kernel/irq/manage.c

   1 /*
   2  * linux/kernel/irq/manage.c
   3  *
   4  * Copyright (C) 1992, 1998-2006 Linus Torvalds, Ingo Molnar
   5  * Copyright (C) 2005-2006 Thomas Gleixner
   6  *
   7  * This file contains driver APIs to the irq subsystem.
   8  */
   9
  10 #include <linux/config.h>
  11 #include <linux/irq.h>
  12 #include <linux/module.h>
  13 #include <linux/random.h>
  14 #include <linux/interrupt.h>
  15
  16 #include "internals.h"
  17
  18 #ifdef CONFIG_SMP
  19
  20 /**
  21  *      synchronize_irq - wait for pending IRQ handlers (on other CPUs)
  22  *      @irq: interrupt number to wait for
  23  *
  24  *      This function waits for any pending IRQ handlers for this interrupt
  25  *      to complete before returning. If you use this function while
  26  *      holding a resource the IRQ handler may need you will deadlock.
  27  *
  28  *      This function may be called - with care - from IRQ context.
  29  */
  30 void synchronize_irq(unsigned int irq)
  31 {
  32         struct irq_desc *desc = irq_desc + irq;
  33
  34         if (irq >= NR_IRQS)
  35                 return;
  36
  37         while (desc->status & IRQ_INPROGRESS)
  38                 cpu_relax();
  39 }
  40 EXPORT_SYMBOL(synchronize_irq);
  41
  42 #endif
  43
  44 /**
  45  *      disable_irq_nosync - disable an irq without waiting
  46  *      @irq: Interrupt to disable
  47  *
  48  *      Disable the selected interrupt line.  Disables and Enables are
  49  *      nested.
  50  *      Unlike disable_irq(), this function does not ensure existing
  51  *      instances of the IRQ handler have completed before returning.
  52  *
  53  *      This function may be called from IRQ context.
  54  */
  55 void disable_irq_nosync(unsigned int irq)
  56 {
  57         struct irq_desc *desc = irq_desc + irq;
  58         unsigned long flags;
  59
  60         if (irq >= NR_IRQS)
  61                 return;
  62
  63         spin_lock_irqsave(&desc->lock, flags);
  64         if (!desc->depth++) {
  65                 desc->status |= IRQ_DISABLED;
  66                 desc->chip->disable(irq);
  67         }
  68         spin_unlock_irqrestore(&desc->lock, flags);
  69 }
  70 EXPORT_SYMBOL(disable_irq_nosync);
  71
  72 /**
  73  *      disable_irq - disable an irq and wait for completion
  74  *      @irq: Interrupt to disable
  75  *
  76  *      Disable the selected interrupt line.  Enables and Disables are
  77  *      nested.
  78  *      This function waits for any pending IRQ handlers for this interrupt
  79  *      to complete before returning. If you use this function while
  80  *      holding a resource the IRQ handler may need you will deadlock.
  81  *
  82  *      This function may be called - with care - from IRQ context.
  83  */
  84 void disable_irq(unsigned int irq)
  85 {
  86         struct irq_desc *desc = irq_desc + irq;
  87
  88         if (irq >= NR_IRQS)
  89                 return;
  90
  91         disable_irq_nosync(irq);
  92         if (desc->action)
  93                 synchronize_irq(irq);
  94 }
  95 EXPORT_SYMBOL(disable_irq);
  96
  97 /**
  98  *      enable_irq - enable handling of an irq
  99  *      @irq: Interrupt to enable
 100  *
 101  *      Undoes the effect of one call to disable_irq().  If this
 102  *      matches the last disable, processing of interrupts on this
 103  *      IRQ line is re-enabled.
 104  *
 105  *      This function may be called from IRQ context.
 106  */
 107 void enable_irq(unsigned int irq)
 108 {
 109         struct irq_desc *desc = irq_desc + irq;
 110         unsigned long flags;
 111
 112         if (irq >= NR_IRQS)
 113                 return;
 114
 115         spin_lock_irqsave(&desc->lock, flags);
 116         switch (desc->depth) {
 117         case 0:
 118                 printk(KERN_WARNING "Unablanced enable_irq(%d)\n", irq);
 119                 WARN_ON(1);
 120                 break;
 121         case 1: {
 122                 unsigned int status = desc->status & ~IRQ_DISABLED;
 123
 124                 /* Prevent probing on this irq: */
 125                 desc->status = status | IRQ_NOPROBE;
 126                 check_irq_resend(desc, irq);
 127                 /* fall-through */
 128         }
 129         default:
 130                 desc->depth--;
 131         }
 132         spin_unlock_irqrestore(&desc->lock, flags);
 133 }
 134 EXPORT_SYMBOL(enable_irq);
 135
 136 /*
 137  * Internal function that tells the architecture code whether a
 138  * particular irq has been exclusively allocated or is available
 139  * for driver use.
 140  */
 141 int can_request_irq(unsigned int irq, unsigned long irqflags)
 142 {
 143         struct irqaction *action;
 144
 145         if (irq >= NR_IRQS || irq_desc[irq].status & IRQ_NOREQUEST)
 146                 return 0;
 147
 148         action = irq_desc[irq].action;
 149         if (action)
 150                 if (irqflags & action->flags & SA_SHIRQ)
 151                         action = NULL;
 152
 153         return !action;
 154 }
 155
 156 /*
 157  * Internal function to register an irqaction - typically used to
 158  * allocate special interrupts that are part of the architecture.
 159  */
 160 int setup_irq(unsigned int irq, struct irqaction *new)
 161 {
 162         struct irq_desc *desc = irq_desc + irq;
 163         struct irqaction *old, **p;
 164         unsigned long flags;
 165         int shared = 0;
 166
 167         if (irq >= NR_IRQS)
 168                 return -EINVAL;
 169
 170         if (desc->chip == &no_irq_type)
 171                 return -ENOSYS;
 172         /*
 173          * Some drivers like serial.c use request_irq() heavily,
 174          * so we have to be careful not to interfere with a
 175          * running system.
 176          */
 177         if (new->flags & SA_SAMPLE_RANDOM) {
 178                 /*
 179                  * This function might sleep, we want to call it first,
 180                  * outside of the atomic block.
 181                  * Yes, this might clear the entropy pool if the wrong
 182                  * driver is attempted to be loaded, without actually
 183                  * installing a new handler, but is this really a problem,
 184                  * only the sysadmin is able to do this.
 185                  */
 186                 rand_initialize_irq(irq);
 187         }
 188
 189         /*
 190          * The following block of code has to be executed atomically
 191          */
 192         spin_lock_irqsave(&desc->lock, flags);
 193         p = &desc->action;
 194         old = *p;
 195         if (old) {
 196                 /* Can't share interrupts unless both agree to */
 197                 if (!(old->flags & new->flags & SA_SHIRQ))
 198                         goto mismatch;
 199
 200 #if defined(CONFIG_IRQ_PER_CPU) && defined(SA_PERCPU_IRQ)
 201                 /* All handlers must agree on per-cpuness */
 202                 if ((old->flags & IRQ_PER_CPU) != (new->flags & IRQ_PER_CPU))
 203                         goto mismatch;
 204 #endif
 205
 206                 /* add new interrupt at end of irq queue */
 207                 do {
 208                         p = &old->next;
 209                         old = *p;
 210                 } while (old);
 211                 shared = 1;
 212         }
 213
 214         *p = new;
 215 #if defined(CONFIG_IRQ_PER_CPU) && defined(SA_PERCPU_IRQ)
 216         if (new->flags & SA_PERCPU_IRQ)
 217                 desc->status |= IRQ_PER_CPU;
 218 #endif
 219         if (!shared) {
 220                 desc->status &= ~(IRQ_AUTODETECT | IRQ_WAITING |
 221                                   IRQ_INPROGRESS);
 222
 223                 if (!(desc->status & IRQ_NOAUTOEN)) {
 224                         desc->depth = 0;
 225                         desc->status &= ~IRQ_DISABLED;
 226                         if (desc->chip->startup)
 227                                 desc->chip->startup(irq);
 228                         else
 229                                 desc->chip->enable(irq);
 230                 }
 231         }
 232         spin_unlock_irqrestore(&desc->lock, flags);
 233
 234         new->irq = irq;
 235         register_irq_proc(irq);
 236         new->dir = NULL;
 237         register_handler_proc(irq, new);
 238
 239         return 0;
 240
 241 mismatch:
 242         spin_unlock_irqrestore(&desc->lock, flags);
 243         if (!(new->flags & SA_PROBEIRQ)) {
 244                 printk(KERN_ERR "%s: irq handler mismatch\n", __FUNCTION__);
 245                 dump_stack();
 246         }
 247         return -EBUSY;
 248 }
 249
 250 /**
 251  *      free_irq - free an interrupt
 252  *      @irq: Interrupt line to free
 253  *      @dev_id: Device identity to free
 254  *
 255  *      Remove an interrupt handler. The handler is removed and if the
 256  *      interrupt line is no longer in use by any driver it is disabled.
 257  *      On a shared IRQ the caller must ensure the interrupt is disabled
 258  *      on the card it drives before calling this function. The function
 259  *      does not return until any executing interrupts for this IRQ
 260  *      have completed.
 261  *
 262  *      This function must not be called from interrupt context.
 263  */
 264 void free_irq(unsigned int irq, void *dev_id)
 265 {
 266         struct irq_desc *desc;
 267         struct irqaction **p;
 268         unsigned long flags;
 269
 270         WARN_ON(in_interrupt());
 271         if (irq >= NR_IRQS)
 272                 return;
 273
 274         desc = irq_desc + irq;
 275         spin_lock_irqsave(&desc->lock, flags);
 276         p = &desc->action;
 277         for (;;) {
 278                 struct irqaction *action = *p;
 279
 280                 if (action) {
 281                         struct irqaction **pp = p;
 282
 283                         p = &action->next;
 284                         if (action->dev_id != dev_id)
 285                                 continue;
 286
 287                         /* Found it - now remove it from the list of entries */
 288                         *pp = action->next;
 289
 290                         /* Currently used only by UML, might disappear one day.*/
 291 #ifdef CONFIG_IRQ_RELEASE_METHOD
 292                         if (desc->chip->release)
 293                                 desc->chip->release(irq, dev_id);
 294 #endif
 295
 296                         if (!desc->action) {
 297                                 desc->status |= IRQ_DISABLED;
 298                                 if (desc->chip->shutdown)
 299                                         desc->chip->shutdown(irq);
 300                                 else
 301                                         desc->chip->disable(irq);
 302                         }
 303                         spin_unlock_irqrestore(&desc->lock, flags);
 304                         unregister_handler_proc(irq, action);
 305
 306                         /* Make sure it's not being used on another CPU */
 307                         synchronize_irq(irq);
 308                         kfree(action);
 309                         return;
 310                 }
 311                 printk(KERN_ERR "Trying to free free IRQ%d\n", irq);
 312                 spin_unlock_irqrestore(&desc->lock, flags);
 313                 return;
 314         }
 315 }
 316 EXPORT_SYMBOL(free_irq);
 317
 318 /**
 319  *      request_irq - allocate an interrupt line
 320  *      @irq: Interrupt line to allocate
 321  *      @handler: Function to be called when the IRQ occurs
 322  *      @irqflags: Interrupt type flags
 323  *      @devname: An ascii name for the claiming device
 324  *      @dev_id: A cookie passed back to the handler function
 325  *
 326  *      This call allocates interrupt resources and enables the
 327  *      interrupt line and IRQ handling. From the point this
 328  *      call is made your handler function may be invoked. Since
 329  *      your handler function must clear any interrupt the board
 330  *      raises, you must take care both to initialise your hardware
 331  *      and to set up the interrupt handler in the right order.
 332  *
 333  *      Dev_id must be globally unique. Normally the address of the
 334  *      device data structure is used as the cookie. Since the handler
 335  *      receives this value it makes sense to use it.
 336  *
 337  *      If your interrupt is shared you must pass a non NULL dev_id
 338  *      as this is required when freeing the interrupt.
 339  *
 340  *      Flags:
 341  *
 342  *      SA_SHIRQ                Interrupt is shared
 343  *      SA_INTERRUPT            Disable local interrupts while processing
 344  *      SA_SAMPLE_RANDOM        The interrupt can be used for entropy
 345  *
 346  */
 347 int request_irq(unsigned int irq,
 348                 irqreturn_t (*handler)(int, void *, struct pt_regs *),
 349                 unsigned long irqflags, const char *devname, void *dev_id)
 350 {
 351         struct irqaction *action;
 352         int retval;
 353
 354         /*
 355          * Sanity-check: shared interrupts must pass in a real dev-ID,
 356          * otherwise we'll have trouble later trying to figure out
 357          * which interrupt is which (messes up the interrupt freeing
 358          * logic etc).
 359          */
 360         if ((irqflags & SA_SHIRQ) && !dev_id)
 361                 return -EINVAL;
 362         if (irq >= NR_IRQS)
 363                 return -EINVAL;
 364         if (irq_desc[irq].status & IRQ_NOREQUEST)
 365                 return -EINVAL;
 366         if (!handler)
 367                 return -EINVAL;
 368
 369         action = kmalloc(sizeof(struct irqaction), GFP_ATOMIC);
 370         if (!action)
 371                 return -ENOMEM;
 372
 373         action->handler = handler;
 374         action->flags = irqflags;
 375         cpus_clear(action->mask);
 376         action->name = devname;
 377         action->next = NULL;
 378         action->dev_id = dev_id;
 379
 380         select_smp_affinity(irq);
 381
 382         retval = setup_irq(irq, action);
 383         if (retval)
 384                 kfree(action);
 385
 386         return retval;
 387 }
 388 EXPORT_SYMBOL(request_irq);
 389