kernel/irq/autoprobe.c

   1 /*
   2  * linux/kernel/irq/autoprobe.c
   3  *
   4  * Copyright (C) 1992, 1998-2004 Linus Torvalds, Ingo Molnar
   5  *
   6  * This file contains the interrupt probing code and driver APIs.
   7  */
   8
   9 #include <linux/irq.h>
  10 #include <linux/module.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/delay.h>
  13
  14 /*
  15  * Autodetection depends on the fact that any interrupt that
  16  * comes in on to an unassigned handler will get stuck with
  17  * "IRQ_WAITING" cleared and the interrupt disabled.
  18  */
  19 static DEFINE_MUTEX(probing_active);
  20
  21 /**
  22  *      probe_irq_on    - begin an interrupt autodetect
  23  *
  24  *      Commence probing for an interrupt. The interrupts are scanned
  25  *      and a mask of potential interrupt lines is returned.
  26  *
  27  */
  28 unsigned long probe_irq_on(void)
  29 {
  30         struct irq_desc *desc;
  31         unsigned long mask;
  32         unsigned int i;
  33
  34         mutex_lock(&probing_active);
  35         /*
  36          * something may have generated an irq long ago and we want to
  37          * flush such a longstanding irq before considering it as spurious.
  38          */
  39         for (i = NR_IRQS-1; i > 0; i--) {
  40                 desc = irq_desc + i;
  41
  42                 spin_lock_irq(&desc->lock);
  43                 if (!desc->action && !(desc->status & IRQ_NOPROBE)) {
  44                         /*
  45                          * Some chips need to know about probing in
  46                          * progress:
  47                          */
  48                         if (desc->chip->set_type)
  49                                 desc->chip->set_type(i, IRQ_TYPE_PROBE);
  50                         desc->chip->startup(i);
  51                 }
  52                 spin_unlock_irq(&desc->lock);
  53         }
  54
  55         /* Wait for longstanding interrupts to trigger. */
  56         msleep(20);
  57
  58         /*
  59          * enable any unassigned irqs
  60          * (we must startup again here because if a longstanding irq
  61          * happened in the previous stage, it may have masked itself)
  62          */
  63         for (i = NR_IRQS-1; i > 0; i--) {
  64                 desc = irq_desc + i;
  65
  66                 spin_lock_irq(&desc->lock);
  67                 if (!desc->action && !(desc->status & IRQ_NOPROBE)) {
  68                         desc->status |= IRQ_AUTODETECT | IRQ_WAITING;
  69                         if (desc->chip->startup(i))
  70                                 desc->status |= IRQ_PENDING;
  71                 }
  72                 spin_unlock_irq(&desc->lock);
  73         }
  74
  75         /*
  76          * Wait for spurious interrupts to trigger
  77          */
  78         msleep(100);
  79
  80         /*
  81          * Now filter out any obviously spurious interrupts
  82          */
  83         mask = 0;
  84         for (i = 0; i < NR_IRQS; i++) {
  85                 unsigned int status;
  86
  87                 desc = irq_desc + i;
  88                 spin_lock_irq(&desc->lock);
  89                 status = desc->status;
  90
  91                 if (status & IRQ_AUTODETECT) {
  92                         /* It triggered already - consider it spurious. */
  93                         if (!(status & IRQ_WAITING)) {
  94                                 desc->status = status & ~IRQ_AUTODETECT;
  95                                 desc->chip->shutdown(i);
  96                         } else
  97                                 if (i < 32)
  98                                         mask |= 1 << i;
  99                 }
 100                 spin_unlock_irq(&desc->lock);
 101         }
 102
 103         return mask;
 104 }
 105 EXPORT_SYMBOL(probe_irq_on);
 106
 107 /**
 108  *      probe_irq_mask - scan a bitmap of interrupt lines
 109  *      @val:   mask of interrupts to consider
 110  *
 111  *      Scan the interrupt lines and return a bitmap of active
 112  *      autodetect interrupts. The interrupt probe logic state
 113  *      is then returned to its previous value.
 114  *
 115  *      Note: we need to scan all the irq's even though we will
 116  *      only return autodetect irq numbers - just so that we reset
 117  *      them all to a known state.
 118  */
 119 unsigned int probe_irq_mask(unsigned long val)
 120 {
 121         unsigned int mask;
 122         int i;
 123
 124         mask = 0;
 125         for (i = 0; i < NR_IRQS; i++) {
 126                 struct irq_desc *desc = irq_desc + i;
 127                 unsigned int status;
 128
 129                 spin_lock_irq(&desc->lock);
 130                 status = desc->status;
 131
 132                 if (status & IRQ_AUTODETECT) {
 133                         if (i < 16 && !(status & IRQ_WAITING))
 134                                 mask |= 1 << i;
 135
 136                         desc->status = status & ~IRQ_AUTODETECT;
 137                         desc->chip->shutdown(i);
 138                 }
 139                 spin_unlock_irq(&desc->lock);
 140         }
 141         mutex_unlock(&probing_active);
 142
 143         return mask & val;
 144 }
 145 EXPORT_SYMBOL(probe_irq_mask);
 146
 147 /**
 148  *      probe_irq_off   - end an interrupt autodetect
 149  *      @val: mask of potential interrupts (unused)
 150  *
 151  *      Scans the unused interrupt lines and returns the line which
 152  *      appears to have triggered the interrupt. If no interrupt was
 153  *      found then zero is returned. If more than one interrupt is
 154  *      found then minus the first candidate is returned to indicate
 155  *      their is doubt.
 156  *
 157  *      The interrupt probe logic state is returned to its previous
 158  *      value.
 159  *
 160  *      BUGS: When used in a module (which arguably shouldn't happen)
 161  *      nothing prevents two IRQ probe callers from overlapping. The
 162  *      results of this are non-optimal.
 163  */
 164 int probe_irq_off(unsigned long val)
 165 {
 166         int i, irq_found = 0, nr_irqs = 0;
 167
 168         for (i = 0; i < NR_IRQS; i++) {
 169                 struct irq_desc *desc = irq_desc + i;
 170                 unsigned int status;
 171
 172                 spin_lock_irq(&desc->lock);
 173                 status = desc->status;
 174
 175                 if (status & IRQ_AUTODETECT) {
 176                         if (!(status & IRQ_WAITING)) {
 177                                 if (!nr_irqs)
 178                                         irq_found = i;
 179                                 nr_irqs++;
 180                         }
 181                         desc->status = status & ~IRQ_AUTODETECT;
 182                         desc->chip->shutdown(i);
 183                 }
 184                 spin_unlock_irq(&desc->lock);
 185         }
 186         mutex_unlock(&probing_active);
 187
 188         if (nr_irqs > 1)
 189                 irq_found = -irq_found;
 190
 191         return irq_found;
 192 }
 193 EXPORT_SYMBOL(probe_irq_off);
 194