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 #include <asm/traps.h>
49
50 static unsigned long no_fiq_insn;
51
52 /* Default reacquire function
53 * - we always relinquish FIQ control
54 * - we always reacquire FIQ control
55 */
fiq_def_op(void * ref,int relinquish)56 static int fiq_def_op(void *ref, int relinquish)
57 {
58 if (!relinquish)
59 set_fiq_handler(&no_fiq_insn, sizeof(no_fiq_insn));
60
61 return 0;
62 }
63
64 static struct fiq_handler default_owner = {
65 .name = "default",
66 .fiq_op = fiq_def_op,
67 };
68
69 static struct fiq_handler *current_fiq = &default_owner;
70
show_fiq_list(struct seq_file * p,int prec)71 int show_fiq_list(struct seq_file *p, int prec)
72 {
73 if (current_fiq != &default_owner)
74 seq_printf(p, "%*s: %s\n", prec, "FIQ",
75 current_fiq->name);
76
77 return 0;
78 }
79
set_fiq_handler(void * start,unsigned int length)80 void set_fiq_handler(void *start, unsigned int length)
81 {
82 #if defined(CONFIG_CPU_USE_DOMAINS)
83 memcpy((void *)0xffff001c, start, length);
84 #else
85 memcpy(vectors_page + 0x1c, start, length);
86 #endif
87 flush_icache_range(0xffff001c, 0xffff001c + length);
88 if (!vectors_high())
89 flush_icache_range(0x1c, 0x1c + length);
90 }
91
92 /*
93 * Taking an interrupt in FIQ mode is death, so both these functions
94 * disable irqs for the duration. Note - these functions are almost
95 * entirely coded in assembly.
96 */
set_fiq_regs(struct pt_regs * regs)97 void __naked set_fiq_regs(struct pt_regs *regs)
98 {
99 register unsigned long tmp;
100 asm volatile (
101 "mov ip, sp\n\
102 stmfd sp!, {fp, ip, lr, pc}\n\
103 sub fp, ip, #4\n\
104 mrs %0, cpsr\n\
105 msr cpsr_c, %2 @ select FIQ mode\n\
106 mov r0, r0\n\
107 ldmia %1, {r8 - r14}\n\
108 msr cpsr_c, %0 @ return to SVC mode\n\
109 mov r0, r0\n\
110 ldmfd sp, {fp, sp, pc}"
111 : "=&r" (tmp)
112 : "r" (®s->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE));
113 }
114
get_fiq_regs(struct pt_regs * regs)115 void __naked get_fiq_regs(struct pt_regs *regs)
116 {
117 register unsigned long tmp;
118 asm volatile (
119 "mov ip, sp\n\
120 stmfd sp!, {fp, ip, lr, pc}\n\
121 sub fp, ip, #4\n\
122 mrs %0, cpsr\n\
123 msr cpsr_c, %2 @ select FIQ mode\n\
124 mov r0, r0\n\
125 stmia %1, {r8 - r14}\n\
126 msr cpsr_c, %0 @ return to SVC mode\n\
127 mov r0, r0\n\
128 ldmfd sp, {fp, sp, pc}"
129 : "=&r" (tmp)
130 : "r" (®s->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE));
131 }
132
claim_fiq(struct fiq_handler * f)133 int claim_fiq(struct fiq_handler *f)
134 {
135 int ret = 0;
136
137 if (current_fiq) {
138 ret = -EBUSY;
139
140 if (current_fiq->fiq_op != NULL)
141 ret = current_fiq->fiq_op(current_fiq->dev_id, 1);
142 }
143
144 if (!ret) {
145 f->next = current_fiq;
146 current_fiq = f;
147 }
148
149 return ret;
150 }
151
release_fiq(struct fiq_handler * f)152 void release_fiq(struct fiq_handler *f)
153 {
154 if (current_fiq != f) {
155 printk(KERN_ERR "%s FIQ trying to release %s FIQ\n",
156 f->name, current_fiq->name);
157 dump_stack();
158 return;
159 }
160
161 do
162 current_fiq = current_fiq->next;
163 while (current_fiq->fiq_op(current_fiq->dev_id, 0));
164 }
165
enable_fiq(int fiq)166 void enable_fiq(int fiq)
167 {
168 enable_irq(fiq + FIQ_START);
169 }
170
disable_fiq(int fiq)171 void disable_fiq(int fiq)
172 {
173 disable_irq(fiq + FIQ_START);
174 }
175
176 EXPORT_SYMBOL(set_fiq_handler);
177 EXPORT_SYMBOL(set_fiq_regs);
178 EXPORT_SYMBOL(get_fiq_regs);
179 EXPORT_SYMBOL(claim_fiq);
180 EXPORT_SYMBOL(release_fiq);
181 EXPORT_SYMBOL(enable_fiq);
182 EXPORT_SYMBOL(disable_fiq);
183
init_FIQ(void)184 void __init init_FIQ(void)
185 {
186 no_fiq_insn = *(unsigned long *)0xffff001c;
187 }
188