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pj4-cp0.c

/*
 * linux/arch/arm/kernel/pj4-cp0.c
 *
 * PJ4 iWMMXt coprocessor context switching and handling
 *
 * Copyright (c) 2010 Marvell International Inc.
 *
 * 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>

static int iwmmxt_do(struct notifier_block *self, unsigned long cmd, void *t)
{
      struct thread_info *thread = t;

      switch (cmd) {
      case THREAD_NOTIFY_FLUSH:
            /*
             * flush_thread() zeroes thread->fpstate, so no need
             * to do anything here.
             *
             * FALLTHROUGH: Ensure we don't try to overwrite our newly
             * initialised state information on the first fault.
             */

      case THREAD_NOTIFY_EXIT:
            iwmmxt_task_release(thread);
            break;

      case THREAD_NOTIFY_SWITCH:
            iwmmxt_task_switch(thread);
            break;
      }

      return NOTIFY_DONE;
}

static struct notifier_block iwmmxt_notifier_block = {
      .notifier_call    = iwmmxt_do,
};


static u32 __init pj4_cp_access_read(void)
{
      u32 value;

      __asm__ __volatile__ (
            "mrc  p15, 0, %0, c1, c0, 2\n\t"
            : "=r" (value));
      return value;
}

static void __init pj4_cp_access_write(u32 value)
{
      u32 temp;

      __asm__ __volatile__ (
            "mcr  p15, 0, %1, c1, c0, 2\n\t"
            "mrc  p15, 0, %0, c1, c0, 2\n\t"
            "mov  %0, %0\n\t"
            "sub  pc, pc, #4\n\t"
            : "=r" (temp) : "r" (value));
}


/*
 * Disable CP0/CP1 on boot, and let call_fpe() and the iWMMXt lazy
 * switch code handle iWMMXt context switching.
 */
static int __init pj4_cp0_init(void)
{
      u32 cp_access;

      cp_access = pj4_cp_access_read() & ~0xf;
      pj4_cp_access_write(cp_access);

      printk(KERN_INFO "PJ4 iWMMXt coprocessor enabled.\n");
      elf_hwcap |= HWCAP_IWMMXT;
      thread_register_notifier(&iwmmxt_notifier_block);

      return 0;
}

late_initcall(pj4_cp0_init);

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