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/irq.h>
49 #include <asm/traps.h>
50
51 #define FIQ_OFFSET ({ \
52 extern void *vector_fiq_offset; \
53 (unsigned)&vector_fiq_offset; \
54 })
55
56 static unsigned long dfl_fiq_insn;
57 static struct pt_regs dfl_fiq_regs;
58
59 /* Default reacquire function
60 * - we always relinquish FIQ control
61 * - we always reacquire FIQ control
62 */
fiq_def_op(void * ref,int relinquish)63 static int fiq_def_op(void *ref, int relinquish)
64 {
65 if (!relinquish) {
66 /* Restore default handler and registers */
67 local_fiq_disable();
68 set_fiq_regs(&dfl_fiq_regs);
69 set_fiq_handler(&dfl_fiq_insn, sizeof(dfl_fiq_insn));
70 local_fiq_enable();
71
72 /* FIXME: notify irq controller to standard enable FIQs */
73 }
74
75 return 0;
76 }
77
78 static struct fiq_handler default_owner = {
79 .name = "default",
80 .fiq_op = fiq_def_op,
81 };
82
83 static struct fiq_handler *current_fiq = &default_owner;
84
show_fiq_list(struct seq_file * p,int prec)85 int show_fiq_list(struct seq_file *p, int prec)
86 {
87 if (current_fiq != &default_owner)
88 seq_printf(p, "%*s: %s\n", prec, "FIQ",
89 current_fiq->name);
90
91 return 0;
92 }
93
set_fiq_handler(void * start,unsigned int length)94 void set_fiq_handler(void *start, unsigned int length)
95 {
96 void *base = vectors_page;
97 unsigned offset = FIQ_OFFSET;
98
99 memcpy(base + offset, start, length);
100 if (!cache_is_vipt_nonaliasing())
101 flush_icache_range((unsigned long)base + offset,
102 (unsigned long)base + offset + length);
103 flush_icache_range(0xffff0000 + offset, 0xffff0000 + offset + length);
104 }
105
claim_fiq(struct fiq_handler * f)106 int claim_fiq(struct fiq_handler *f)
107 {
108 int ret = 0;
109
110 if (current_fiq) {
111 ret = -EBUSY;
112
113 if (current_fiq->fiq_op != NULL)
114 ret = current_fiq->fiq_op(current_fiq->dev_id, 1);
115 }
116
117 if (!ret) {
118 f->next = current_fiq;
119 current_fiq = f;
120 }
121
122 return ret;
123 }
124
release_fiq(struct fiq_handler * f)125 void release_fiq(struct fiq_handler *f)
126 {
127 if (current_fiq != f) {
128 pr_err("%s FIQ trying to release %s FIQ\n",
129 f->name, current_fiq->name);
130 dump_stack();
131 return;
132 }
133
134 do
135 current_fiq = current_fiq->next;
136 while (current_fiq->fiq_op(current_fiq->dev_id, 0));
137 }
138
139 static int fiq_start;
140
enable_fiq(int fiq)141 void enable_fiq(int fiq)
142 {
143 enable_irq(fiq + fiq_start);
144 }
145
disable_fiq(int fiq)146 void disable_fiq(int fiq)
147 {
148 disable_irq(fiq + fiq_start);
149 }
150
151 EXPORT_SYMBOL(set_fiq_handler);
152 EXPORT_SYMBOL(__set_fiq_regs); /* defined in fiqasm.S */
153 EXPORT_SYMBOL(__get_fiq_regs); /* defined in fiqasm.S */
154 EXPORT_SYMBOL(claim_fiq);
155 EXPORT_SYMBOL(release_fiq);
156 EXPORT_SYMBOL(enable_fiq);
157 EXPORT_SYMBOL(disable_fiq);
158
init_FIQ(int start)159 void __init init_FIQ(int start)
160 {
161 unsigned offset = FIQ_OFFSET;
162 dfl_fiq_insn = *(unsigned long *)(0xffff0000 + offset);
163 get_fiq_regs(&dfl_fiq_regs);
164 fiq_start = start;
165 }
166