xref: /linux/arch/arm/kernel/fiq.c (revision cdd5b5a9761fd66d17586e4f4ba6588c70e640ea)
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 
57 static unsigned long dfl_fiq_insn;
58 static struct pt_regs dfl_fiq_regs;
59 
60 /* Default reacquire function
61  * - we always relinquish FIQ control
62  * - we always reacquire FIQ control
63  */
fiq_def_op(void * ref,int relinquish)64 static 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 
79 static struct fiq_handler default_owner = {
80 	.name	= "default",
81 	.fiq_op = fiq_def_op,
82 };
83 
84 static struct fiq_handler *current_fiq = &default_owner;
85 
show_fiq_list(struct seq_file * p,int prec)86 int show_fiq_list(struct seq_file *p, int prec)
87 {
88 	if (current_fiq != &default_owner)
89 		seq_printf(p, "%*s:              %s\n", prec, "FIQ",
90 			current_fiq->name);
91 
92 	return 0;
93 }
94 
set_fiq_handler(void * start,unsigned int length)95 void 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((unsigned long)base + offset,
103 				   (unsigned long)base + offset + length);
104 	flush_icache_range(0xffff0000 + offset, 0xffff0000 + offset + length);
105 }
106 
claim_fiq(struct fiq_handler * f)107 int 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 
release_fiq(struct fiq_handler * f)126 void 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 
140 static int fiq_start;
141 
enable_fiq(int fiq)142 void enable_fiq(int fiq)
143 {
144 	enable_irq(fiq + fiq_start);
145 }
146 
disable_fiq(int fiq)147 void disable_fiq(int fiq)
148 {
149 	disable_irq(fiq + fiq_start);
150 }
151 
152 EXPORT_SYMBOL(set_fiq_handler);
153 EXPORT_SYMBOL(__set_fiq_regs);	/* defined in fiqasm.S */
154 EXPORT_SYMBOL(__get_fiq_regs);	/* defined in fiqasm.S */
155 EXPORT_SYMBOL(claim_fiq);
156 EXPORT_SYMBOL(release_fiq);
157 EXPORT_SYMBOL(enable_fiq);
158 EXPORT_SYMBOL(disable_fiq);
159 
init_FIQ(int start)160 void __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