/*
 *  arch/s390/kernel/irq.c
 *
 *  S390 version
 *    Copyright (C) 1999,2000 IBM Deutschland Entwicklung GmbH, IBM Corporation
 *    Author(s): Ingo Adlung (adlung@de.ibm.com)
 *
 *  Derived from "arch/i386/kernel/irq.c"
 *    Copyright (C) 1992, 1999 Linus Torvalds, Ingo Molnar
 *
 *  S/390 I/O interrupt processing and I/O request processing is
 *   implemented in arch/s390/kernel/s390io.c
 */
#include <linux/ptrace.h>
#include <linux/errno.h>
#include <linux/kernel_stat.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/timex.h>
#include <linux/malloc.h>
#include <linux/string.h>
#include <linux/random.h>
#include <linux/smp.h>
#include <linux/tasks.h>
#include <linux/smp_lock.h>
#include <linux/init.h>

#include <asm/system.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/bitops.h>
#include <asm/smp.h>
#include <asm/pgtable.h>
#include <asm/delay.h>
#include <asm/lowcore.h>

unsigned long s390_init_IRQ(unsigned long);
void s390_free_irq(unsigned int irq, void *dev_id);
int  s390_request_irq( unsigned int   irq,
                       void           (*handler)(int, void *, struct pt_regs *),
                       unsigned long  irqflags,
                       const char    *devname,
                       void          *dev_id);

atomic_t nmi_counter;

spinlock_t s390_bh_lock = SPIN_LOCK_UNLOCKED;

#if 0
/*
 * The following vectors are part of the Linux architecture, there
 * is no hardware IRQ pin equivalent for them, they are triggered
 * through the ICC by us (IPIs), via smp_message_pass():
 */
BUILD_SMP_INTERRUPT(reschedule_interrupt)
BUILD_SMP_INTERRUPT(invalidate_interrupt)
BUILD_SMP_INTERRUPT(stop_cpu_interrupt)
BUILD_SMP_INTERRUPT(mtrr_interrupt)
BUILD_SMP_INTERRUPT(spurious_interrupt)
#endif

#if 0
int get_irq_list(char *buf)
{
	int i, j;
	struct irqaction * action;
	char *p = buf;

	p += sprintf(p, "           ");

	for (j=0; j<smp_num_cpus; j++)
		p += sprintf(p, "CPU%d       ",j);

	*p++ = '\n';

	for (i = 0 ; i < NR_IRQS ; i++)
	{
		if (ioinfo[i] == INVALID_STORAGE_AREA)
			continue;

		action = ioinfo[i]->irq_desc.action;
		
		if (!action)
			continue;

		p += sprintf(p, "%3d: ",i);
#ifndef __SMP__
		p += sprintf(p, "%10u ", kstat_irqs(i));
#else
		for (j=0; j<smp_num_cpus; j++)
			p += sprintf(p, "%10u ",
				     kstat.irqs[cpu_logical_map(j)][i]);
#endif
		p += sprintf(p, " %14s", ioinfo[i]->irq_desc.handler->typename);
		p += sprintf(p, "  %s", action->name);

		for (action=action->next; action; action = action->next)
		{
			p += sprintf(p, ", %s", action->name);

		} /* endfor */

		*p++ = '\n';
	
	} /* endfor */

	p += sprintf(p, "NMI: %10u\n", atomic_read(&nmi_counter));
#ifdef __SMP__
	p += sprintf(p, "IPI: %10u\n", atomic_read(&ipi_count));
#endif

	return p - buf;
}
#endif

/*
 * Global interrupt locks for SMP. Allow interrupts to come in on any
 * CPU, yet make cli/sti act globally to protect critical regions..
 */
#ifdef __SMP__
atomic_t global_irq_holder = ATOMIC_INIT(NO_PROC_ID);
atomic_t global_irq_lock;
atomic_t global_irq_count = ATOMIC_INIT(0);

atomic_t global_bh_count;
atomic_t global_bh_lock;

/*
 * "global_cli()" is a special case, in that it can hold the
 * interrupts disabled for a longish time, and also because
 * we may be doing TLB invalidates when holding the global
 * IRQ lock for historical reasons. Thus we may need to check
 * SMP invalidate events specially by hand here (but not in
 * any normal spinlocks)
 *
 * Thankfully we don't need this as we can deliver flush tlbs with
 * interrupts disabled DJB :-)
 */
#define check_smp_invalidate(cpu)

static void show(char * str)
{
	int i;
	unsigned long *stack;
	int cpu = smp_processor_id();

	printk("\n%s, CPU %d:\n", str, cpu);
	printk("irq:  %d [%d]\n",
	       atomic_read(&global_irq_count),atomic_read(&S390_lowcore.local_irq_count));
	printk("bh:   %d [%d]\n",
	       atomic_read(&global_bh_count),atomic_read(&S390_lowcore.local_bh_count));
	stack = (unsigned long *) &str;
	for (i = 40; i ; i--) {
		unsigned long x = *++stack;
		if (x > (unsigned long) &init_task_union && x < (unsigned long) &vsprintf) {
			printk("<[%08lx]> ", x);
		}
	}
}

#define MAXCOUNT 100000000

static inline void wait_on_bh(void)
{
	int count = MAXCOUNT;
	do {
		if (!--count) {
			show("wait_on_bh");
			count = ~0;
		}
		/* nothing .. wait for the other bh's to go away */
	} while (atomic_read(&global_bh_count) != 0);
}

static inline void wait_on_irq(int cpu)
{
	int count = MAXCOUNT;

	for (;;) {

		/*
		 * Wait until all interrupts are gone. Wait
		 * for bottom half handlers unless we're
		 * already executing in one..
		 */
		if (!atomic_read(&global_irq_count)) {
			if (atomic_read(&safe_get_cpu_lowcore(cpu).local_bh_count)||
			    !atomic_read(&global_bh_count))
				break;
		}

		/* Duh, we have to loop. Release the lock to avoid deadlocks */
		clear_bit(0,&global_irq_lock);

		for (;;) {
			if (!--count) {
				show("wait_on_irq");
				count = ~0;
			}
			__sti();
			SYNC_OTHER_CORES(cpu);
			__cli();
			check_smp_invalidate(cpu);
			if (atomic_read(&global_irq_count))
				continue;
			if (atomic_read(&global_irq_lock))
				continue;
			if (!(atomic_read(&safe_get_cpu_lowcore(cpu).local_bh_count))
			    && atomic_read(&global_bh_count))
				continue;
			if (!test_and_set_bit(0,&global_irq_lock))
				break;
		}
	}
}

/*
 * This is called when we want to synchronize with
 * bottom half handlers. We need to wait until
 * no other CPU is executing any bottom half handler.
 *
 * Don't wait if we're already running in an interrupt
 * context or are inside a bh handler.
 */
void synchronize_bh(void)
{
	if (atomic_read(&global_bh_count) && !in_interrupt())
		wait_on_bh();
}

/*
 * This is called when we want to synchronize with
 * interrupts. We may for example tell a device to
 * stop sending interrupts: but to make sure there
 * are no interrupts that are executing on another
 * CPU we need to call this function.
 */
void synchronize_irq(void)
{
	if (atomic_read(&global_irq_count)) {
		/* Stupid approach */
		cli();
		sti();
	}
}

static inline void get_irqlock(int cpu)
{
	if (test_and_set_bit(0,&global_irq_lock)) {
		/* do we already hold the lock? */
		if ( cpu == atomic_read(&global_irq_holder))
			return;
		/* Uhhuh.. Somebody else got it. Wait.. */
		do {
			do {
				check_smp_invalidate(cpu);
			} while (test_bit(0,&global_irq_lock));
		} while (test_and_set_bit(0,&global_irq_lock));
	}
	/*
	 * We also to make sure that nobody else is running
	 * in an interrupt context.
	 */
	wait_on_irq(cpu);

	/*
	 * Ok, finally..
	 */
	atomic_set(&global_irq_holder,cpu);
}

#define EFLAGS_I_SHIFT 25

/*
 * A global "cli()" while in an interrupt context
 * turns into just a local cli(). Interrupts
 * should use spinlocks for the (very unlikely)
 * case that they ever want to protect against
 * each other.
 *
 * If we already have local interrupts disabled,
 * this will not turn a local disable into a
 * global one (problems with spinlocks: this makes
 * save_flags+cli+sti usable inside a spinlock).
 */
void __global_cli(void)
{
	unsigned int flags;

	__save_flags(flags);
	if (flags & (1 << EFLAGS_I_SHIFT)) {
		int cpu = smp_processor_id();
		__cli();
		if (!atomic_read(&S390_lowcore.local_irq_count))
			get_irqlock(cpu);
	}
}

void __global_sti(void)
{

	if (!atomic_read(&S390_lowcore.local_irq_count))
		release_irqlock(smp_processor_id());
	__sti();
}

/*
 * SMP flags value to restore to:
 * 0 - global cli
 * 1 - global sti
 * 2 - local cli
 * 3 - local sti
 */
unsigned long __global_save_flags(void)
{
	int retval;
	int local_enabled;
	unsigned long flags;

	__save_flags(flags);
	local_enabled = (flags >> EFLAGS_I_SHIFT) & 1;
	/* default to local */
	retval = 2 + local_enabled;

	/* check for global flags if we're not in an interrupt */
	if (!atomic_read(&S390_lowcore.local_irq_count))
	{
		if (local_enabled)
			retval = 1;
		if (atomic_read(&global_irq_holder)== smp_processor_id())
			retval = 0;
	}
	return retval;
}

void __global_restore_flags(unsigned long flags)
{
	switch (flags) {
	case 0:
		__global_cli();
		break;
	case 1:
		__global_sti();
		break;
	case 2:
		__cli();
		break;
	case 3:
		__sti();
		break;
	default:
		printk("global_restore_flags: %08lx (%08lx)\n",
		       flags, (&flags)[-1]);
	}
}

#endif

/*
 * Note : This fuction should be eliminated as it doesn't comply with the
 *         S/390 irq scheme we have implemented ...
 */
int handle_IRQ_event(unsigned int irq, int cpu, struct pt_regs * regs)
{
	struct irqaction * action;
	int                status;

	status = 0;

	if ( ioinfo[irq] == INVALID_STORAGE_AREA )
		return( -ENODEV);

	action = ioinfo[irq]->irq_desc.action;

	if (action)
	{
		status |= 1;

		if (!(action->flags & SA_INTERRUPT))
			__sti();

		do
		{
			status |= action->flags;
			action->handler(irq, action->dev_id, regs);
			action = action->next;
		} while (action);

		if (status & SA_SAMPLE_RANDOM)
			add_interrupt_randomness(irq);
		__cli();

	} /* endif */

	return status;
}

void enable_nop(int irq)
{
}

unsigned long __init init_IRQ(unsigned long memory)
{
	return s390_init_IRQ( memory);
}


void free_irq(unsigned int irq, void *dev_id)
{
	s390_free_irq( irq, dev_id);
}


int request_irq( unsigned int   irq,
                 void           (*handler)(int, void *, struct pt_regs *),
                 unsigned long  irqflags,
                 const char    *devname,
                 void          *dev_id)
{
	return( s390_request_irq( irq, handler, irqflags, devname, dev_id ) );
}