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crunch.c

/*
 * arch/arm/kernel/crunch.c
 * Cirrus MaverickCrunch context switching and handling
 *
 * Copyright (C) 2006 Lennert Buytenhek <buytenh@wantstofly.org>
 *
 * 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 <mach/ep93xx-regs.h>
#include <asm/thread_notify.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_DEVICE_CONFIG_CRUNCH_ENABLE);
}

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_RELEASE:
            crunch_task_release(thread);
            break;

      case THREAD_NOTIFY_SWITCH:
            devcfg = __raw_readl(EP93XX_SYSCON_DEVICE_CONFIG);
            if (crunch_enabled(devcfg) || crunch_owner == crunch_state) {
                  devcfg ^= EP93XX_SYSCON_DEVICE_CONFIG_CRUNCH_ENABLE;
                  __raw_writel(0xaa, EP93XX_SYSCON_SWLOCK);
                  __raw_writel(devcfg, EP93XX_SYSCON_DEVICE_CONFIG);
            }
            break;
      }

      return NOTIFY_DONE;
}

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

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

      return 0;
}

late_initcall(crunch_init);

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