crunch.c

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/*
 * arch/arm/kernel/crunch.c
 * Cirrus MaverickCrunch context switching and handling
 *
 * Copyright (C) 2006 Lennert Buytenhek <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/signal.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/io.h>

#include <asm/thread_notify.h>

#include "soc.h"

struct crunch_state *crunch_owner;

void crunch_task_release(struct thread_info *thread)
{
    local_irq_disable();
    if (crunch_owner == &thread->crunchstate)
        crunch_owner = NULL;
    local_irq_enable();
}

static int crunch_enabled(u32 devcfg)
{
    return !!(devcfg & EP93XX_SYSCON_DEVCFG_CPENA);
}

static int crunch_do(struct notifier_block *self, unsigned long cmd, void *t)
{
    struct thread_info *thread = (struct thread_info *)t;
    struct crunch_state *crunch_state;
    u32 devcfg;

    crunch_state = &thread->crunchstate;

    switch (cmd) {
    case THREAD_NOTIFY_FLUSH:
        memset(crunch_state, 0, sizeof(*crunch_state));

        /*
         * FALLTHROUGH: Ensure we don't try to overwrite our newly
         * initialised state information on the first fault.
         */

    case THREAD_NOTIFY_EXIT:
        crunch_task_release(thread);
        break;

    case THREAD_NOTIFY_SWITCH:
        devcfg = __raw_readl(EP93XX_SYSCON_DEVCFG);
        if (crunch_enabled(devcfg) || crunch_owner == crunch_state) {
            /*
             * We don't use ep93xx_syscon_swlocked_write() here
             * because we are on the context switch path and
             * preemption is already disabled.
             */
            devcfg ^= EP93XX_SYSCON_DEVCFG_CPENA;
            __raw_writel(0xaa, EP93XX_SYSCON_SWLOCK);
            __raw_writel(devcfg, EP93XX_SYSCON_DEVCFG);
        }
        break;
    }

    return NOTIFY_DONE;
}

static struct notifier_block crunch_notifier_block = {
    .notifier_call  = crunch_do,
};

int __init crunch_init(void)
{
    thread_register_notifier(&crunch_notifier_block);
    elf_hwcap |= HWCAP_CRUNCH;

    return 0;
}