1/*
2 *  linux/arch/arm26/kernel/fiq.c
3 *
4 *  Copyright (C) 1998 Russell King
5 *  Copyright (C) 1998, 1999 Phil Blundell
6 *  Copyright (C) 2003 Ian Molton
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/mm.h>
41#include <linux/mman.h>
42#include <linux/init.h>
43#include <linux/seq_file.h>
44
45#include <asm/fiq.h>
46#include <asm/io.h>
47#include <asm/irq.h>
48#include <asm/pgalloc.h>
49#include <asm/system.h>
50#include <asm/uaccess.h>
51
52#define FIQ_VECTOR (vectors_base() + 0x1c)
53
54static unsigned long no_fiq_insn;
55
56#define unprotect_page_0()
57#define protect_page_0()
58
59/* Default reacquire function
60 * - we always relinquish FIQ control
61 * - we always reacquire FIQ control
62 */
63static int fiq_def_op(void *ref, int relinquish)
64{
65	if (!relinquish) {
66		unprotect_page_0();
67		*(unsigned long *)FIQ_VECTOR = no_fiq_insn;
68		protect_page_0();
69	}
70
71	return 0;
72}
73
74static struct fiq_handler default_owner = {
75	.name	= "default",
76	.fiq_op = fiq_def_op,
77};
78
79static struct fiq_handler *current_fiq = &default_owner;
80
81int show_fiq_list(struct seq_file *p, void *v)
82{
83	if (current_fiq != &default_owner)
84		seq_printf(p, "FIQ:              %s\n", current_fiq->name);
85
86	return 0;
87}
88
89void set_fiq_handler(void *start, unsigned int length)
90{
91	unprotect_page_0();
92
93	memcpy((void *)FIQ_VECTOR, start, length);
94
95	protect_page_0();
96}
97
98/*
99 * Taking an interrupt in FIQ mode is death, so both these functions
100 * disable irqs for the duration.
101 */
102void set_fiq_regs(struct pt_regs *regs)
103{
104	register unsigned long tmp, tmp2;
105	__asm__ volatile (
106	"mov	%0, pc					\n"
107	"bic	%1, %0, #0x3				\n"
108	"orr	%1, %1, %3				\n"
109	"teqp	%1, #0		@ select FIQ mode	\n"
110	"mov	r0, r0					\n"
111	"ldmia	%2, {r8 - r14}				\n"
112	"teqp	%0, #0		@ return to SVC mode	\n"
113	"mov	r0, r0					"
114	: "=&r" (tmp), "=&r" (tmp2)
115	: "r" (&regs->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | MODE_FIQ26)
116	/* These registers aren't modified by the above code in a way
117	   visible to the compiler, but we mark them as clobbers anyway
118	   so that GCC won't put any of the input or output operands in
119	   them.  */
120	: "r8", "r9", "r10", "r11", "r12", "r13", "r14");
121}
122
123void get_fiq_regs(struct pt_regs *regs)
124{
125	register unsigned long tmp, tmp2;
126	__asm__ volatile (
127	"mov	%0, pc					\n"
128	"bic	%1, %0, #0x3				\n"
129	"orr	%1, %1, %3				\n"
130	"teqp	%1, #0		@ select FIQ mode	\n"
131	"mov	r0, r0					\n"
132	"stmia	%2, {r8 - r14}				\n"
133	"teqp	%0, #0		@ return to SVC mode	\n"
134	"mov	r0, r0					"
135	: "=&r" (tmp), "=&r" (tmp2)
136	: "r" (&regs->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | MODE_FIQ26)
137	/* These registers aren't modified by the above code in a way
138	   visible to the compiler, but we mark them as clobbers anyway
139	   so that GCC won't put any of the input or output operands in
140	   them.  */
141	: "r8", "r9", "r10", "r11", "r12", "r13", "r14");
142}
143
144int claim_fiq(struct fiq_handler *f)
145{
146	int ret = 0;
147
148	if (current_fiq) {
149		ret = -EBUSY;
150
151		if (current_fiq->fiq_op != NULL)
152			ret = current_fiq->fiq_op(current_fiq->dev_id, 1);
153	}
154
155	if (!ret) {
156		f->next = current_fiq;
157		current_fiq = f;
158	}
159
160	return ret;
161}
162
163void release_fiq(struct fiq_handler *f)
164{
165	if (current_fiq != f) {
166		printk(KERN_ERR "%s FIQ trying to release %s FIQ\n",
167		       f->name, current_fiq->name);
168#ifdef CONFIG_DEBUG_ERRORS
169		__backtrace();
170#endif
171		return;
172	}
173
174	do
175		current_fiq = current_fiq->next;
176	while (current_fiq->fiq_op(current_fiq->dev_id, 0));
177}
178
179void enable_fiq(int fiq)
180{
181	enable_irq(fiq + FIQ_START);
182}
183
184void disable_fiq(int fiq)
185{
186	disable_irq(fiq + FIQ_START);
187}
188
189EXPORT_SYMBOL(set_fiq_handler);
190EXPORT_SYMBOL(set_fiq_regs);
191EXPORT_SYMBOL(get_fiq_regs);
192EXPORT_SYMBOL(claim_fiq);
193EXPORT_SYMBOL(release_fiq);
194EXPORT_SYMBOL(enable_fiq);
195EXPORT_SYMBOL(disable_fiq);
196
197void __init init_FIQ(void)
198{
199	no_fiq_insn = *(unsigned long *)FIQ_VECTOR;
200	set_fs(get_fs());
201}
202