Import 2.3.16pre1

[davej-history.git] / arch / i386 / kernel / irq.c

/* mostly architecture independent
   some moved to i8259.c
   the beautiful visws architecture code needs to be updated too.
   and, finally, the BUILD_IRQ and SMP_BUILD macros in irq.h need fixed.
   */
/*
 *      linux/arch/i386/kernel/irq.c
 *
 *      Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
 *
 * 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.
 */

/*
 * IRQs are in fact implemented a bit like signal handlers for the kernel.
 * Naturally it's not a 1:1 relation, but there are similarities.
 */

#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/random.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/init.h>

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


unsigned int local_bh_count[NR_CPUS];
unsigned int local_irq_count[NR_CPUS];

atomic_t nmi_counter;

/*
 * Linux has a controller-independent x86 interrupt architecture.
 * every controller has a 'controller-template', that is used
 * by the main code to do the right thing. Each driver-visible
 * interrupt source is transparently wired to the apropriate
 * controller. Thus drivers need not be aware of the
 * interrupt-controller.
 *
 * Various interrupt controllers we handle: 8259 PIC, SMP IO-APIC,
 * PIIX4's internal 8259 PIC and SGI's Visual Workstation Cobalt (IO-)APIC.
 * (IO-APICs assumed to be messaging to Pentium local-APICs)
 *
 * the code is designed to be easily extended with new/different
 * interrupt controllers, without having to do assembly magic.
 */

/*
 * Micro-access to controllers is serialized over the whole
 * system. We never hold this lock when we call the actual
 * IRQ handler.
 */
spinlock_t irq_controller_lock = SPIN_LOCK_UNLOCKED;
/*
 * Controller mappings for all interrupt sources:
 */
irq_desc_t irq_desc[NR_IRQS] __cacheline_aligned = { [0 ... NR_IRQS-1] = { 0, &no_irq_type, }};

/*
 * Special irq handlers.
 */

void no_action(int cpl, void *dev_id, struct pt_regs *regs) { }

/*
 * Generic, controller-independent functions:
 */

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++) {
                action = irq_desc[i].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", irq_desc[i].handler->typename);
                p += sprintf(p, "  %s", action->name);

                for (action=action->next; action; action = action->next) {
                        p += sprintf(p, ", %s", action->name);
                }
                *p++ = '\n';
        }
        p += sprintf(p, "NMI: %10u\n", atomic_read(&nmi_counter));
#ifdef __SMP__
        p += sprintf(p, "ERR: %10lu\n", ipi_count);
#endif          
        return p - buf;
}

/*
 * 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__
unsigned char global_irq_holder = NO_PROC_ID;
unsigned volatile int global_irq_lock;
atomic_t global_irq_count;

atomic_t global_bh_count;
atomic_t global_bh_lock;
spinlock_t i386_bh_lock = SPIN_LOCK_UNLOCKED;

/*
 * "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)
 */
static inline void check_smp_invalidate(int cpu)
{
        if (test_bit(cpu, &smp_invalidate_needed)) {
                struct mm_struct *mm = current->mm;
                clear_bit(cpu, &smp_invalidate_needed);
                if (mm)
                        atomic_set_mask(1 << cpu, &mm->cpu_vm_mask);
                local_flush_tlb();
        }
}

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 %d]\n",
                atomic_read(&global_irq_count), local_irq_count[0], local_irq_count[1]);
        printk("bh:   %d [%d %d]\n",
                atomic_read(&global_bh_count), local_bh_count[0], local_bh_count[1]);
        stack = (unsigned long *) &stack;
        for (i = 40; i ; i--) {
                unsigned long x = *++stack;
                if (x > (unsigned long) &get_option && 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);
}

/*
 * I had a lockup scenario where a tight loop doing
 * spin_unlock()/spin_lock() on CPU#1 was racing with
 * spin_lock() on CPU#0. CPU#0 should have noticed spin_unlock(), but
 * apparently the spin_unlock() information did not make it
 * through to CPU#0 ... nasty, is this by design, do we have to limit
 * 'memory update oscillation frequency' artificially like here?
 *
 * Such 'high frequency update' races can be avoided by careful design, but
 * some of our major constructs like spinlocks use similar techniques,
 * it would be nice to clarify this issue. Set this define to 0 if you
 * want to check whether your system freezes.  I suspect the delay done
 * by SYNC_OTHER_CORES() is in correlation with 'snooping latency', but
 * i thought that such things are guaranteed by design, since we use
 * the 'LOCK' prefix.
 */
#define SUSPECTED_CPU_OR_CHIPSET_BUG_WORKAROUND 1

#if SUSPECTED_CPU_OR_CHIPSET_BUG_WORKAROUND
# define SYNC_OTHER_CORES(x) udelay(x+1)
#else
/*
 * We have to allow irqs to arrive between __sti and __cli
 */
# define SYNC_OTHER_CORES(x) __asm__ __volatile__ ("nop")
#endif

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 (local_bh_count[cpu] || !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 (global_irq_lock)
                                continue;
                        if (!local_bh_count[cpu] && 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 ((unsigned char) cpu == 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..
         */
        global_irq_holder = cpu;
}

#define EFLAGS_IF_SHIFT 9

/*
 * 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_IF_SHIFT)) {
                int cpu = smp_processor_id();
                __cli();
                if (!local_irq_count[cpu])
                        get_irqlock(cpu);
        }
}

void __global_sti(void)
{
        int cpu = smp_processor_id();

        if (!local_irq_count[cpu])
                release_irqlock(cpu);
        __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_IF_SHIFT) & 1;
        /* default to local */
        retval = 2 + local_enabled;

        /* check for global flags if we're not in an interrupt */
        if (!local_irq_count[smp_processor_id()]) {
                if (local_enabled)
                        retval = 1;
                if (global_irq_holder == (unsigned char) 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

/*
 * This should really return information about whether
 * we should do bottom half handling etc. Right now we
 * end up _always_ checking the bottom half, which is a
 * waste of time and is not what some drivers would
 * prefer.
 */
int handle_IRQ_event(unsigned int irq, struct pt_regs * regs, struct irqaction * action)
{
        int status;
        int cpu = smp_processor_id();

        irq_enter(cpu, irq);

        status = 1;     /* Force the "do bottom halves" bit */

        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();

        irq_exit(cpu, irq);

        return status;
}

/*
 * Generic enable/disable code: this just calls
 * down into the PIC-specific version for the actual
 * hardware disable after having gotten the irq
 * controller lock. 
 */
void disable_irq_nosync(unsigned int irq)
{
        unsigned long flags;

        spin_lock_irqsave(&irq_controller_lock, flags);
        if (!irq_desc[irq].depth++) {
                irq_desc[irq].status |= IRQ_DISABLED;
                irq_desc[irq].handler->disable(irq);
        }
        spin_unlock_irqrestore(&irq_controller_lock, flags);
}

/*
 * Synchronous version of the above, making sure the IRQ is
 * no longer running on any other IRQ..
 */
void disable_irq(unsigned int irq)
{
        disable_irq_nosync(irq);

        if (!local_irq_count[smp_processor_id()]) {
                do {
                        barrier();
                } while (irq_desc[irq].status & IRQ_INPROGRESS);
        }
}

void enable_irq(unsigned int irq)
{
        unsigned long flags;

        spin_lock_irqsave(&irq_controller_lock, flags);
        switch (irq_desc[irq].depth) {
        case 1: {
                unsigned int status = irq_desc[irq].status & ~IRQ_DISABLED;
                irq_desc[irq].status = status;
                if ((status & (IRQ_PENDING | IRQ_REPLAY)) == IRQ_PENDING) {
                        irq_desc[irq].status = status | IRQ_REPLAY;
                        hw_resend_irq(irq_desc[irq].handler,irq);
                }
                irq_desc[irq].handler->enable(irq);
                /* fall-through */
        }
        default:
                irq_desc[irq].depth--;
                break;
        case 0:
                printk("enable_irq() unbalanced from %p\n",
                       __builtin_return_address(0));
        }
        spin_unlock_irqrestore(&irq_controller_lock, flags);
}

/*
 * do_IRQ handles all normal device IRQ's (the special
 * SMP cross-CPU interrupts have their own specific
 * handlers).
 */
asmlinkage unsigned int do_IRQ(struct pt_regs regs)
{       
        /* 
         * We ack quickly, we don't want the irq controller
         * thinking we're snobs just because some other CPU has
         * disabled global interrupts (we have already done the
         * INT_ACK cycles, it's too late to try to pretend to the
         * controller that we aren't taking the interrupt).
         *
         * 0 return value means that this irq is already being
         * handled by some other CPU. (or is disabled)
         */
        int irq = regs.orig_eax & 0xff; /* high bits used in ret_from_ code  */
        int cpu = smp_processor_id();
        irq_desc_t *desc;
        struct irqaction * action;
        unsigned int status;

        kstat.irqs[cpu][irq]++;
        desc = irq_desc + irq;
        spin_lock(&irq_controller_lock);
        irq_desc[irq].handler->ack(irq);
        /*
           REPLAY is when Linux resends an IRQ that was dropped earlier
           WAITING is used by probe to mark irqs that are being tested
           */
        status = desc->status & ~(IRQ_REPLAY | IRQ_WAITING);
        status |= IRQ_PENDING; /* we _want_ to handle it */

        /*
         * If the IRQ is disabled for whatever reason, we cannot
         * use the action we have.
         */
        action = NULL;
        if (!(status & (IRQ_DISABLED | IRQ_INPROGRESS))) {
                action = desc->action;
                status &= ~IRQ_PENDING; /* we commit to handling */
                status |= IRQ_INPROGRESS; /* we are handling it */
        }
        desc->status = status;
        spin_unlock(&irq_controller_lock);

        /*
         * If there is no IRQ handler or it was disabled, exit early.
           Since we set PENDING, if another processor is handling
           a different instance of this same irq, the other processor
           will take care of it.
         */
        if (!action)
                return 1;

        /*
         * Edge triggered interrupts need to remember
         * pending events.
         * This applies to any hw interrupts that allow a second
         * instance of the same irq to arrive while we are in do_IRQ
         * or in the handler. But the code here only handles the _second_
         * instance of the irq, not the third or fourth. So it is mostly
         * useful for irq hardware that does not mask cleanly in an
         * SMP environment.
         */
        for (;;) {
                handle_IRQ_event(irq, &regs, action);
                spin_lock(&irq_controller_lock);
                
                if (!(desc->status & IRQ_PENDING))
                        break;
                desc->status &= ~IRQ_PENDING;
                spin_unlock(&irq_controller_lock);
        }
        desc->status &= ~IRQ_INPROGRESS;
        if (!(desc->status & IRQ_DISABLED)){
                        irq_desc[irq].handler->end(irq);
        }
        spin_unlock(&irq_controller_lock);

        /*
         * This should be conditional: we should really get
         * a return code from the irq handler to tell us
         * whether the handler wants us to do software bottom
         * half handling or not..
         */
        if (1) {
                if (bh_active & bh_mask)
                        do_bottom_half();
        }
        return 1;
}

int request_irq(unsigned int irq, 
                void (*handler)(int, void *, struct pt_regs *),
                unsigned long irqflags, 
                const char * devname,
                void *dev_id)
{
        int retval;
        struct irqaction * action;

        if (irq >= NR_IRQS)
                return -EINVAL;
        if (!handler)
                return -EINVAL;

        action = (struct irqaction *)
                        kmalloc(sizeof(struct irqaction), GFP_KERNEL);
        if (!action)
                return -ENOMEM;

        action->handler = handler;
        action->flags = irqflags;
        action->mask = 0;
        action->name = devname;
        action->next = NULL;
        action->dev_id = dev_id;

        retval = setup_irq(irq, action);
        if (retval)
                kfree(action);
        return retval;
}
                
void free_irq(unsigned int irq, void *dev_id)
{
        struct irqaction **p;
        unsigned long flags;

        if (irq >= NR_IRQS)
                return;

        spin_lock_irqsave(&irq_controller_lock,flags);
        p = &irq_desc[irq].action;
        for (;;) {
                struct irqaction * action = *p;
                if (action) {
                        struct irqaction **pp = p;
                        p = &action->next;
                        if (action->dev_id != dev_id)
                                continue;

                        /* Found it - now remove it from the list of entries */
                        *pp = action->next;
                        if (!irq_desc[irq].action) {
                                irq_desc[irq].status |= IRQ_DISABLED;
                                irq_desc[irq].handler->shutdown(irq);
                        }
                        spin_unlock_irqrestore(&irq_controller_lock,flags);

                        /* Wait to make sure it's not being used on another CPU */
                        while (irq_desc[irq].status & IRQ_INPROGRESS)
                                barrier();
                        kfree(action);
                        return;
                }
                printk("Trying to free free IRQ%d\n",irq);
                spin_unlock_irqrestore(&irq_controller_lock,flags);
                return;
        }
}

/*
 * IRQ autodetection code..
 *
 * This depends on the fact that any interrupt that
 * comes in on to an unassigned handler will get stuck
 * with "IRQ_WAITING" cleared and the interrupt
 * disabled.
 */
unsigned long probe_irq_on(void)
{
        unsigned int i;
        unsigned long delay;

        /*
         * first, enable any unassigned irqs
         */
        spin_lock_irq(&irq_controller_lock);
        for (i = NR_IRQS-1; i > 0; i--) {
                if (!irq_desc[i].action) {
                        irq_desc[i].status |= IRQ_AUTODETECT | IRQ_WAITING;
                        if(irq_desc[i].handler->startup(i))
                                irq_desc[i].status |= IRQ_PENDING;
                }
        }
        spin_unlock_irq(&irq_controller_lock);

        /*
         * Wait for spurious interrupts to trigger
         */
        for (delay = jiffies + HZ/10; time_after(delay, jiffies); )
                /* about 100ms delay */ synchronize_irq();

        /*
         * Now filter out any obviously spurious interrupts
         */
        spin_lock_irq(&irq_controller_lock);
        for (i=0; i<NR_IRQS; i++) {
                unsigned int status = irq_desc[i].status;

                if (!(status & IRQ_AUTODETECT))
                        continue;
                
                /* It triggered already - consider it spurious. */
                if (!(status & IRQ_WAITING)) {
                        irq_desc[i].status = status & ~IRQ_AUTODETECT;
                        irq_desc[i].handler->shutdown(i);
                }
        }
        spin_unlock_irq(&irq_controller_lock);

        return 0x12345678;
}

int probe_irq_off(unsigned long unused)
{
        int i, irq_found, nr_irqs;

        if (unused != 0x12345678)
                printk("Bad IRQ probe from %lx\n", (&unused)[-1]);

        nr_irqs = 0;
        irq_found = 0;
        spin_lock_irq(&irq_controller_lock);
        for (i=0; i<NR_IRQS; i++) {
                unsigned int status = irq_desc[i].status;

                if (!(status & IRQ_AUTODETECT))
                        continue;

                if (!(status & IRQ_WAITING)) {
                        if (!nr_irqs)
                                irq_found = i;
                        nr_irqs++;
                }
                irq_desc[i].status = status & ~IRQ_AUTODETECT;
                irq_desc[i].handler->shutdown(i);
        }
        spin_unlock_irq(&irq_controller_lock);

        if (nr_irqs > 1)
                irq_found = -irq_found;
        return irq_found;
}

/* this was setup_x86_irq but it seems pretty generic */
int setup_irq(unsigned int irq, struct irqaction * new)
{
        int shared = 0;
        struct irqaction *old, **p;
        unsigned long flags;

        /*
         * Some drivers like serial.c use request_irq() heavily,
         * so we have to be careful not to interfere with a
         * running system.
         */
        if (new->flags & SA_SAMPLE_RANDOM) {
                /*
                 * This function might sleep, we want to call it first,
                 * outside of the atomic block.
                 * Yes, this might clear the entropy pool if the wrong
                 * driver is attempted to be loaded, without actually
                 * installing a new handler, but is this really a problem,
                 * only the sysadmin is able to do this.
                 */
                rand_initialize_irq(irq);
        }

        /*
         * The following block of code has to be executed atomically
         */
        spin_lock_irqsave(&irq_controller_lock,flags);
        p = &irq_desc[irq].action;
        if ((old = *p) != NULL) {
                /* Can't share interrupts unless both agree to */
                if (!(old->flags & new->flags & SA_SHIRQ)) {
                        spin_unlock_irqrestore(&irq_controller_lock,flags);
                        return -EBUSY;
                }

                /* add new interrupt at end of irq queue */
                do {
                        p = &old->next;
                        old = *p;
                } while (old);
                shared = 1;
        }

        *p = new;

        if (!shared) {
                irq_desc[irq].depth = 0;
                irq_desc[irq].status &= ~IRQ_DISABLED;
                irq_desc[irq].handler->startup(irq);
        }
        spin_unlock_irqrestore(&irq_controller_lock,flags);
        return 0;
}