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