kernel/irq/handle.c

   1 /*
   2  * linux/kernel/irq/handle.c
   3  *
   4  * Copyright (C) 1992, 1998-2004 Linus Torvalds, Ingo Molnar
   5  *
   6  * This file contains the core interrupt handling code.
   7  */
   8
   9 #include <linux/irq.h>
  10 #include <linux/module.h>
  11 #include <linux/random.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/kernel_stat.h>
  14
  15 #include "internals.h"
  16
  17 /*
  18  * Linux has a controller-independent interrupt architecture.
  19  * Every controller has a 'controller-template', that is used
  20  * by the main code to do the right thing. Each driver-visible
  21  * interrupt source is transparently wired to the appropriate
  22  * controller. Thus drivers need not be aware of the
  23  * interrupt-controller.
  24  *
  25  * The code is designed to be easily extended with new/different
  26  * interrupt controllers, without having to do assembly magic or
  27  * having to touch the generic code.
  28  *
  29  * Controller mappings for all interrupt sources:
  30  */
  31 irq_desc_t irq_desc[NR_IRQS] __cacheline_aligned = {
  32         [0 ... NR_IRQS-1] = {
  33                 .status = IRQ_DISABLED,
  34                 .chip = &no_irq_type,
  35                 .lock = SPIN_LOCK_UNLOCKED,
  36 #ifdef CONFIG_SMP
  37                 .affinity = CPU_MASK_ALL
  38 #endif
  39         }
  40 };
  41
  42 /*
  43  * Generic 'no controller' code
  44  */
  45 static void end_none(unsigned int irq) { }
  46 static void enable_none(unsigned int irq) { }
  47 static void disable_none(unsigned int irq) { }
  48 static void shutdown_none(unsigned int irq) { }
  49 static unsigned int startup_none(unsigned int irq) { return 0; }
  50
  51 static void ack_none(unsigned int irq)
  52 {
  53         /*
  54          * 'what should we do if we get a hw irq event on an illegal vector'.
  55          * each architecture has to answer this themself.
  56          */
  57         ack_bad_irq(irq);
  58 }
  59
  60 struct hw_interrupt_type no_irq_type = {
  61         .typename =     "none",
  62         .startup =      startup_none,
  63         .shutdown =     shutdown_none,
  64         .enable =       enable_none,
  65         .disable =      disable_none,
  66         .ack =          ack_none,
  67         .end =          end_none,
  68         .set_affinity = NULL
  69 };
  70
  71 /*
  72  * Special, empty irq handler:
  73  */
  74 irqreturn_t no_action(int cpl, void *dev_id, struct pt_regs *regs)
  75 {
  76         return IRQ_NONE;
  77 }
  78
  79 /*
  80  * Have got an event to handle:
  81  */
  82 irqreturn_t handle_IRQ_event(unsigned int irq, struct pt_regs *regs,
  83                              struct irqaction *action)
  84 {
  85         irqreturn_t ret, retval = IRQ_NONE;
  86         unsigned int status = 0;
  87
  88         if (!(action->flags & SA_INTERRUPT))
  89                 local_irq_enable();
  90
  91         do {
  92                 ret = action->handler(irq, action->dev_id, regs);
  93                 if (ret == IRQ_HANDLED)
  94                         status |= action->flags;
  95                 retval |= ret;
  96                 action = action->next;
  97         } while (action);
  98
  99         if (status & SA_SAMPLE_RANDOM)
 100                 add_interrupt_randomness(irq);
 101         local_irq_disable();
 102
 103         return retval;
 104 }
 105
 106 /*
 107  * do_IRQ handles all normal device IRQ's (the special
 108  * SMP cross-CPU interrupts have their own specific
 109  * handlers).
 110  */
 111 fastcall unsigned int __do_IRQ(unsigned int irq, struct pt_regs *regs)
 112 {
 113         irq_desc_t *desc = irq_desc + irq;
 114         struct irqaction *action;
 115         unsigned int status;
 116
 117         kstat_this_cpu.irqs[irq]++;
 118         if (CHECK_IRQ_PER_CPU(desc->status)) {
 119                 irqreturn_t action_ret;
 120
 121                 /*
 122                  * No locking required for CPU-local interrupts:
 123                  */
 124                 if (desc->chip->ack)
 125                         desc->chip->ack(irq);
 126                 action_ret = handle_IRQ_event(irq, regs, desc->action);
 127                 desc->chip->end(irq);
 128                 return 1;
 129         }
 130
 131         spin_lock(&desc->lock);
 132         if (desc->chip->ack)
 133                 desc->chip->ack(irq);
 134         /*
 135          * REPLAY is when Linux resends an IRQ that was dropped earlier
 136          * WAITING is used by probe to mark irqs that are being tested
 137          */
 138         status = desc->status & ~(IRQ_REPLAY | IRQ_WAITING);
 139         status |= IRQ_PENDING; /* we _want_ to handle it */
 140
 141         /*
 142          * If the IRQ is disabled for whatever reason, we cannot
 143          * use the action we have.
 144          */
 145         action = NULL;
 146         if (likely(!(status & (IRQ_DISABLED | IRQ_INPROGRESS)))) {
 147                 action = desc->action;
 148                 status &= ~IRQ_PENDING; /* we commit to handling */
 149                 status |= IRQ_INPROGRESS; /* we are handling it */
 150         }
 151         desc->status = status;
 152
 153         /*
 154          * If there is no IRQ handler or it was disabled, exit early.
 155          * Since we set PENDING, if another processor is handling
 156          * a different instance of this same irq, the other processor
 157          * will take care of it.
 158          */
 159         if (unlikely(!action))
 160                 goto out;
 161
 162         /*
 163          * Edge triggered interrupts need to remember
 164          * pending events.
 165          * This applies to any hw interrupts that allow a second
 166          * instance of the same irq to arrive while we are in do_IRQ
 167          * or in the handler. But the code here only handles the _second_
 168          * instance of the irq, not the third or fourth. So it is mostly
 169          * useful for irq hardware that does not mask cleanly in an
 170          * SMP environment.
 171          */
 172         for (;;) {
 173                 irqreturn_t action_ret;
 174
 175                 spin_unlock(&desc->lock);
 176
 177                 action_ret = handle_IRQ_event(irq, regs, action);
 178
 179                 spin_lock(&desc->lock);
 180                 if (!noirqdebug)
 181                         note_interrupt(irq, desc, action_ret, regs);
 182                 if (likely(!(desc->status & IRQ_PENDING)))
 183                         break;
 184                 desc->status &= ~IRQ_PENDING;
 185         }
 186         desc->status &= ~IRQ_INPROGRESS;
 187
 188 out:
 189         /*
 190          * The ->end() handler has to deal with interrupts which got
 191          * disabled while the handler was running.
 192          */
 193         desc->chip->end(irq);
 194         spin_unlock(&desc->lock);
 195
 196         return 1;
 197 }
 198