigned int from)
	{
	return from < NR_IRQS_BASE ? NR_IRQS_BASE : from;
	}

	/*
	* Switch to the asynchronous interrupt stack for softirq execution.
	*/
	void do_softirq_own_stack(void)
	{
	unsigned long old, new;

	old = current_stack_pointer();
	/* Check against async. stack address range. */
	new = S390_lowcore.async_stack;
	if (((new - old) >> (PAGE_SHIFT + THREAD_SIZE_ORDER)) != 0) {
	CALL_ON_STACK(__do_softirq, new, 0);
	} else {
	/* We are already on the async stack. */
	__do_softirq();
	}
	}

	/*
	* ext_int_hash[index] is the list head for all external interrupts that hash
	* to this index.
	*/
	static struct hlist_head ext_int_hash[32] ____cacheline_aligned;

	struct ext_int_info {
	ext_int_handler_t handler;
	struct hlist_node entry;
	struct rcu_head rcu;
	u16 code;
	};

	/* ext_int_hash_lock protects the handler lists for external interrupts */
	static DEFINE_SPINLOCK(ext_int_hash_lock);

	static inline int ext_hash(u16 code)
	{
	BUILD_BUG_ON(!is_power_of_2(ARRAY_SIZE(ext_int_hash)));

	return (code + (code >> 9)) & (ARRAY_SIZE(ext_int_hash) - 1);
	}

	int register_external_irq(u16 code, ext_int_handler_t handler)
	{
	struct ext_int_info *p;
	unsigned long flags;
	int index;

	p = kmalloc(sizeof(*p), GFP_ATOMIC);
	if (!p)
	return -ENOMEM;
	p->code = code;
	p->handler = handler;
	index = ext_hash(code);

	spin_lock_irqsave(&ext_int_hash_lock, flags);
	hlist_add_head_rcu(&p->entry, &ext_int_hash[index]);
	spin_unlock_irqrestore(&ext_int_hash_lock, flags);
	return 0;
	}
	EXPORT_SYMBOL(register_external_irq);

	int unregister_external_irq(u16 code, ext_int_handler_t handler)
	{
	struct ext_int_info *p;
	unsigned long flags;
	int index = ext_hash(code);

	spin_lock_irqsave(&ext_int_hash_lock, flags);
	hlist_for_each_entry_rcu(p, &ext_int_hash[index], entry) {
	if (p->code == code && p->handler == handler) {
	hlist_del_rcu(&p->entry);
	kfree_rcu(p, rcu);
	}
	}
	spin_unlock_irqrestore(&ext_int_hash_lock, flags);
	return 0;
	}
	EXPORT_SYMBOL(unregister_external_irq);

	static irqreturn_t do_ext_interrupt(int irq, void *dummy)
	{
	struct pt_regs *regs = get_irq_regs();
	struct ext_code ext_code;
	struct ext_int_info *p;
	int index;

	ext_code = (struct ext_code ) &regs->int_code;
	if (ext_code.code != EXT_IRQ_CLK_COMP)
	set_cpu_flag(CIF_NOHZ_DELAY);

	index = ext_hash(ext_code.code);
	rcu_read_lock();
	hlist_for_each_entry_rcu(p, &ext_int_hash[index], entry) {
	if (unlikely(p->code != ext_code.code))
	continue;
	p->handler(ext_code, regs->int_parm, regs->int_parm_long);
	}
	rcu_read_unlock();
	return IRQ_HANDLED;
	}

	static struct irqaction external_interrupt = {
	.name = "EXT",
	.handler = do_ext_interrupt,
	};

	void __init init_ext_interrupts(void)
	{
	int idx;

	for (idx = 0; idx < ARRAY_SIZE(ext_int_hash); idx++)
	INIT_HLIST_HEAD(&ext_int_hash[idx]);

	irq_set_chip_and_handler(EXT_INTERRUPT,
	&dummy_irq_chip, handle_percpu_irq);
	setup_irq(EXT_INTERRUPT, &external_interrupt);
	}

	static DEFINE_SPINLOCK(irq_subclass_lock);
	static unsigned char irq_subclass_refcount[64];

	void irq_subclass_register(enum irq_subclass subclass)
	{
	spin_lock(&irq_subclass_lock);
	if (!irq_subclass_refcount[subclass])
	ctl_set_bit(0, subclass);
	irq_subclass_refcount[subclass]++;
	spin_unlock(&irq_subclass_lock);
	}
	EXPORT_SYMBOL(irq_subclass_register);

	void irq_subclass_unregister(enum irq_subclass subclass)
	{
	spin_lock(&irq_subclass_lock);
	irq_subclass_refcount[subclass]--;
	if (!irq_subclass_refcount[subclass])
	ctl_clear_bit(0, subclass);
	spin_unlock(&irq_subclass_lock);
	}
	EXPORT_SYMBOL(irq_subclass_unregister);