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1da177e4 LT |
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 | ||
13 | /* | |
14 | * Autodetection depends on the fact that any interrupt that | |
15 | * comes in on to an unassigned handler will get stuck with | |
16 | * "IRQ_WAITING" cleared and the interrupt disabled. | |
17 | */ | |
18 | static DECLARE_MUTEX(probe_sem); | |
19 | ||
20 | /** | |
21 | * probe_irq_on - begin an interrupt autodetect | |
22 | * | |
23 | * Commence probing for an interrupt. The interrupts are scanned | |
24 | * and a mask of potential interrupt lines is returned. | |
25 | * | |
26 | */ | |
27 | unsigned long probe_irq_on(void) | |
28 | { | |
29 | unsigned long val, delay; | |
30 | irq_desc_t *desc; | |
31 | unsigned int i; | |
32 | ||
33 | down(&probe_sem); | |
34 | /* | |
35 | * something may have generated an irq long ago and we want to | |
36 | * flush such a longstanding irq before considering it as spurious. | |
37 | */ | |
38 | for (i = NR_IRQS-1; i > 0; i--) { | |
39 | desc = irq_desc + i; | |
40 | ||
41 | spin_lock_irq(&desc->lock); | |
42 | if (!irq_desc[i].action) | |
43 | irq_desc[i].handler->startup(i); | |
44 | spin_unlock_irq(&desc->lock); | |
45 | } | |
46 | ||
47 | /* Wait for longstanding interrupts to trigger. */ | |
48 | for (delay = jiffies + HZ/50; time_after(delay, jiffies); ) | |
49 | /* about 20ms delay */ barrier(); | |
50 | ||
51 | /* | |
52 | * enable any unassigned irqs | |
53 | * (we must startup again here because if a longstanding irq | |
54 | * happened in the previous stage, it may have masked itself) | |
55 | */ | |
56 | for (i = NR_IRQS-1; i > 0; i--) { | |
57 | desc = irq_desc + i; | |
58 | ||
59 | spin_lock_irq(&desc->lock); | |
60 | if (!desc->action) { | |
61 | desc->status |= IRQ_AUTODETECT | IRQ_WAITING; | |
62 | if (desc->handler->startup(i)) | |
63 | desc->status |= IRQ_PENDING; | |
64 | } | |
65 | spin_unlock_irq(&desc->lock); | |
66 | } | |
67 | ||
68 | /* | |
69 | * Wait for spurious interrupts to trigger | |
70 | */ | |
71 | for (delay = jiffies + HZ/10; time_after(delay, jiffies); ) | |
72 | /* about 100ms delay */ barrier(); | |
73 | ||
74 | /* | |
75 | * Now filter out any obviously spurious interrupts | |
76 | */ | |
77 | val = 0; | |
78 | for (i = 0; i < NR_IRQS; i++) { | |
79 | irq_desc_t *desc = irq_desc + i; | |
80 | unsigned int status; | |
81 | ||
82 | spin_lock_irq(&desc->lock); | |
83 | status = desc->status; | |
84 | ||
85 | if (status & IRQ_AUTODETECT) { | |
86 | /* It triggered already - consider it spurious. */ | |
87 | if (!(status & IRQ_WAITING)) { | |
88 | desc->status = status & ~IRQ_AUTODETECT; | |
89 | desc->handler->shutdown(i); | |
90 | } else | |
91 | if (i < 32) | |
92 | val |= 1 << i; | |
93 | } | |
94 | spin_unlock_irq(&desc->lock); | |
95 | } | |
96 | ||
97 | return val; | |
98 | } | |
99 | ||
100 | EXPORT_SYMBOL(probe_irq_on); | |
101 | ||
102 | /** | |
103 | * probe_irq_mask - scan a bitmap of interrupt lines | |
104 | * @val: mask of interrupts to consider | |
105 | * | |
106 | * Scan the interrupt lines and return a bitmap of active | |
107 | * autodetect interrupts. The interrupt probe logic state | |
108 | * is then returned to its previous value. | |
109 | * | |
110 | * Note: we need to scan all the irq's even though we will | |
111 | * only return autodetect irq numbers - just so that we reset | |
112 | * them all to a known state. | |
113 | */ | |
114 | unsigned int probe_irq_mask(unsigned long val) | |
115 | { | |
116 | unsigned int mask; | |
117 | int i; | |
118 | ||
119 | mask = 0; | |
120 | for (i = 0; i < NR_IRQS; i++) { | |
121 | irq_desc_t *desc = irq_desc + i; | |
122 | unsigned int status; | |
123 | ||
124 | spin_lock_irq(&desc->lock); | |
125 | status = desc->status; | |
126 | ||
127 | if (status & IRQ_AUTODETECT) { | |
128 | if (i < 16 && !(status & IRQ_WAITING)) | |
129 | mask |= 1 << i; | |
130 | ||
131 | desc->status = status & ~IRQ_AUTODETECT; | |
132 | desc->handler->shutdown(i); | |
133 | } | |
134 | spin_unlock_irq(&desc->lock); | |
135 | } | |
136 | up(&probe_sem); | |
137 | ||
138 | return mask & val; | |
139 | } | |
140 | EXPORT_SYMBOL(probe_irq_mask); | |
141 | ||
142 | /** | |
143 | * probe_irq_off - end an interrupt autodetect | |
144 | * @val: mask of potential interrupts (unused) | |
145 | * | |
146 | * Scans the unused interrupt lines and returns the line which | |
147 | * appears to have triggered the interrupt. If no interrupt was | |
148 | * found then zero is returned. If more than one interrupt is | |
149 | * found then minus the first candidate is returned to indicate | |
150 | * their is doubt. | |
151 | * | |
152 | * The interrupt probe logic state is returned to its previous | |
153 | * value. | |
154 | * | |
155 | * BUGS: When used in a module (which arguably shouldn't happen) | |
156 | * nothing prevents two IRQ probe callers from overlapping. The | |
157 | * results of this are non-optimal. | |
158 | */ | |
159 | int probe_irq_off(unsigned long val) | |
160 | { | |
161 | int i, irq_found = 0, nr_irqs = 0; | |
162 | ||
163 | for (i = 0; i < NR_IRQS; i++) { | |
164 | irq_desc_t *desc = irq_desc + i; | |
165 | unsigned int status; | |
166 | ||
167 | spin_lock_irq(&desc->lock); | |
168 | status = desc->status; | |
169 | ||
170 | if (status & IRQ_AUTODETECT) { | |
171 | if (!(status & IRQ_WAITING)) { | |
172 | if (!nr_irqs) | |
173 | irq_found = i; | |
174 | nr_irqs++; | |
175 | } | |
176 | desc->status = status & ~IRQ_AUTODETECT; | |
177 | desc->handler->shutdown(i); | |
178 | } | |
179 | spin_unlock_irq(&desc->lock); | |
180 | } | |
181 | up(&probe_sem); | |
182 | ||
183 | if (nr_irqs > 1) | |
184 | irq_found = -irq_found; | |
185 | return irq_found; | |
186 | } | |
187 | ||
188 | EXPORT_SYMBOL(probe_irq_off); | |
189 |