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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/arch/arm/kernel/fiq.c
4 *
5 * Copyright (C) 1998 Russell King
6 * Copyright (C) 1998, 1999 Phil Blundell
7 *
8 * FIQ support written by Philip Blundell <philb@gnu.org>, 1998.
9 *
10 * FIQ support re-written by Russell King to be more generic
11 *
12 * We now properly support a method by which the FIQ handlers can
13 * be stacked onto the vector. We still do not support sharing
14 * the FIQ vector itself.
15 *
16 * Operation is as follows:
17 * 1. Owner A claims FIQ:
18 * - default_fiq relinquishes control.
19 * 2. Owner A:
20 * - inserts code.
21 * - sets any registers,
22 * - enables FIQ.
23 * 3. Owner B claims FIQ:
24 * - if owner A has a relinquish function.
25 * - disable FIQs.
26 * - saves any registers.
27 * - returns zero.
28 * 4. Owner B:
29 * - inserts code.
30 * - sets any registers,
31 * - enables FIQ.
32 * 5. Owner B releases FIQ:
33 * - Owner A is asked to reacquire FIQ:
34 * - inserts code.
35 * - restores saved registers.
36 * - enables FIQ.
37 * 6. Goto 3
38 */
39#include <linux/module.h>
40#include <linux/kernel.h>
41#include <linux/init.h>
42#include <linux/interrupt.h>
43#include <linux/seq_file.h>
44
45#include <asm/cacheflush.h>
46#include <asm/cp15.h>
47#include <asm/fiq.h>
48#include <asm/mach/irq.h>
49#include <asm/irq.h>
50#include <asm/traps.h>
51
52#define FIQ_OFFSET ({ \
53 extern void *vector_fiq_offset; \
54 (unsigned)&vector_fiq_offset; \
55 })
56
57static unsigned long dfl_fiq_insn;
58static struct pt_regs dfl_fiq_regs;
59
60/* Default reacquire function
61 * - we always relinquish FIQ control
62 * - we always reacquire FIQ control
63 */
64static int fiq_def_op(void *ref, int relinquish)
65{
66 if (!relinquish) {
67 /* Restore default handler and registers */
68 local_fiq_disable();
69 set_fiq_regs(&dfl_fiq_regs);
70 set_fiq_handler(&dfl_fiq_insn, sizeof(dfl_fiq_insn));
71 local_fiq_enable();
72
73 /* FIXME: notify irq controller to standard enable FIQs */
74 }
75
76 return 0;
77}
78
79static struct fiq_handler default_owner = {
80 .name = "default",
81 .fiq_op = fiq_def_op,
82};
83
84static struct fiq_handler *current_fiq = &default_owner;
85
86int show_fiq_list(struct seq_file *p, int prec)
87{
88 if (current_fiq != &default_owner)
89 seq_printf(m: p, fmt: "%*s: %s\n", prec, "FIQ",
90 current_fiq->name);
91
92 return 0;
93}
94
95void set_fiq_handler(void *start, unsigned int length)
96{
97 void *base = vectors_page;
98 unsigned offset = FIQ_OFFSET;
99
100 memcpy(base + offset, start, length);
101 if (!cache_is_vipt_nonaliasing())
102 flush_icache_range(start: (unsigned long)base + offset,
103 end: (unsigned long)base + offset + length);
104 flush_icache_range(start: 0xffff0000 + offset, end: 0xffff0000 + offset + length);
105}
106
107int claim_fiq(struct fiq_handler *f)
108{
109 int ret = 0;
110
111 if (current_fiq) {
112 ret = -EBUSY;
113
114 if (current_fiq->fiq_op != NULL)
115 ret = current_fiq->fiq_op(current_fiq->dev_id, 1);
116 }
117
118 if (!ret) {
119 f->next = current_fiq;
120 current_fiq = f;
121 }
122
123 return ret;
124}
125
126void release_fiq(struct fiq_handler *f)
127{
128 if (current_fiq != f) {
129 pr_err("%s FIQ trying to release %s FIQ\n",
130 f->name, current_fiq->name);
131 dump_stack();
132 return;
133 }
134
135 do
136 current_fiq = current_fiq->next;
137 while (current_fiq->fiq_op(current_fiq->dev_id, 0));
138}
139
140static int fiq_start;
141
142void enable_fiq(int fiq)
143{
144 enable_irq(irq: fiq + fiq_start);
145}
146
147void disable_fiq(int fiq)
148{
149 disable_irq(irq: fiq + fiq_start);
150}
151
152EXPORT_SYMBOL(set_fiq_handler);
153EXPORT_SYMBOL(__set_fiq_regs); /* defined in fiqasm.S */
154EXPORT_SYMBOL(__get_fiq_regs); /* defined in fiqasm.S */
155EXPORT_SYMBOL(claim_fiq);
156EXPORT_SYMBOL(release_fiq);
157EXPORT_SYMBOL(enable_fiq);
158EXPORT_SYMBOL(disable_fiq);
159
160void __init init_FIQ(int start)
161{
162 unsigned offset = FIQ_OFFSET;
163 dfl_fiq_insn = *(unsigned long *)(0xffff0000 + offset);
164 get_fiq_regs(&dfl_fiq_regs);
165 fiq_start = start;
166}
167

source code of linux/arch/arm/kernel/fiq.c