1 /*
2 * linux/arch/arm/kernel/fiq.c
3 *
4 * Copyright (C) 1998 Russell King
5 * Copyright (C) 1998, 1999 Phil Blundell
6 *
7 * FIQ support written by Philip Blundell <philb@gnu.org>, 1998.
8 *
9 * FIQ support re-written by Russell King to be more generic
10 *
11 * We now properly support a method by which the FIQ handlers can
12 * be stacked onto the vector. We still do not support sharing
13 * the FIQ vector itself.
14 *
15 * Operation is as follows:
16 * 1. Owner A claims FIQ:
17 * - default_fiq relinquishes control.
18 * 2. Owner A:
19 * - inserts code.
20 * - sets any registers,
21 * - enables FIQ.
22 * 3. Owner B claims FIQ:
23 * - if owner A has a relinquish function.
24 * - disable FIQs.
25 * - saves any registers.
26 * - returns zero.
27 * 4. Owner B:
28 * - inserts code.
29 * - sets any registers,
30 * - enables FIQ.
31 * 5. Owner B releases FIQ:
32 * - Owner A is asked to reacquire FIQ:
33 * - inserts code.
34 * - restores saved registers.
35 * - enables FIQ.
36 * 6. Goto 3
37 */
38 #include <linux/module.h>
39 #include <linux/kernel.h>
40 #include <linux/init.h>
41 #include <linux/interrupt.h>
42 #include <linux/seq_file.h>
43
44 #include <asm/cacheflush.h>
45 #include <asm/fiq.h>
46 #include <asm/irq.h>
47 #include <asm/system.h>
48
49 static unsigned long no_fiq_insn;
50
51 /* Default reacquire function
52 * - we always relinquish FIQ control
53 * - we always reacquire FIQ control
54 */
55 static int fiq_def_op(void *ref, int relinquish)
56 {
57 if (!relinquish)
58 set_fiq_handler(&no_fiq_insn, sizeof(no_fiq_insn));
59
60 return 0;
61 }
62
63 static struct fiq_handler default_owner = {
64 .name = "default",
65 .fiq_op = fiq_def_op,
66 };
67
68 static struct fiq_handler *current_fiq = &default_owner;
69
70 int show_fiq_list(struct seq_file *p, void *v)
71 {
72 if (current_fiq != &default_owner)
73 seq_printf(p, "FIQ: %s\n", current_fiq->name);
74
75 return 0;
76 }
77
78 void set_fiq_handler(void *start, unsigned int length)
79 {
80 memcpy((void *)0xffff001c, start, length);
81 flush_icache_range(0xffff001c, 0xffff001c + length);
82 if (!vectors_high())
83 flush_icache_range(0x1c, 0x1c + length);
84 }
85
86 /*
87 * Taking an interrupt in FIQ mode is death, so both these functions
88 * disable irqs for the duration. Note - these functions are almost
89 * entirely coded in assembly.
90 */
91 void __naked set_fiq_regs(struct pt_regs *regs)
92 {
93 register unsigned long tmp;
94 asm volatile (
95 "mov ip, sp\n\
96 stmfd sp!, {fp, ip, lr, pc}\n\
97 sub fp, ip, #4\n\
98 mrs %0, cpsr\n\
99 msr cpsr_c, %2 @ select FIQ mode\n\
100 mov r0, r0\n\
101 ldmia %1, {r8 - r14}\n\
102 msr cpsr_c, %0 @ return to SVC mode\n\
103 mov r0, r0\n\
104 ldmfd sp, {fp, sp, pc}"
105 : "=&r" (tmp)
106 : "r" (®s->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE));
107 }
108
109 void __naked get_fiq_regs(struct pt_regs *regs)
110 {
111 register unsigned long tmp;
112 asm volatile (
113 "mov ip, sp\n\
114 stmfd sp!, {fp, ip, lr, pc}\n\
115 sub fp, ip, #4\n\
116 mrs %0, cpsr\n\
117 msr cpsr_c, %2 @ select FIQ mode\n\
118 mov r0, r0\n\
119 stmia %1, {r8 - r14}\n\
120 msr cpsr_c, %0 @ return to SVC mode\n\
121 mov r0, r0\n\
122 ldmfd sp, {fp, sp, pc}"
123 : "=&r" (tmp)
124 : "r" (®s->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE));
125 }
126
127 int claim_fiq(struct fiq_handler *f)
128 {
129 int ret = 0;
130
131 if (current_fiq) {
132 ret = -EBUSY;
133
134 if (current_fiq->fiq_op != NULL)
135 ret = current_fiq->fiq_op(current_fiq->dev_id, 1);
136 }
137
138 if (!ret) {
139 f->next = current_fiq;
140 current_fiq = f;
141 }
142
143 return ret;
144 }
145
146 void release_fiq(struct fiq_handler *f)
147 {
148 if (current_fiq != f) {
149 printk(KERN_ERR "%s FIQ trying to release %s FIQ\n",
150 f->name, current_fiq->name);
151 dump_stack();
152 return;
153 }
154
155 do
156 current_fiq = current_fiq->next;
157 while (current_fiq->fiq_op(current_fiq->dev_id, 0));
158 }
159
160 void enable_fiq(int fiq)
161 {
162 enable_irq(fiq + FIQ_START);
163 }
164
165 void disable_fiq(int fiq)
166 {
167 disable_irq(fiq + FIQ_START);
168 }
169
170 EXPORT_SYMBOL(set_fiq_handler);
171 EXPORT_SYMBOL(set_fiq_regs);
172 EXPORT_SYMBOL(get_fiq_regs);
173 EXPORT_SYMBOL(claim_fiq);
174 EXPORT_SYMBOL(release_fiq);
175 EXPORT_SYMBOL(enable_fiq);
176 EXPORT_SYMBOL(disable_fiq);
177
178 void __init init_FIQ(void)
179 {
180 no_fiq_insn = *(unsigned long *)0xffff001c;
181 }
182
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