err.no Git - linux-2.6/blob - arch/arm26/kernel/irq.c

   1 /*
   2  *  linux/arch/arm/kernel/irq.c
   3  *
   4  *  Copyright (C) 1992 Linus Torvalds
   5  *  Modifications for ARM processor Copyright (C) 1995-2000 Russell King.
   6  *  'Borrowed' for ARM26 and (C) 2003 Ian Molton.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  *
  12  *  This file contains the code used by various IRQ handling routines:
  13  *  asking for different IRQ's should be done through these routines
  14  *  instead of just grabbing them. Thus setups with different IRQ numbers
  15  *  shouldn't result in any weird surprises, and installing new handlers
  16  *  should be easier.
  17  *
  18  *  IRQ's are in fact implemented a bit like signal handlers for the kernel.
  19  *  Naturally it's not a 1:1 relation, but there are similarities.
  20  */
  21 #include <linux/module.h>
  22 #include <linux/ptrace.h>
  23 #include <linux/kernel_stat.h>
  24 #include <linux/signal.h>
  25 #include <linux/sched.h>
  26 #include <linux/ioport.h>
  27 #include <linux/interrupt.h>
  28 #include <linux/slab.h>
  29 #include <linux/random.h>
  30 #include <linux/smp.h>
  31 #include <linux/init.h>
  32 #include <linux/seq_file.h>
  33 #include <linux/errno.h>
  34
  35 #include <asm/irq.h>
  36 #include <asm/system.h>
  37 #include <asm/irqchip.h>
  38
  39 //FIXME - this ought to be in a header IMO
  40 void __init arc_init_irq(void);
  41
  42 /*
  43  * Maximum IRQ count.  Currently, this is arbitary.  However, it should
  44  * not be set too low to prevent false triggering.  Conversely, if it
  45  * is set too high, then you could miss a stuck IRQ.
  46  *
  47  * FIXME Maybe we ought to set a timer and re-enable the IRQ at a later time?
  48  */
  49 #define MAX_IRQ_CNT     100000
  50
  51 static volatile unsigned long irq_err_count;
  52 static DEFINE_SPINLOCK(irq_controller_lock);
  53
  54 struct irqdesc irq_desc[NR_IRQS];
  55
  56 /*
  57  * Dummy mask/unmask handler
  58  */
  59 void dummy_mask_unmask_irq(unsigned int irq)
  60 {
  61 }
  62
  63 void do_bad_IRQ(unsigned int irq, struct irqdesc *desc, struct pt_regs *regs)
  64 {
  65         irq_err_count += 1;
  66         printk(KERN_ERR "IRQ: spurious interrupt %d\n", irq);
  67 }
  68
  69 static struct irqchip bad_chip = {
  70         .ack    = dummy_mask_unmask_irq,
  71         .mask   = dummy_mask_unmask_irq,
  72         .unmask = dummy_mask_unmask_irq,
  73 };
  74
  75 static struct irqdesc bad_irq_desc = {
  76         .chip   = &bad_chip,
  77         .handle = do_bad_IRQ,
  78         .depth  = 1,
  79 };
  80
  81 /**
  82  *      disable_irq - disable an irq and wait for completion
  83  *      @irq: Interrupt to disable
  84  *
  85  *      Disable the selected interrupt line.  We do this lazily.
  86  *
  87  *      This function may be called from IRQ context.
  88  */
  89 void disable_irq(unsigned int irq)
  90 {
  91         struct irqdesc *desc = irq_desc + irq;
  92         unsigned long flags;
  93         spin_lock_irqsave(&irq_controller_lock, flags);
  94         if (!desc->depth++)
  95                 desc->enabled = 0;
  96         spin_unlock_irqrestore(&irq_controller_lock, flags);
  97 }
  98 EXPORT_SYMBOL(disable_irq);
  99
 100 void disable_irq_nosync(unsigned int irq) __attribute__((alias("disable_irq")));
 101
 102 EXPORT_SYMBOL(disable_irq_nosync);
 103
 104 /**
 105  *      enable_irq - enable interrupt handling on an irq
 106  *      @irq: Interrupt to enable
 107  *
 108  *      Re-enables the processing of interrupts on this IRQ line.
 109  *      Note that this may call the interrupt handler, so you may
 110  *      get unexpected results if you hold IRQs disabled.
 111  *
 112  *      This function may be called from IRQ context.
 113  */
 114 void enable_irq(unsigned int irq)
 115 {
 116         struct irqdesc *desc = irq_desc + irq;
 117         unsigned long flags;
 118         int pending = 0;
 119
 120         spin_lock_irqsave(&irq_controller_lock, flags);
 121         if (unlikely(!desc->depth)) {
 122                 printk("enable_irq(%u) unbalanced from %p\n", irq,
 123                         __builtin_return_address(0)); //FIXME bum addresses reported - why?
 124         } else if (!--desc->depth) {
 125                 desc->probing = 0;
 126                 desc->enabled = 1;
 127                 desc->chip->unmask(irq);
 128                 pending = desc->pending;
 129                 desc->pending = 0;
 130                 /*
 131                  * If the interrupt was waiting to be processed,
 132                  * retrigger it.
 133                  */
 134                 if (pending)
 135                         desc->chip->rerun(irq);
 136         }
 137         spin_unlock_irqrestore(&irq_controller_lock, flags);
 138 }
 139 EXPORT_SYMBOL(enable_irq);
 140
 141 int show_interrupts(struct seq_file *p, void *v)
 142 {
 143         int i = *(loff_t *) v;
 144         struct irqaction * action;
 145
 146         if (i < NR_IRQS) {
 147                 action = irq_desc[i].action;
 148                 if (!action)
 149                         goto out;
 150                 seq_printf(p, "%3d: %10u ", i, kstat_irqs(i));
 151                 seq_printf(p, "  %s", action->name);
 152                 for (action = action->next; action; action = action->next) {
 153                         seq_printf(p, ", %s", action->name);
 154                 }
 155                 seq_putc(p, '\n');
 156         } else if (i == NR_IRQS) {
 157                 show_fiq_list(p, v);
 158                 seq_printf(p, "Err: %10lu\n", irq_err_count);
 159         }
 160 out:
 161         return 0;
 162 }
 163
 164 /*
 165  * IRQ lock detection.
 166  *
 167  * Hopefully, this should get us out of a few locked situations.
 168  * However, it may take a while for this to happen, since we need
 169  * a large number if IRQs to appear in the same jiffie with the
 170  * same instruction pointer (or within 2 instructions).
 171  */
 172 static int check_irq_lock(struct irqdesc *desc, int irq, struct pt_regs *regs)
 173 {
 174         unsigned long instr_ptr = instruction_pointer(regs);
 175
 176         if (desc->lck_jif == jiffies &&
 177             desc->lck_pc >= instr_ptr && desc->lck_pc < instr_ptr + 8) {
 178                 desc->lck_cnt += 1;
 179
 180                 if (desc->lck_cnt > MAX_IRQ_CNT) {
 181                         printk(KERN_ERR "IRQ LOCK: IRQ%d is locking the system, disabled\n", irq);
 182                         return 1;
 183                 }
 184         } else {
 185                 desc->lck_cnt = 0;
 186                 desc->lck_pc  = instruction_pointer(regs);
 187                 desc->lck_jif = jiffies;
 188         }
 189         return 0;
 190 }
 191
 192 static void
 193 __do_irq(unsigned int irq, struct irqaction *action, struct pt_regs *regs)
 194 {
 195         unsigned int status;
 196         int ret;
 197
 198         spin_unlock(&irq_controller_lock);
 199         if (!(action->flags & IRQF_DISABLED))
 200                 local_irq_enable();
 201
 202         status = 0;
 203         do {
 204                 ret = action->handler(irq, action->dev_id, regs);
 205                 if (ret == IRQ_HANDLED)
 206                         status |= action->flags;
 207                 action = action->next;
 208         } while (action);
 209
 210         if (status & IRQF_SAMPLE_RANDOM)
 211                 add_interrupt_randomness(irq);
 212
 213         spin_lock_irq(&irq_controller_lock);
 214 }
 215
 216 /*
 217  * This is for software-decoded IRQs.  The caller is expected to
 218  * handle the ack, clear, mask and unmask issues.
 219  */
 220 void
 221 do_simple_IRQ(unsigned int irq, struct irqdesc *desc, struct pt_regs *regs)
 222 {
 223         struct irqaction *action;
 224         const int cpu = smp_processor_id();
 225
 226         desc->triggered = 1;
 227
 228         kstat_cpu(cpu).irqs[irq]++;
 229
 230         action = desc->action;
 231         if (action)
 232                 __do_irq(irq, desc->action, regs);
 233 }
 234
 235 /*
 236  * Most edge-triggered IRQ implementations seem to take a broken
 237  * approach to this.  Hence the complexity.
 238  */
 239 void
 240 do_edge_IRQ(unsigned int irq, struct irqdesc *desc, struct pt_regs *regs)
 241 {
 242         const int cpu = smp_processor_id();
 243
 244         desc->triggered = 1;
 245
 246         /*
 247          * If we're currently running this IRQ, or its disabled,
 248          * we shouldn't process the IRQ.  Instead, turn on the
 249          * hardware masks.
 250          */
 251         if (unlikely(desc->running || !desc->enabled))
 252                 goto running;
 253
 254         /*
 255          * Acknowledge and clear the IRQ, but don't mask it.
 256          */
 257         desc->chip->ack(irq);
 258
 259         /*
 260          * Mark the IRQ currently in progress.
 261          */
 262         desc->running = 1;
 263
 264         kstat_cpu(cpu).irqs[irq]++;
 265
 266         do {
 267                 struct irqaction *action;
 268
 269                 action = desc->action;
 270                 if (!action)
 271                         break;
 272
 273                 if (desc->pending && desc->enabled) {
 274                         desc->pending = 0;
 275                         desc->chip->unmask(irq);
 276                 }
 277
 278                 __do_irq(irq, action, regs);
 279         } while (desc->pending);
 280
 281         desc->running = 0;
 282
 283         /*
 284          * If we were disabled or freed, shut down the handler.
 285          */
 286         if (likely(desc->action && !check_irq_lock(desc, irq, regs)))
 287                 return;
 288
 289  running:
 290         /*
 291          * We got another IRQ while this one was masked or
 292          * currently running.  Delay it.
 293          */
 294         desc->pending = 1;
 295         desc->chip->mask(irq);
 296         desc->chip->ack(irq);
 297 }
 298
 299 /*
 300  * Level-based IRQ handler.  Nice and simple.
 301  */
 302 void
 303 do_level_IRQ(unsigned int irq, struct irqdesc *desc, struct pt_regs *regs)
 304 {
 305         struct irqaction *action;
 306         const int cpu = smp_processor_id();
 307
 308         desc->triggered = 1;
 309
 310         /*
 311          * Acknowledge, clear _AND_ disable the interrupt.
 312          */
 313         desc->chip->ack(irq);
 314
 315         if (likely(desc->enabled)) {
 316                 kstat_cpu(cpu).irqs[irq]++;
 317
 318                 /*
 319                  * Return with this interrupt masked if no action
 320                  */
 321                 action = desc->action;
 322                 if (action) {
 323                         __do_irq(irq, desc->action, regs);
 324
 325                         if (likely(desc->enabled &&
 326                                    !check_irq_lock(desc, irq, regs)))
 327                                 desc->chip->unmask(irq);
 328                 }
 329         }
 330 }
 331
 332 /*
 333  * do_IRQ handles all hardware IRQ's.  Decoded IRQs should not
 334  * come via this function.  Instead, they should provide their
 335  * own 'handler'
 336  */
 337 asmlinkage void asm_do_IRQ(int irq, struct pt_regs *regs)
 338 {
 339         struct irqdesc *desc = irq_desc + irq;
 340
 341         /*
 342          * Some hardware gives randomly wrong interrupts.  Rather
 343          * than crashing, do something sensible.
 344          */
 345         if (irq >= NR_IRQS)
 346                 desc = &bad_irq_desc;
 347
 348         irq_enter();
 349         spin_lock(&irq_controller_lock);
 350         desc->handle(irq, desc, regs);
 351         spin_unlock(&irq_controller_lock);
 352         irq_exit();
 353 }
 354
 355 void __set_irq_handler(unsigned int irq, irq_handler_t handle, int is_chained)
 356 {
 357         struct irqdesc *desc;
 358         unsigned long flags;
 359
 360         if (irq >= NR_IRQS) {
 361                 printk(KERN_ERR "Trying to install handler for IRQ%d\n", irq);
 362                 return;
 363         }
 364
 365         if (handle == NULL)
 366                 handle = do_bad_IRQ;
 367
 368         desc = irq_desc + irq;
 369
 370         if (is_chained && desc->chip == &bad_chip)
 371                 printk(KERN_WARNING "Trying to install chained handler for IRQ%d\n", irq);
 372
 373         spin_lock_irqsave(&irq_controller_lock, flags);
 374         if (handle == do_bad_IRQ) {
 375                 desc->chip->mask(irq);
 376                 desc->chip->ack(irq);
 377                 desc->depth = 1;
 378                 desc->enabled = 0;
 379         }
 380         desc->handle = handle;
 381         if (handle != do_bad_IRQ && is_chained) {
 382                 desc->valid = 0;
 383                 desc->probe_ok = 0;
 384                 desc->depth = 0;
 385                 desc->chip->unmask(irq);
 386         }
 387         spin_unlock_irqrestore(&irq_controller_lock, flags);
 388 }
 389
 390 void set_irq_chip(unsigned int irq, struct irqchip *chip)
 391 {
 392         struct irqdesc *desc;
 393         unsigned long flags;
 394
 395         if (irq >= NR_IRQS) {
 396                 printk(KERN_ERR "Trying to install chip for IRQ%d\n", irq);
 397                 return;
 398         }
 399
 400         if (chip == NULL)
 401                 chip = &bad_chip;
 402
 403         desc = irq_desc + irq;
 404         spin_lock_irqsave(&irq_controller_lock, flags);
 405         desc->chip = chip;
 406         spin_unlock_irqrestore(&irq_controller_lock, flags);
 407 }
 408
 409 int set_irq_type(unsigned int irq, unsigned int type)
 410 {
 411         struct irqdesc *desc;
 412         unsigned long flags;
 413         int ret = -ENXIO;
 414
 415         if (irq >= NR_IRQS) {
 416                 printk(KERN_ERR "Trying to set irq type for IRQ%d\n", irq);
 417                 return -ENODEV;
 418         }
 419
 420         desc = irq_desc + irq;
 421         if (desc->chip->type) {
 422                 spin_lock_irqsave(&irq_controller_lock, flags);
 423                 ret = desc->chip->type(irq, type);
 424                 spin_unlock_irqrestore(&irq_controller_lock, flags);
 425         }
 426
 427         return ret;
 428 }
 429
 430 void set_irq_flags(unsigned int irq, unsigned int iflags)
 431 {
 432         struct irqdesc *desc;
 433         unsigned long flags;
 434
 435         if (irq >= NR_IRQS) {
 436                 printk(KERN_ERR "Trying to set irq flags for IRQ%d\n", irq);
 437                 return;
 438         }
 439
 440         desc = irq_desc + irq;
 441         spin_lock_irqsave(&irq_controller_lock, flags);
 442         desc->valid = (iflags & IRQF_VALID) != 0;
 443         desc->probe_ok = (iflags & IRQF_PROBE) != 0;
 444         desc->noautoenable = (iflags & IRQF_NOAUTOEN) != 0;
 445         spin_unlock_irqrestore(&irq_controller_lock, flags);
 446 }
 447
 448 int setup_irq(unsigned int irq, struct irqaction *new)
 449 {
 450         int shared = 0;
 451         struct irqaction *old, **p;
 452         unsigned long flags;
 453         struct irqdesc *desc;
 454
 455         /*
 456          * Some drivers like serial.c use request_irq() heavily,
 457          * so we have to be careful not to interfere with a
 458          * running system.
 459          */
 460         if (new->flags & IRQF_SAMPLE_RANDOM) {
 461                 /*
 462                  * This function might sleep, we want to call it first,
 463                  * outside of the atomic block.
 464                  * Yes, this might clear the entropy pool if the wrong
 465                  * driver is attempted to be loaded, without actually
 466                  * installing a new handler, but is this really a problem,
 467                  * only the sysadmin is able to do this.
 468                  */
 469                 rand_initialize_irq(irq);
 470         }
 471
 472         /*
 473          * The following block of code has to be executed atomically
 474          */
 475         desc = irq_desc + irq;
 476         spin_lock_irqsave(&irq_controller_lock, flags);
 477         p = &desc->action;
 478         if ((old = *p) != NULL) {
 479                 /* Can't share interrupts unless both agree to */
 480                 if (!(old->flags & new->flags & IRQF_SHARED)) {
 481                         spin_unlock_irqrestore(&irq_controller_lock, flags);
 482                         return -EBUSY;
 483                 }
 484
 485                 /* add new interrupt at end of irq queue */
 486                 do {
 487                         p = &old->next;
 488                         old = *p;
 489                 } while (old);
 490                 shared = 1;
 491         }
 492
 493         *p = new;
 494
 495         if (!shared) {
 496                 desc->probing = 0;
 497                 desc->running = 0;
 498                 desc->pending = 0;
 499                 desc->depth = 1;
 500                 if (!desc->noautoenable) {
 501                         desc->depth = 0;
 502                         desc->enabled = 1;
 503                         desc->chip->unmask(irq);
 504                 }
 505         }
 506
 507         spin_unlock_irqrestore(&irq_controller_lock, flags);
 508         return 0;
 509 }
 510
 511 /**
 512  *      request_irq - allocate an interrupt line
 513  *      @irq: Interrupt line to allocate
 514  *      @handler: Function to be called when the IRQ occurs
 515  *      @irqflags: Interrupt type flags
 516  *      @devname: An ascii name for the claiming device
 517  *      @dev_id: A cookie passed back to the handler function
 518  *
 519  *      This call allocates interrupt resources and enables the
 520  *      interrupt line and IRQ handling. From the point this
 521  *      call is made your handler function may be invoked. Since
 522  *      your handler function must clear any interrupt the board
 523  *      raises, you must take care both to initialise your hardware
 524  *      and to set up the interrupt handler in the right order.
 525  *
 526  *      Dev_id must be globally unique. Normally the address of the
 527  *      device data structure is used as the cookie. Since the handler
 528  *      receives this value it makes sense to use it.
 529  *
 530  *      If your interrupt is shared you must pass a non NULL dev_id
 531  *      as this is required when freeing the interrupt.
 532  *
 533  *      Flags:
 534  *
 535  *      IRQF_SHARED             Interrupt is shared
 536  *
 537  *      IRQF_DISABLED   Disable local interrupts while processing
 538  *
 539  *      IRQF_SAMPLE_RANDOM      The interrupt can be used for entropy
 540  *
 541  */
 542
 543 //FIXME - handler used to return void - whats the significance of the change?
 544 int request_irq(unsigned int irq, irqreturn_t (*handler)(int, void *, struct pt_regs *),
 545                  unsigned long irq_flags, const char * devname, void *dev_id)
 546 {
 547         unsigned long retval;
 548         struct irqaction *action;
 549
 550         if (irq >= NR_IRQS || !irq_desc[irq].valid || !handler ||
 551             (irq_flags & IRQF_SHARED && !dev_id))
 552                 return -EINVAL;
 553
 554         action = kmalloc(sizeof(struct irqaction), GFP_KERNEL);
 555         if (!action)
 556                 return -ENOMEM;
 557
 558         action->handler = handler;
 559         action->flags = irq_flags;
 560         cpus_clear(action->mask);
 561         action->name = devname;
 562         action->next = NULL;
 563         action->dev_id = dev_id;
 564
 565         retval = setup_irq(irq, action);
 566
 567         if (retval)
 568                 kfree(action);
 569         return retval;
 570 }
 571
 572 EXPORT_SYMBOL(request_irq);
 573
 574 /**
 575  *      free_irq - free an interrupt
 576  *      @irq: Interrupt line to free
 577  *      @dev_id: Device identity to free
 578  *
 579  *      Remove an interrupt handler. The handler is removed and if the
 580  *      interrupt line is no longer in use by any driver it is disabled.
 581  *      On a shared IRQ the caller must ensure the interrupt is disabled
 582  *      on the card it drives before calling this function.
 583  *
 584  *      This function may be called from interrupt context.
 585  */
 586 void free_irq(unsigned int irq, void *dev_id)
 587 {
 588         struct irqaction * action, **p;
 589         unsigned long flags;
 590
 591         if (irq >= NR_IRQS || !irq_desc[irq].valid) {
 592                 printk(KERN_ERR "Trying to free IRQ%d\n",irq);
 593 #ifdef CONFIG_DEBUG_ERRORS
 594                 __backtrace();
 595 #endif
 596                 return;
 597         }
 598
 599         spin_lock_irqsave(&irq_controller_lock, flags);
 600         for (p = &irq_desc[irq].action; (action = *p) != NULL; p = &action->next) {
 601                 if (action->dev_id != dev_id)
 602                         continue;
 603
 604                 /* Found it - now free it */
 605                 *p = action->next;
 606                 kfree(action);
 607                 goto out;
 608         }
 609         printk(KERN_ERR "Trying to free free IRQ%d\n",irq);
 610 #ifdef CONFIG_DEBUG_ERRORS
 611         __backtrace();
 612 #endif
 613 out:
 614         spin_unlock_irqrestore(&irq_controller_lock, flags);
 615 }
 616
 617 EXPORT_SYMBOL(free_irq);
 618
 619 /* Start the interrupt probing.  Unlike other architectures,
 620  * we don't return a mask of interrupts from probe_irq_on,
 621  * but return the number of interrupts enabled for the probe.
 622  * The interrupts which have been enabled for probing is
 623  * instead recorded in the irq_desc structure.
 624  */
 625 unsigned long probe_irq_on(void)
 626 {
 627         unsigned int i, irqs = 0;
 628         unsigned long delay;
 629
 630         /*
 631          * first snaffle up any unassigned but
 632          * probe-able interrupts
 633          */
 634         spin_lock_irq(&irq_controller_lock);
 635         for (i = 0; i < NR_IRQS; i++) {
 636                 if (!irq_desc[i].probe_ok || irq_desc[i].action)
 637                         continue;
 638
 639                 irq_desc[i].probing = 1;
 640                 irq_desc[i].triggered = 0;
 641                 if (irq_desc[i].chip->type)
 642                         irq_desc[i].chip->type(i, IRQT_PROBE);
 643                 irq_desc[i].chip->unmask(i);
 644                 irqs += 1;
 645         }
 646         spin_unlock_irq(&irq_controller_lock);
 647
 648         /*
 649          * wait for spurious interrupts to mask themselves out again
 650          */
 651         for (delay = jiffies + HZ/10; time_before(jiffies, delay); )
 652                 /* min 100ms delay */;
 653
 654         /*
 655          * now filter out any obviously spurious interrupts
 656          */
 657         spin_lock_irq(&irq_controller_lock);
 658         for (i = 0; i < NR_IRQS; i++) {
 659                 if (irq_desc[i].probing && irq_desc[i].triggered) {
 660                         irq_desc[i].probing = 0;
 661                         irqs -= 1;
 662                 }
 663         }
 664         spin_unlock_irq(&irq_controller_lock);
 665
 666         return irqs;
 667 }
 668
 669 EXPORT_SYMBOL(probe_irq_on);
 670
 671 /*
 672  * Possible return values:
 673  *  >= 0 - interrupt number
 674  *    -1 - no interrupt/many interrupts
 675  */
 676 int probe_irq_off(unsigned long irqs)
 677 {
 678         unsigned int i;
 679         int irq_found = NO_IRQ;
 680
 681         /*
 682          * look at the interrupts, and find exactly one
 683          * that we were probing has been triggered
 684          */
 685         spin_lock_irq(&irq_controller_lock);
 686         for (i = 0; i < NR_IRQS; i++) {
 687                 if (irq_desc[i].probing &&
 688                     irq_desc[i].triggered) {
 689                         if (irq_found != NO_IRQ) {
 690                                 irq_found = NO_IRQ;
 691                                 goto out;
 692                         }
 693                         irq_found = i;
 694                 }
 695         }
 696
 697         if (irq_found == -1)
 698                 irq_found = NO_IRQ;
 699 out:
 700         spin_unlock_irq(&irq_controller_lock);
 701
 702         return irq_found;
 703 }
 704
 705 EXPORT_SYMBOL(probe_irq_off);
 706
 707 void __init init_irq_proc(void)
 708 {
 709 }
 710
 711 void __init init_IRQ(void)
 712 {
 713         struct irqdesc *desc;
 714         extern void init_dma(void);
 715         int irq;
 716
 717         for (irq = 0, desc = irq_desc; irq < NR_IRQS; irq++, desc++)
 718                 *desc = bad_irq_desc;
 719
 720         arc_init_irq();
 721         init_dma();
 722 }