fiq.c

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/*
 *  linux/arch/arm/kernel/fiq.c
 *
 *  Copyright (C) 1998 Russell King
 *  Copyright (C) 1998, 1999 Phil Blundell
 *
 *  FIQ support written by Philip Blundell <[email protected]>, 1998.
 *
 *  FIQ support re-written by Russell King to be more generic
 *
 * We now properly support a method by which the FIQ handlers can
 * be stacked onto the vector.  We still do not support sharing
 * the FIQ vector itself.
 *
 * Operation is as follows:
 *  1. Owner A claims FIQ:
 *     - default_fiq relinquishes control.
 *  2. Owner A:
 *     - inserts code.
 *     - sets any registers,
 *     - enables FIQ.
 *  3. Owner B claims FIQ:
 *     - if owner A has a relinquish function.
 *       - disable FIQs.
 *       - saves any registers.
 *       - returns zero.
 *  4. Owner B:
 *     - inserts code.
 *     - sets any registers,
 *     - enables FIQ.
 *  5. Owner B releases FIQ:
 *     - Owner A is asked to reacquire FIQ:
 *   - inserts code.
 *   - restores saved registers.
 *   - enables FIQ.
 *  6. Goto 3
 */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/seq_file.h>

#include <asm/cacheflush.h>
#include <asm/cp15.h>
#include <asm/fiq.h>
#include <asm/irq.h>
#include <asm/traps.h>

static unsigned long no_fiq_insn;

/* Default reacquire function
 * - we always relinquish FIQ control
 * - we always reacquire FIQ control
 */
static int fiq_def_op(void *ref, int relinquish)
{
    if (!relinquish)
        set_fiq_handler(&no_fiq_insn, sizeof(no_fiq_insn));

    return 0;
}

static struct fiq_handler default_owner = {
    .name   = "default",
    .fiq_op = fiq_def_op,
};

static struct fiq_handler *current_fiq = &default_owner;

int show_fiq_list(struct seq_file *p, int prec)
{
    if (current_fiq != &default_owner)
        seq_printf(p, "%*s:              %s\n", prec, "FIQ",
            current_fiq->name);

    return 0;
}

void set_fiq_handler(void *start, unsigned int length)
{
#if defined(CONFIG_CPU_USE_DOMAINS)
    memcpy((void *)0xffff001c, start, length);
#else
    memcpy(vectors_page + 0x1c, start, length);
#endif
    flush_icache_range(0xffff001c, 0xffff001c + length);
    if (!vectors_high())
        flush_icache_range(0x1c, 0x1c + length);
}

int claim_fiq(struct fiq_handler *f)
{
    int ret = 0;

    if (current_fiq) {
        ret = -EBUSY;

        if (current_fiq->fiq_op != NULL)
            ret = current_fiq->fiq_op(current_fiq->dev_id, 1);
    }

    if (!ret) {
        f->next = current_fiq;
        current_fiq = f;
    }

    return ret;
}

void release_fiq(struct fiq_handler *f)
{
    if (current_fiq != f) {
        printk(KERN_ERR "%s FIQ trying to release %s FIQ\n",
               f->name, current_fiq->name);
        dump_stack();
        return;
    }

    do
        current_fiq = current_fiq->next;
    while (current_fiq->fiq_op(current_fiq->dev_id, 0));
}

static int fiq_start;

void enable_fiq(int fiq)
{
    enable_irq(fiq + fiq_start);
}

void disable_fiq(int fiq)
{
    disable_irq(fiq + fiq_start);
}

EXPORT_SYMBOL(set_fiq_handler);
EXPORT_SYMBOL(__set_fiq_regs);  /* defined in fiqasm.S */
EXPORT_SYMBOL(__get_fiq_regs);  /* defined in fiqasm.S */
EXPORT_SYMBOL(claim_fiq);
EXPORT_SYMBOL(release_fiq);
EXPORT_SYMBOL(enable_fiq);
EXPORT_SYMBOL(disable_fiq);

void __init init_FIQ(int start)
{
    no_fiq_insn = *(unsigned long *)0xffff001c;
    fiq_start = start;
}