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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/irq.h>
49 #include <asm/traps.h>
50 
51 #ifdef CONFIG_RANDOMIZE_BASE
52 #define FIQ_OFFSET ({					\
53 		extern void *vector_fiq_offset;		\
54 		(unsigned)&vector_fiq_offset - kaslr_offset(); \
55 	})
56 #else
57 #define FIQ_OFFSET ({					\
58 		extern void *vector_fiq_offset;		\
59 		(unsigned)&vector_fiq_offset;		\
60 	})
61 #endif
62 
63 static unsigned long dfl_fiq_insn;
64 static struct pt_regs dfl_fiq_regs;
65 
66 /* Default reacquire function
67  * - we always relinquish FIQ control
68  * - we always reacquire FIQ control
69  */
fiq_def_op(void * ref,int relinquish)70 static int fiq_def_op(void *ref, int relinquish)
71 {
72 	if (!relinquish) {
73 		/* Restore default handler and registers */
74 		local_fiq_disable();
75 		set_fiq_regs(&dfl_fiq_regs);
76 		set_fiq_handler(&dfl_fiq_insn, sizeof(dfl_fiq_insn));
77 		local_fiq_enable();
78 
79 		/* FIXME: notify irq controller to standard enable FIQs */
80 	}
81 
82 	return 0;
83 }
84 
85 static struct fiq_handler default_owner = {
86 	.name	= "default",
87 	.fiq_op = fiq_def_op,
88 };
89 
90 static struct fiq_handler *current_fiq = &default_owner;
91 
show_fiq_list(struct seq_file * p,int prec)92 int show_fiq_list(struct seq_file *p, int prec)
93 {
94 	if (current_fiq != &default_owner)
95 		seq_printf(p, "%*s:              %s\n", prec, "FIQ",
96 			current_fiq->name);
97 
98 	return 0;
99 }
100 
set_fiq_handler(void * start,unsigned int length)101 void set_fiq_handler(void *start, unsigned int length)
102 {
103 	void *base = vectors_page;
104 	unsigned offset = FIQ_OFFSET;
105 
106 	memcpy(base + offset, start, length);
107 	if (!cache_is_vipt_nonaliasing())
108 		flush_icache_range((unsigned long)base + offset,
109 				   (unsigned long)base + offset + length);
110 	flush_icache_range(0xffff0000 + offset, 0xffff0000 + offset + length);
111 }
112 
claim_fiq(struct fiq_handler * f)113 int claim_fiq(struct fiq_handler *f)
114 {
115 	int ret = 0;
116 
117 	if (current_fiq) {
118 		ret = -EBUSY;
119 
120 		if (current_fiq->fiq_op != NULL)
121 			ret = current_fiq->fiq_op(current_fiq->dev_id, 1);
122 	}
123 
124 	if (!ret) {
125 		f->next = current_fiq;
126 		current_fiq = f;
127 	}
128 
129 	return ret;
130 }
131 
release_fiq(struct fiq_handler * f)132 void release_fiq(struct fiq_handler *f)
133 {
134 	if (current_fiq != f) {
135 		pr_err("%s FIQ trying to release %s FIQ\n",
136 		       f->name, current_fiq->name);
137 		dump_stack();
138 		return;
139 	}
140 
141 	do
142 		current_fiq = current_fiq->next;
143 	while (current_fiq->fiq_op(current_fiq->dev_id, 0));
144 }
145 
146 static int fiq_start;
147 
enable_fiq(int fiq)148 void enable_fiq(int fiq)
149 {
150 	enable_irq(fiq + fiq_start);
151 }
152 
disable_fiq(int fiq)153 void disable_fiq(int fiq)
154 {
155 	disable_irq(fiq + fiq_start);
156 }
157 
158 EXPORT_SYMBOL(set_fiq_handler);
159 EXPORT_SYMBOL(__set_fiq_regs);	/* defined in fiqasm.S */
160 EXPORT_SYMBOL(__get_fiq_regs);	/* defined in fiqasm.S */
161 EXPORT_SYMBOL(claim_fiq);
162 EXPORT_SYMBOL(release_fiq);
163 EXPORT_SYMBOL(enable_fiq);
164 EXPORT_SYMBOL(disable_fiq);
165 
init_FIQ(int start)166 void __init init_FIQ(int start)
167 {
168 	unsigned offset = FIQ_OFFSET;
169 	dfl_fiq_insn = *(unsigned long *)(0xffff0000 + offset);
170 	get_fiq_regs(&dfl_fiq_regs);
171 	fiq_start = start;
172 }
173