1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * linux/arch/alpha/kernel/irq_i8259.c
4 *
5 * This is the 'legacy' 8259A Programmable Interrupt Controller,
6 * present in the majority of PC/AT boxes.
7 *
8 * Started hacking from linux-2.3.30pre6/arch/i386/kernel/i8259.c.
9 */
10
11 #include <linux/init.h>
12 #include <linux/cache.h>
13 #include <linux/sched.h>
14 #include <linux/irq.h>
15 #include <linux/interrupt.h>
16
17 #include <asm/io.h>
18
19 #include "proto.h"
20 #include "irq_impl.h"
21
22
23 /* Note mask bit is true for DISABLED irqs. */
24 static unsigned int cached_irq_mask = 0xffff;
25 static DEFINE_SPINLOCK(i8259_irq_lock);
26
27 static inline void
28 i8259_update_irq_hw(unsigned int irq, unsigned long mask)
29 {
30 int port = 0x21;
31 if (irq & 8) mask >>= 8;
32 if (irq & 8) port = 0xA1;
33 outb(mask, port);
34 }
35
36 inline void
37 i8259a_enable_irq(struct irq_data *d)
38 {
39 spin_lock(&i8259_irq_lock);
40 i8259_update_irq_hw(d->irq, cached_irq_mask &= ~(1 << d->irq));
41 spin_unlock(&i8259_irq_lock);
42 }
43
44 static inline void
45 __i8259a_disable_irq(unsigned int irq)
46 {
47 i8259_update_irq_hw(irq, cached_irq_mask |= 1 << irq);
48 }
49
50 void
51 i8259a_disable_irq(struct irq_data *d)
52 {
53 spin_lock(&i8259_irq_lock);
54 __i8259a_disable_irq(d->irq);
55 spin_unlock(&i8259_irq_lock);
56 }
57
58 void
59 i8259a_mask_and_ack_irq(struct irq_data *d)
60 {
61 unsigned int irq = d->irq;
62
63 spin_lock(&i8259_irq_lock);
64 __i8259a_disable_irq(irq);
65
66 /* Ack the interrupt making it the lowest priority. */
67 if (irq >= 8) {
68 outb(0xE0 | (irq - 8), 0xa0); /* ack the slave */
69 irq = 2;
70 }
71 outb(0xE0 | irq, 0x20); /* ack the master */
72 spin_unlock(&i8259_irq_lock);
73 }
74
75 struct irq_chip i8259a_irq_type = {
76 .name = "XT-PIC",
77 .irq_unmask = i8259a_enable_irq,
78 .irq_mask = i8259a_disable_irq,
79 .irq_mask_ack = i8259a_mask_and_ack_irq,
80 };
81
82 void __init
83 init_i8259a_irqs(void)
84 {
85 long i;
86
87 outb(0xff, 0x21); /* mask all of 8259A-1 */
88 outb(0xff, 0xA1); /* mask all of 8259A-2 */
89
90 for (i = 0; i < 16; i++) {
91 irq_set_chip_and_handler(i, &i8259a_irq_type, handle_level_irq);
92 }
93
94 if (request_irq(2, no_action, 0, "cascade", NULL))
95 pr_err("Failed to request irq 2 (cascade)\n");
96 }
97
98
99 #if defined(CONFIG_ALPHA_GENERIC)
100 # define IACK_SC alpha_mv.iack_sc
101 #elif defined(CONFIG_ALPHA_CIA)
102 # define IACK_SC CIA_IACK_SC
103 #elif defined(CONFIG_ALPHA_PYXIS)
104 # define IACK_SC PYXIS_IACK_SC
105 #elif defined(CONFIG_ALPHA_TITAN)
106 # define IACK_SC TITAN_IACK_SC
107 #elif defined(CONFIG_ALPHA_TSUNAMI)
108 # define IACK_SC TSUNAMI_IACK_SC
109 #elif defined(CONFIG_ALPHA_IRONGATE)
110 # define IACK_SC IRONGATE_IACK_SC
111 #endif
112 /* Note that CONFIG_ALPHA_POLARIS is intentionally left out here, since
113 sys_rx164 wants to use isa_no_iack_sc_device_interrupt for some reason. */
114
115 #if defined(IACK_SC)
116 void
117 isa_device_interrupt(unsigned long vector)
118 {
119 /*
120 * Generate a PCI interrupt acknowledge cycle. The PIC will
121 * respond with the interrupt vector of the highest priority
122 * interrupt that is pending. The PALcode sets up the
123 * interrupts vectors such that irq level L generates vector L.
124 */
125 int j = *(vuip) IACK_SC;
126 j &= 0xff;
127 handle_irq(j);
128 }
129 #endif
130
131 #if defined(CONFIG_ALPHA_GENERIC) || !defined(IACK_SC)
132 void
133 isa_no_iack_sc_device_interrupt(unsigned long vector)
134 {
135 unsigned long pic;
136
137 /*
138 * It seems to me that the probability of two or more *device*
139 * interrupts occurring at almost exactly the same time is
140 * pretty low. So why pay the price of checking for
141 * additional interrupts here if the common case can be
142 * handled so much easier?
143 */
144 /*
145 * The first read of gives you *all* interrupting lines.
146 * Therefore, read the mask register and and out those lines
147 * not enabled. Note that some documentation has 21 and a1
148 * write only. This is not true.
149 */
150 pic = inb(0x20) | (inb(0xA0) << 8); /* read isr */
151 pic &= 0xFFFB; /* mask out cascade & hibits */
152
153 while (pic) {
154 int j = ffz(~pic);
155 pic &= pic - 1;
156 handle_irq(j);
157 }
158 }
159 #endif
160
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