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/arch/arm/kernel/fiq.c

https://bitbucket.org/evzijst/gittest
C | 181 lines | 113 code | 22 blank | 46 comment | 11 complexity | 9a13cc73c969ef8f9607fb3c0bb96e30 MD5 | raw file
  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/seq_file.h>
 42
 43#include <asm/cacheflush.h>
 44#include <asm/fiq.h>
 45#include <asm/irq.h>
 46#include <asm/system.h>
 47#include <asm/uaccess.h>
 48
 49static unsigned long no_fiq_insn;
 50
 51/* Default reacquire function
 52 * - we always relinquish FIQ control
 53 * - we always reacquire FIQ control
 54 */
 55static 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
 63static struct fiq_handler default_owner = {
 64	.name	= "default",
 65	.fiq_op = fiq_def_op,
 66};
 67
 68static struct fiq_handler *current_fiq = &default_owner;
 69
 70int 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
 78void 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 */
 91void __attribute__((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	ldmea	fp, {fp, sp, pc}"
105	: "=&r" (tmp)
106	: "r" (&regs->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE));
107}
108
109void __attribute__((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	ldmea	fp, {fp, sp, pc}"
123	: "=&r" (tmp)
124	: "r" (&regs->ARM_r8), "I" (PSR_I_BIT | PSR_F_BIT | FIQ_MODE));
125}
126
127int 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
146void 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
160void enable_fiq(int fiq)
161{
162	enable_irq(fiq + FIQ_START);
163}
164
165void disable_fiq(int fiq)
166{
167	disable_irq(fiq + FIQ_START);
168}
169
170EXPORT_SYMBOL(set_fiq_handler);
171EXPORT_SYMBOL(set_fiq_regs);
172EXPORT_SYMBOL(get_fiq_regs);
173EXPORT_SYMBOL(claim_fiq);
174EXPORT_SYMBOL(release_fiq);
175EXPORT_SYMBOL(enable_fiq);
176EXPORT_SYMBOL(disable_fiq);
177
178void __init init_FIQ(void)
179{
180	no_fiq_insn = *(unsigned long *)0xffff001c;
181}