LXR linux/arch/microblaze/mm/mmu

   1/*
   2 * This file contains the routines for handling the MMU.
   3 *
   4 *    Copyright (C) 2007 Xilinx, Inc.  All rights reserved.
   5 *
   6 *  Derived from arch/ppc/mm/4xx_mmu.c:
   7 *  -- paulus
   8 *
   9 *  Derived from arch/ppc/mm/init.c:
  10 *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
  11 *
  12 *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
  13 *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
  14 *    Copyright (C) 1996 Paul Mackerras
  15 *  Amiga/APUS changes by Jesper Skov (jskov@cygnus.co.uk).
  16 *
  17 *  Derived from "arch/i386/mm/init.c"
  18 *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
  19 *
  20 *  This program is free software; you can redistribute it and/or
  21 *  modify it under the terms of the GNU General Public License
  22 *  as published by the Free Software Foundation; either version
  23 *  2 of the License, or (at your option) any later version.
  24 *
  25 */
  26
  27#include <linux/mm.h>
  28#include <linux/init.h>
  29
  30#include <asm/tlbflush.h>
  31#include <asm/mmu_context.h>
  32
  33mm_context_t next_mmu_context;
  34unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
  35atomic_t nr_free_contexts;
  36struct mm_struct *context_mm[LAST_CONTEXT+1];
  37
  38/*
  39 * Initialize the context management stuff.
  40 */
  41void __init mmu_context_init(void)
  42{
  43        /*
  44         * The use of context zero is reserved for the kernel.
  45         * This code assumes FIRST_CONTEXT < 32.
  46         */
  47        context_map[0] = (1 << FIRST_CONTEXT) - 1;
  48        next_mmu_context = FIRST_CONTEXT;
  49        atomic_set(&nr_free_contexts, LAST_CONTEXT - FIRST_CONTEXT + 1);
  50}
  51
  52/*
  53 * Steal a context from a task that has one at the moment.
  54 *
  55 * This isn't an LRU system, it just frees up each context in
  56 * turn (sort-of pseudo-random replacement :).  This would be the
  57 * place to implement an LRU scheme if anyone were motivated to do it.
  58 */
  59void steal_context(void)
  60{
  61        struct mm_struct *mm;
  62
  63        /* free up context `next_mmu_context' */
  64        /* if we shouldn't free context 0, don't... */
  65        if (next_mmu_context < FIRST_CONTEXT)
  66                next_mmu_context = FIRST_CONTEXT;
  67        mm = context_mm[next_mmu_context];
  68        flush_tlb_mm(mm);
  69        destroy_context(mm);
  70}
  71