aboutsummaryrefslogtreecommitdiffstats
path: root/arch/arm/kernel/irq.c
blob: 6f86d0af7c562f8e0211d0e209f3bfdc2814a18b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
/*
 *  linux/arch/arm/kernel/irq.c
 *
 *  Copyright (C) 1992 Linus Torvalds
 *  Modifications for ARM processor Copyright (C) 1995-2000 Russell King.
 *
 *  Support for Dynamic Tick Timer Copyright (C) 2004-2005 Nokia Corporation.
 *  Dynamic Tick Timer written by Tony Lindgren <tony@atomide.com> and
 *  Tuukka Tikkanen <tuukka.tikkanen@elektrobit.com>.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  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.
 *
 *  IRQ's 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/config.h>
#include <linux/kernel_stat.h>
#include <linux/module.h>
#include <linux/signal.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/ptrace.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/smp.h>
#include <linux/init.h>
#include <linux/seq_file.h>
#include <linux/errno.h>
#include <linux/list.h>
#include <linux/kallsyms.h>
#include <linux/proc_fs.h>

#include <asm/irq.h>
#include <asm/system.h>
#include <asm/mach/irq.h>
#include <asm/mach/time.h>

/*
 * Maximum IRQ count.  Currently, this is arbitary.  However, it should
 * not be set too low to prevent false triggering.  Conversely, if it
 * is set too high, then you could miss a stuck IRQ.
 *
 * Maybe we ought to set a timer and re-enable the IRQ at a later time?
 */
#define MAX_IRQ_CNT	100000

static int noirqdebug;
static volatile unsigned long irq_err_count;
static DEFINE_SPINLOCK(irq_controller_lock);
static LIST_HEAD(irq_pending);

struct irqdesc irq_desc[NR_IRQS];
void (*init_arch_irq)(void) __initdata = NULL;

/*
 * No architecture-specific irq_finish function defined in arm/arch/irqs.h.
 */
#ifndef irq_finish
#define irq_finish(irq) do { } while (0)
#endif

/*
 * Dummy mask/unmask handler
 */
void dummy_mask_unmask_irq(unsigned int irq)
{
}

irqreturn_t no_action(int irq, void *dev_id, struct pt_regs *regs)
{
	return IRQ_NONE;
}

void do_bad_IRQ(unsigned int irq, struct irqdesc *desc, struct pt_regs *regs)
{
	irq_err_count += 1;
	printk(KERN_ERR "IRQ: spurious interrupt %d\n", irq);
}

static struct irqchip bad_chip = {
	.ack	= dummy_mask_unmask_irq,
	.mask	= dummy_mask_unmask_irq,
	.unmask = dummy_mask_unmask_irq,
};

static struct irqdesc bad_irq_desc = {
	.chip		= &bad_chip,
	.handle		= do_bad_IRQ,
	.pend		= LIST_HEAD_INIT(bad_irq_desc.pend),
	.disable_depth	= 1,
};

#ifdef CONFIG_SMP
void synchronize_irq(unsigned int irq)
{
	struct irqdesc *desc = irq_desc + irq;

	while (desc->running)
		barrier();
}
EXPORT_SYMBOL(synchronize_irq);

#define smp_set_running(desc)	do { desc->running = 1; } while (0)
#define smp_clear_running(desc)	do { desc->running = 0; } while (0)
#else
#define smp_set_running(desc)	do { } while (0)
#define smp_clear_running(desc)	do { } while (0)
#endif

/**
 *	disable_irq_nosync - disable an irq without waiting
 *	@irq: Interrupt to disable
 *
 *	Disable the selected interrupt line.  Enables and disables
 *	are nested.  We do this lazily.
 *
 *	This function may be called from IRQ context.
 */
void disable_irq_nosync(unsigned int irq)
{
	struct irqdesc *desc = irq_desc + irq;
	unsigned long flags;

	spin_lock_irqsave(&irq_controller_lock, flags);
	desc->disable_depth++;
	list_del_init(&desc->pend);
	spin_unlock_irqrestore(&irq_controller_lock, flags);
}
EXPORT_SYMBOL(disable_irq_nosync);

/**
 *	disable_irq - disable an irq and wait for completion
 *	@irq: Interrupt to disable
 *
 *	Disable the selected interrupt line.  Enables and disables
 *	are nested.  This functions waits for any pending IRQ
 *	handlers for this interrupt to complete before returning.
 *	If you use this function while holding a resource the IRQ
 *	handler may need you will deadlock.
 *
 *	This function may be called - with care - from IRQ context.
 */
void disable_irq(unsigned int irq)
{
	struct irqdesc *desc = irq_desc + irq;

	disable_irq_nosync(irq);
	if (desc->action)
		synchronize_irq(irq);
}
EXPORT_SYMBOL(disable_irq);

/**
 *	enable_irq - enable interrupt handling on an irq
 *	@irq: Interrupt to enable
 *
 *	Re-enables the processing of interrupts on this IRQ line.
 *	Note that this may call the interrupt handler, so you may
 *	get unexpected results if you hold IRQs disabled.
 *
 *	This function may be called from IRQ context.
 */
void enable_irq(unsigned int irq)
{
	struct irqdesc *desc = irq_desc + irq;
	unsigned long flags;

	spin_lock_irqsave(&irq_controller_lock, flags);
	if (unlikely(!desc->disable_depth)) {
		printk("enable_irq(%u) unbalanced from %p\n", irq,
			__builtin_return_address(0));
	} else if (!--desc->disable_depth) {
		desc->probing = 0;
		desc->chip->unmask(irq);

		/*
		 * If the interrupt is waiting to be processed,
		 * try to re-run it.  We can't directly run it
		 * from here since the caller might be in an
		 * interrupt-protected region.
		 */
		if (desc->pending && list_empty(&desc->pend)) {
			desc->pending = 0;
			if (!desc->chip->retrigger ||
			    desc->chip->retrigger(irq))
				list_add(&desc->pend, &irq_pending);
		}
	}
	spin_unlock_irqrestore(&irq_controller_lock, flags);
}
EXPORT_SYMBOL(enable_irq);

/*
 * Enable wake on selected irq
 */
void enable_irq_wake(unsigned int irq)
{
	struct irqdesc *desc = irq_desc + irq;
	unsigned long flags;

	spin_lock_irqsave(&irq_controller_lock, flags);
	if (desc->chip->set_wake)
		desc->chip->set_wake(irq, 1);
	spin_unlock_irqrestore(&irq_controller_lock, flags);
}
EXPORT_SYMBOL(enable_irq_wake);

void disable_irq_wake(unsigned int irq)
{
	struct irqdesc *desc = irq_desc + irq;
	unsigned long flags;

	spin_lock_irqsave(&irq_controller_lock, flags);
	if (desc->chip->set_wake)
		desc->chip->set_wake(irq, 0);
	spin_unlock_irqrestore(&irq_controller_lock, flags);
}
EXPORT_SYMBOL(disable_irq_wake);

int show_interrupts(struct seq_file *p, void *v)
{
	int i = *(loff_t *) v, cpu;
	struct irqaction * action;
	unsigned long flags;

	if (i == 0) {
		char cpuname[12];

		seq_printf(p, "    ");
		for_each_present_cpu(cpu) {
			sprintf(cpuname, "CPU%d", cpu);
			seq_printf(p, " %10s", cpuname);
		}
		seq_putc(p, '\n');
	}

	if (i < NR_IRQS) {
		spin_lock_irqsave(&irq_controller_lock, flags);
	    	action = irq_desc[i].action;
		if (!action)
			goto unlock;

		seq_printf(p, "%3d: ", i);
		for_each_present_cpu(cpu)
			seq_printf(p, "%10u ", kstat_cpu(cpu).irqs[i]);
		seq_printf(p, "  %s", action->name);
		for (action = action->next; action; action = action->next)
			seq_printf(p, ", %s", action->name);

		seq_putc(p, '\n');
unlock:
		spin_unlock_irqrestore(&irq_controller_lock, flags);
	} else if (i == NR_IRQS) {
#ifdef CONFIG_ARCH_ACORN
		show_fiq_list(p, v);
#endif
#ifdef CONFIG_SMP
		show_ipi_list(p);
#endif
		seq_printf(p, "Err: %10lu\n", irq_err_count);
	}
	return 0;
}

/*
 * IRQ lock detection.
 *
 * Hopefully, this should get us out of a few locked situations.
 * However, it may take a while for this to happen, since we need
 * a large number if IRQs to appear in the same jiffie with the
 * same instruction pointer (or within 2 instructions).
 */
static int check_irq_lock(struct irqdesc *desc, int irq, struct pt_regs *regs)
{
	unsigned long instr_ptr = instruction_pointer(regs);

	if (desc->lck_jif == jiffies &&
	    desc->lck_pc >= instr_ptr && desc->lck_pc < instr_ptr + 8) {
		desc->lck_cnt += 1;

		if (desc->lck_cnt > MAX_IRQ_CNT) {
			printk(KERN_ERR "IRQ LOCK: IRQ%d is locking the system, disabled\n", irq);
			return 1;
		}
	} else {
		desc->lck_cnt = 0;
		desc->lck_pc  = instruction_pointer(regs);
		desc->lck_jif = jiffies;
	}
	return 0;
}

static void
report_bad_irq(unsigned int irq, struct pt_regs *regs, struct irqdesc *desc, int ret)
{
	static int count = 100;
	struct irqaction *action;

	if (!count || noirqdebug)
		return;

	count--;

	if (ret != IRQ_HANDLED && ret != IRQ_NONE) {
		printk("irq%u: bogus retval mask %x\n", irq, ret);
	} else {
		printk("irq%u: nobody cared\n", irq);
	}
	show_regs(regs);
	dump_stack();
	printk(KERN_ERR "handlers:");
	action = desc->action;
	do {
		printk("\n" KERN_ERR "[<%p>]", action->handler);
		print_symbol(" (%s)", (unsigned long)action->handler);
		action = action->next;
	} while (action);
	printk("\n");
}

static int
__do_irq(unsigned int irq, struct irqaction *action, struct pt_regs *regs)
{
	unsigned int status;
	int ret, retval = 0;

	spin_unlock(&irq_controller_lock);

#ifdef CONFIG_NO_IDLE_HZ
	if (!(action->flags & SA_TIMER) && system_timer->dyn_tick != NULL) {
		write_seqlock(&xtime_lock);
		if (system_timer->dyn_tick->state & DYN_TICK_ENABLED)
			system_timer->dyn_tick->handler(irq, 0, regs);
		write_sequnlock(&xtime_lock);
	}
#endif

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

	status = 0;
	do {
		ret = action->handler(irq, action->dev_id, regs);
		if (ret == IRQ_HANDLED)
			status |= action->flags;
		retval |= ret;
		action = action->next;
	} while (action);

	if (status & SA_SAMPLE_RANDOM)
		add_interrupt_randomness(irq);

	spin_lock_irq(&irq_controller_lock);

	return retval;
}

/*
 * This is for software-decoded IRQs.  The caller is expected to
 * handle the ack, clear, mask and unmask issues.
 */
void
do_simple_IRQ(unsigned int irq, struct irqdesc *desc, struct pt_regs *regs)
{
	struct irqaction *action;
	const unsigned int cpu = smp_processor_id();

	desc->triggered = 1;

	kstat_cpu(cpu).irqs[irq]++;

	smp_set_running(desc);

	action = desc->action;
	if (action) {
		int ret = __do_irq(irq, action, regs);
		if (ret != IRQ_HANDLED)
			report_bad_irq(irq, regs, desc, ret);
	}

	smp_clear_running(desc);
}

/*
 * Most edge-triggered IRQ implementations seem to take a broken
 * approach to this.  Hence the complexity.
 */
void
do_edge_IRQ(unsigned int irq, struct irqdesc *desc, struct pt_regs *regs)
{
	const unsigned int cpu = smp_processor_id();

	desc->triggered = 1;

	/*
	 * If we're currently running this IRQ, or its disabled,
	 * we shouldn't process the IRQ.  Instead, turn on the
	 * hardware masks.
	 */
	if (unlikely(desc->running || desc->disable_depth))
		goto running;

	/*
	 * Acknowledge and clear the IRQ, but don't mask it.
	 */
	desc->chip->ack(irq);

	/*
	 * Mark the IRQ currently in progress.
	 */
	desc->running = 1;

	kstat_cpu(cpu).irqs[irq]++;

	do {
		struct irqaction *action;

		action = desc->action;
		if (!action)
			break;

		if (desc->pending && !desc->disable_depth) {
			desc->pending = 0;
			desc->chip->unmask(irq);
		}

		__do_irq(irq, action, regs);
	} while (desc->pending && !desc->disable_depth);

	desc->running = 0;

	/*
	 * If we were disabled or freed, shut down the handler.
	 */
	if (likely(desc->action && !check_irq_lock(desc, irq, regs)))
		return;

 running:
	/*
	 * We got another IRQ while this one was masked or
	 * currently running.  Delay it.
	 */
	desc->pending = 1;
	desc->chip->mask(irq);
	desc->chip->ack(irq);
}

/*
 * Level-based IRQ handler.  Nice and simple.
 */
void
do_level_IRQ(unsigned int irq, struct irqdesc *desc, struct pt_regs *regs)
{
	struct irqaction *action;
	const unsigned int cpu = smp_processor_id();

	desc->triggered = 1;

	/*
	 * Acknowledge, clear _AND_ disable the interrupt.
	 */
	desc->chip->ack(irq);

	if (likely(!desc->disable_depth)) {
		kstat_cpu(cpu).irqs[irq]++;

		smp_set_running(desc);

		/*
		 * Return with this interrupt masked if no action
		 */
		action = desc->action;
		if (action) {
			int ret = __do_irq(irq, desc->action, regs);

			if (ret != IRQ_HANDLED)
				report_bad_irq(irq, regs, desc, ret);

			if (likely(!desc->disable_depth &&
				   !check_irq_lock(desc, irq, regs)))
				desc->chip->unmask(irq);
		}

		smp_clear_running(desc);
	}
}

static void do_pending_irqs(struct pt_regs *regs)
{
	struct list_head head, *l, *n;

	do {
		struct irqdesc *desc;

		/*
		 * First, take the pending interrupts off the list.
		 * The act of calling the handlers may add some IRQs
		 * back onto the list.
		 */
		head = irq_pending;
		INIT_LIST_HEAD(&irq_pending);
		head.next->prev = &head;
		head.prev->next = &head;

		/*
		 * Now run each entry.  We must delete it from our
		 * list before calling the handler.
		 */
		list_for_each_safe(l, n, &head) {
			desc = list_entry(l, struct irqdesc, pend);
			list_del_init(&desc->pend);
			desc_handle_irq(desc - irq_desc, desc, regs);
		}

		/*
		 * The list must be empty.
		 */
		BUG_ON(!list_empty(&head));
	} while (!list_empty(&irq_pending));
}

/*
 * do_IRQ handles all hardware IRQ's.  Decoded IRQs should not
 * come via this function.  Instead, they should provide their
 * own 'handler'
 */
asmlinkage void asm_do_IRQ(unsigned int irq, struct pt_regs *regs)
{
	struct irqdesc *desc = irq_desc + irq;

	/*
	 * Some hardware gives randomly wrong interrupts.  Rather
	 * than crashing, do something sensible.
	 */
	if (irq >= NR_IRQS)
		desc = &bad_irq_desc;

	irq_enter();
	spin_lock(&irq_controller_lock);
	desc_handle_irq(irq, desc, regs);

	/*
	 * Now re-run any pending interrupts.
	 */
	if (!list_empty(&irq_pending))
		do_pending_irqs(regs);

	irq_finish(irq);

	spin_unlock(&irq_controller_lock);
	irq_exit();
}

void __set_irq_handler(unsigned int irq, irq_handler_t handle, int is_chained)
{
	struct irqdesc *desc;
	unsigned long flags;

	if (irq >= NR_IRQS) {
		printk(KERN_ERR "Trying to install handler for IRQ%d\n", irq);
		return;
	}

	if (handle == NULL)
		handle = do_bad_IRQ;

	desc = irq_desc + irq;

	if (is_chained && desc->chip == &bad_chip)
		printk(KERN_WARNING "Trying to install chained handler for IRQ%d\n", irq);

	spin_lock_irqsave(&irq_controller_lock, flags);
	if (handle == do_bad_IRQ) {
		desc->chip->mask(irq);
		desc->chip->ack(irq);
		desc->disable_depth = 1;
	}
	desc->handle = handle;
	if (handle != do_bad_IRQ && is_chained) {
		desc->valid = 0;
		desc->probe_ok = 0;
		desc->disable_depth = 0;
		desc->chip->unmask(irq);
	}
	spin_unlock_irqrestore(&irq_controller_lock, flags);
}

void set_irq_chip(unsigned int irq, struct irqchip *chip)
{
	struct irqdesc *desc;
	unsigned long flags;

	if (irq >= NR_IRQS) {
		printk(KERN_ERR "Trying to install chip for IRQ%d\n", irq);
		return;
	}

	if (chip == NULL)
		chip = &bad_chip;

	desc = irq_desc + irq;
	spin_lock_irqsave(&irq_controller_lock, flags);
	desc->chip = chip;
	spin_unlock_irqrestore(&irq_controller_lock, flags);
}

int set_irq_type(unsigned int irq, unsigned int type)
{
	struct irqdesc *desc;
	unsigned long flags;
	int ret = -ENXIO;

	if (irq >= NR_IRQS) {
		printk(KERN_ERR "Trying to set irq type for IRQ%d\n", irq);
		return -ENODEV;
	}

	desc = irq_desc + irq;
	if (desc->chip->set_type) {
		spin_lock_irqsave(&irq_controller_lock, flags);
		ret = desc->chip->set_type(irq, type);
		spin_unlock_irqrestore(&irq_controller_lock, flags);
	}

	return ret;
}
EXPORT_SYMBOL(set_irq_type);

void set_irq_flags(unsigned int irq, unsigned int iflags)
{
	struct irqdesc *desc;
	unsigned long flags;

	if (irq >= NR_IRQS) {
		printk(KERN_ERR "Trying to set irq flags for IRQ%d\n", irq);
		return;
	}

	desc = irq_desc + irq;
	spin_lock_irqsave(&irq_controller_lock, flags);
	desc->valid = (iflags & IRQF_VALID) != 0;
	desc->probe_ok = (iflags & IRQF_PROBE) != 0;
	desc->noautoenable = (iflags & IRQF_NOAUTOEN) != 0;
	spin_unlock_irqrestore(&irq_controller_lock, flags);
}

int setup_irq(unsigned int irq, struct irqaction *new)
{
	int shared = 0;
	struct irqaction *old, **p;
	unsigned long flags;
	struct irqdesc *desc;

	/*
	 * 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
	 */
	desc = irq_desc + irq;
	spin_lock_irqsave(&irq_controller_lock, flags);
	p = &desc->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) {
 		desc->probing = 0;
		desc->running = 0;
		desc->pending = 0;
		desc->disable_depth = 1;
		if (!desc->noautoenable) {
			desc->disable_depth = 0;
			desc->chip->unmask(irq);
		}
	}

	spin_unlock_irqrestore(&irq_controller_lock, flags);
	return 0;
}

/**
 *	request_irq - allocate an interrupt line
 *	@irq: Interrupt line to allocate
 *	@handler: Function to be called when the IRQ occurs
 *	@irqflags: Interrupt type flags
 *	@devname: An ascii name for the claiming device
 *	@dev_id: A cookie passed back to the handler function
 *
 *	This call allocates interrupt resources and enables the
 *	interrupt line and IRQ handling. From the point this
 *	call is made your handler function may be invoked. Since
 *	your handler function must clear any interrupt the board
 *	raises, you must take care both to initialise your hardware
 *	and to set up the interrupt handler in the right order.
 *
 *	Dev_id must be globally unique. Normally the address of the
 *	device data structure is used as the cookie. Since the handler
 *	receives this value it makes sense to use it.
 *
 *	If your interrupt is shared you must pass a non NULL dev_id
 *	as this is required when freeing the interrupt.
 *
 *	Flags:
 *
 *	SA_SHIRQ		Interrupt is shared
 *
 *	SA_INTERRUPT		Disable local interrupts while processing
 *
 *	SA_SAMPLE_RANDOM	The interrupt can be used for entropy
 *
 */
int request_irq(unsigned int irq, irqreturn_t (*handler)(int, void *, struct pt_regs *),
		 unsigned long irq_flags, const char * devname, void *dev_id)
{
	unsigned long retval;
	struct irqaction *action;

	if (irq >= NR_IRQS || !irq_desc[irq].valid || !handler ||
	    (irq_flags & SA_SHIRQ && !dev_id))
		return -EINVAL;

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

	action->handler = handler;
	action->flags = irq_flags;
	cpus_clear(action->mask);
	action->name = devname;
	action->next = NULL;
	action->dev_id = dev_id;

	retval = setup_irq(irq, action);

	if (retval)
		kfree(action);
	return retval;
}

EXPORT_SYMBOL(request_irq);

/**
 *	free_irq - free an interrupt
 *	@irq: Interrupt line to free
 *	@dev_id: Device identity to free
 *
 *	Remove an interrupt handler. The handler is removed and if the
 *	interrupt line is no longer in use by any driver it is disabled.
 *	On a shared IRQ the caller must ensure the interrupt is disabled
 *	on the card it drives before calling this function.
 *
 *	This function must not be called from interrupt context.
 */
void free_irq(unsigned int irq, void *dev_id)
{
	struct irqaction * action, **p;
	unsigned long flags;

	if (irq >= NR_IRQS || !irq_desc[irq].valid) {
		printk(KERN_ERR "Trying to free IRQ%d\n",irq);
		dump_stack();
		return;
	}

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

	    	/* Found it - now free it */
		*p = action->next;
		break;
	}
	spin_unlock_irqrestore(&irq_controller_lock, flags);

	if (!action) {
		printk(KERN_ERR "Trying to free free IRQ%d\n",irq);
		dump_stack();
	} else {
		synchronize_irq(irq);
		kfree(action);
	}
}

EXPORT_SYMBOL(free_irq);

static DECLARE_MUTEX(probe_sem);

/* Start the interrupt probing.  Unlike other architectures,
 * we don't return a mask of interrupts from probe_irq_on,
 * but return the number of interrupts enabled for the probe.
 * The interrupts which have been enabled for probing is
 * instead recorded in the irq_desc structure.
 */
unsigned long probe_irq_on(void)
{
	unsigned int i, irqs = 0;
	unsigned long delay;

	down(&probe_sem);

	/*
	 * first snaffle up any unassigned but
	 * probe-able interrupts
	 */
	spin_lock_irq(&irq_controller_lock);
	for (i = 0; i < NR_IRQS; i++) {
		if (!irq_desc[i].probe_ok || irq_desc[i].action)
			continue;

		irq_desc[i].probing = 1;
		irq_desc[i].triggered = 0;
		if (irq_desc[i].chip->set_type)
			irq_desc[i].chip->set_type(i, IRQT_PROBE);
		irq_desc[i].chip->unmask(i);
		irqs += 1;
	}
	spin_unlock_irq(&irq_controller_lock);

	/*
	 * wait for spurious interrupts to mask themselves out again
	 */
	for (delay = jiffies + HZ/10; time_before(jiffies, delay); )
		/* min 100ms delay */;

	/*
	 * now filter out any obviously spurious interrupts
	 */
	spin_lock_irq(&irq_controller_lock);
	for (i = 0; i < NR_IRQS; i++) {
		if (irq_desc[i].probing && irq_desc[i].triggered) {
			irq_desc[i].probing = 0;
			irqs -= 1;
		}
	}
	spin_unlock_irq(&irq_controller_lock);

	return irqs;
}

EXPORT_SYMBOL(probe_irq_on);

unsigned int probe_irq_mask(unsigned long irqs)
{
	unsigned int mask = 0, i;

	spin_lock_irq(&irq_controller_lock);
	for (i = 0; i < 16 && i < NR_IRQS; i++)
		if (irq_desc[i].probing && irq_desc[i].triggered)
			mask |= 1 << i;
	spin_unlock_irq(&irq_controller_lock);

	up(&probe_sem);

	return mask;
}
EXPORT_SYMBOL(probe_irq_mask);

/*
 * Possible return values:
 *  >= 0 - interrupt number
 *    -1 - no interrupt/many interrupts
 */
int probe_irq_off(unsigned long irqs)
{
	unsigned int i;
	int irq_found = NO_IRQ;

	/*
	 * look at the interrupts, and find exactly one
	 * that we were probing has been triggered
	 */
	spin_lock_irq(&irq_controller_lock);
	for (i = 0; i < NR_IRQS; i++) {
		if (irq_desc[i].probing &&
		    irq_desc[i].triggered) {
			if (irq_found != NO_IRQ) {
				irq_found = NO_IRQ;
				goto out;
			}
			irq_found = i;
		}
	}

	if (irq_found == -1)
		irq_found = NO_IRQ;
out:
	spin_unlock_irq(&irq_controller_lock);

	up(&probe_sem);

	return irq_found;
}

EXPORT_SYMBOL(probe_irq_off);

#ifdef CONFIG_SMP
static void route_irq(struct irqdesc *desc, unsigned int irq, unsigned int cpu)
{
	pr_debug("IRQ%u: moving from cpu%u to cpu%u\n", irq, desc->cpu, cpu);

	spin_lock_irq(&irq_controller_lock);
	desc->cpu = cpu;
	desc->chip->set_cpu(desc, irq, cpu);
	spin_unlock_irq(&irq_controller_lock);
}

#ifdef CONFIG_PROC_FS
static int
irq_affinity_read_proc(char *page, char **start, off_t off, int count,
		       int *eof, void *data)
{
	struct irqdesc *desc = irq_desc + ((int)data);
	int len = cpumask_scnprintf(page, count, desc->affinity);

	if (count - len < 2)
		return -EINVAL;
	page[len++] = '\n';
	page[len] = '\0';

	return len;
}

static int
irq_affinity_write_proc(struct file *file, const char __user *buffer,
			unsigned long count, void *data)
{
	unsigned int irq = (unsigned int)data;
	struct irqdesc *desc = irq_desc + irq;
	cpumask_t affinity, tmp;
	int ret = -EIO;

	if (!desc->chip->set_cpu)
		goto out;

	ret = cpumask_parse(buffer, count, affinity);
	if (ret)
		goto out;

	cpus_and(tmp, affinity, cpu_online_map);
	if (cpus_empty(tmp)) {
		ret = -EINVAL;
		goto out;
	}

	desc->affinity = affinity;
	route_irq(desc, irq, first_cpu(tmp));
	ret = count;

 out:
	return ret;
}
#endif
#endif

void __init init_irq_proc(void)
{
#if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
	struct proc_dir_entry *dir;
	int irq;

	dir = proc_mkdir("irq", NULL);
	if (!dir)
		return;

	for (irq = 0; irq < NR_IRQS; irq++) {
		struct proc_dir_entry *entry;
		struct irqdesc *desc;
		char name[16];

		desc = irq_desc + irq;
		memset(name, 0, sizeof(name));
		snprintf(name, sizeof(name) - 1, "%u", irq);

		desc->procdir = proc_mkdir(name, dir);
		if (!desc->procdir)
			continue;

		entry = create_proc_entry("smp_affinity", 0600, desc->procdir);
		if (entry) {
			entry->nlink = 1;
			entry->data = (void *)irq;
			entry->read_proc = irq_affinity_read_proc;
			entry->write_proc = irq_affinity_write_proc;
		}
	}
#endif
}

void __init init_IRQ(void)
{
	struct irqdesc *desc;
	extern void init_dma(void);
	int irq;

#ifdef CONFIG_SMP
	bad_irq_desc.affinity = CPU_MASK_ALL;
	bad_irq_desc.cpu = smp_processor_id();
#endif

	for (irq = 0, desc = irq_desc; irq < NR_IRQS; irq++, desc++) {
		*desc = bad_irq_desc;
		INIT_LIST_HEAD(&desc->pend);
	}

	init_arch_irq();
	init_dma();
}

static int __init noirqdebug_setup(char *str)
{
	noirqdebug = 1;
	return 1;
}

__setup("noirqdebug", noirqdebug_setup);

#ifdef CONFIG_HOTPLUG_CPU
/*
 * The CPU has been marked offline.  Migrate IRQs off this CPU.  If
 * the affinity settings do not allow other CPUs, force them onto any
 * available CPU.
 */
void migrate_irqs(void)
{
	unsigned int i, cpu = smp_processor_id();

	for (i = 0; i < NR_IRQS; i++) {
		struct irqdesc *desc = irq_desc + i;

		if (desc->cpu == cpu) {
			unsigned int newcpu = any_online_cpu(desc->affinity);

			if (newcpu == NR_CPUS) {
				if (printk_ratelimit())
					printk(KERN_INFO "IRQ%u no longer affine to CPU%u\n",
					       i, cpu);

				cpus_setall(desc->affinity);
				newcpu = any_online_cpu(desc->affinity);
			}

			route_irq(desc, i, newcpu);
		}
	}
}
#endif /* CONFIG_HOTPLUG_CPU */