1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 1992, 1998-2004 Linus Torvalds, Ingo Molnar
4 *
5 * This file contains the interrupt probing code and driver APIs.
6 */
7
8 #include <linux/irq.h>
9 #include <linux/module.h>
10 #include <linux/interrupt.h>
11 #include <linux/delay.h>
12 #include <linux/async.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 * "IRQS_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 int i;
35
36 /*
37 * quiesce the kernel, or at least the asynchronous portion
38 */
39 async_synchronize_full();
40 mutex_lock(&probing_active);
41 /*
42 * something may have generated an irq long ago and we want to
43 * flush such a longstanding irq before considering it as spurious.
44 */
45 for_each_irq_desc_reverse(i, desc) {
46 raw_spin_lock_irq(&desc->lock);
47 if (!desc->action && irq_settings_can_probe(desc)) {
48 /*
49 * Some chips need to know about probing in
50 * progress:
51 */
52 if (desc->irq_data.chip->irq_set_type)
53 desc->irq_data.chip->irq_set_type(&desc->irq_data,
54 IRQ_TYPE_PROBE);
55 irq_activate_and_startup(desc, IRQ_NORESEND);
56 }
57 raw_spin_unlock_irq(&desc->lock);
58 }
59
60 /* Wait for longstanding interrupts to trigger. */
61 msleep(20);
62
63 /*
64 * enable any unassigned irqs
65 * (we must startup again here because if a longstanding irq
66 * happened in the previous stage, it may have masked itself)
67 */
68 for_each_irq_desc_reverse(i, desc) {
69 raw_spin_lock_irq(&desc->lock);
70 if (!desc->action && irq_settings_can_probe(desc)) {
71 desc->istate |= IRQS_AUTODETECT | IRQS_WAITING;
72 if (irq_activate_and_startup(desc, IRQ_NORESEND))
73 desc->istate |= IRQS_PENDING;
74 }
75 raw_spin_unlock_irq(&desc->lock);
76 }
77
78 /*
79 * Wait for spurious interrupts to trigger
80 */
81 msleep(100);
82
83 /*
84 * Now filter out any obviously spurious interrupts
85 */
86 for_each_irq_desc(i, desc) {
87 raw_spin_lock_irq(&desc->lock);
88
89 if (desc->istate & IRQS_AUTODETECT) {
90 /* It triggered already - consider it spurious. */
91 if (!(desc->istate & IRQS_WAITING)) {
92 desc->istate &= ~IRQS_AUTODETECT;
93 irq_shutdown_and_deactivate(desc);
94 } else
95 if (i < 32)
96 mask |= 1 << i;
97 }
98 raw_spin_unlock_irq(&desc->lock);
99 }
100
101 return mask;
102 }
103 EXPORT_SYMBOL(probe_irq_on);
104
105 /**
106 * probe_irq_mask - scan a bitmap of interrupt lines
107 * @val: mask of interrupts to consider
108 *
109 * Scan the interrupt lines and return a bitmap of active
110 * autodetect interrupts. The interrupt probe logic state
111 * is then returned to its previous value.
112 *
113 * Note: we need to scan all the irq's even though we will
114 * only return autodetect irq numbers - just so that we reset
115 * them all to a known state.
116 */
117 unsigned int probe_irq_mask(unsigned long val)
118 {
119 unsigned int mask = 0;
120 struct irq_desc *desc;
121 int i;
122
123 for_each_irq_desc(i, desc) {
124 raw_spin_lock_irq(&desc->lock);
125 if (desc->istate & IRQS_AUTODETECT) {
126 if (i < 16 && !(desc->istate & IRQS_WAITING))
127 mask |= 1 << i;
128
129 desc->istate &= ~IRQS_AUTODETECT;
130 irq_shutdown_and_deactivate(desc);
131 }
132 raw_spin_unlock_irq(&desc->lock);
133 }
134 mutex_unlock(&probing_active);
135
136 return mask & val;
137 }
138 EXPORT_SYMBOL(probe_irq_mask);
139
140 /**
141 * probe_irq_off - end an interrupt autodetect
142 * @val: mask of potential interrupts (unused)
143 *
144 * Scans the unused interrupt lines and returns the line which
145 * appears to have triggered the interrupt. If no interrupt was
146 * found then zero is returned. If more than one interrupt is
147 * found then minus the first candidate is returned to indicate
148 * their is doubt.
149 *
150 * The interrupt probe logic state is returned to its previous
151 * value.
152 *
153 * BUGS: When used in a module (which arguably shouldn't happen)
154 * nothing prevents two IRQ probe callers from overlapping. The
155 * results of this are non-optimal.
156 */
157 int probe_irq_off(unsigned long val)
158 {
159 int i, irq_found = 0, nr_of_irqs = 0;
160 struct irq_desc *desc;
161
162 for_each_irq_desc(i, desc) {
163 raw_spin_lock_irq(&desc->lock);
164
165 if (desc->istate & IRQS_AUTODETECT) {
166 if (!(desc->istate & IRQS_WAITING)) {
167 if (!nr_of_irqs)
168 irq_found = i;
169 nr_of_irqs++;
170 }
171 desc->istate &= ~IRQS_AUTODETECT;
172 irq_shutdown_and_deactivate(desc);
173 }
174 raw_spin_unlock_irq(&desc->lock);
175 }
176 mutex_unlock(&probing_active);
177
178 if (nr_of_irqs > 1)
179 irq_found = -irq_found;
180
181 return irq_found;
182 }
183 EXPORT_SYMBOL(probe_irq_off);
184