LXR linux/arch/nios2/mm/mmu

   1/*
   2 * MMU context handling.
   3 *
   4 * Copyright (C) 2011 Tobias Klauser <tklauser@distanz.ch>
   5 * Copyright (C) 2009 Wind River Systems Inc
   6 *   Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
   7 *
   8 * This file is subject to the terms and conditions of the GNU General Public
   9 * License.  See the file "COPYING" in the main directory of this archive
  10 * for more details.
  11 */
  12
  13#include <linux/mm.h>
  14
  15#include <asm/cpuinfo.h>
  16#include <asm/mmu_context.h>
  17#include <asm/tlb.h>
  18
  19/* The pids position and mask in context */
  20#define PID_SHIFT       0
  21#define PID_BITS        (cpuinfo.tlb_pid_num_bits)
  22#define PID_MASK        ((1UL << PID_BITS) - 1)
  23
  24/* The versions position and mask in context */
  25#define VERSION_BITS    (32 - PID_BITS)
  26#define VERSION_SHIFT   (PID_SHIFT + PID_BITS)
  27#define VERSION_MASK    ((1UL << VERSION_BITS) - 1)
  28
  29/* Return the version part of a context */
  30#define CTX_VERSION(c)  (((c) >> VERSION_SHIFT) & VERSION_MASK)
  31
  32/* Return the pid part of a context */
  33#define CTX_PID(c)      (((c) >> PID_SHIFT) & PID_MASK)
  34
  35/* Value of the first context (version 1, pid 0) */
  36#define FIRST_CTX       ((1UL << VERSION_SHIFT) | (0 << PID_SHIFT))
  37
  38static mm_context_t next_mmu_context;
  39
  40/*
  41 * Initialize MMU context management stuff.
  42 */
  43void __init mmu_context_init(void)
  44{
  45        /* We need to set this here because the value depends on runtime data
  46         * from cpuinfo */
  47        next_mmu_context = FIRST_CTX;
  48}
  49
  50/*
  51 * Set new context (pid), keep way
  52 */
  53static void set_context(mm_context_t context)
  54{
  55        set_mmu_pid(CTX_PID(context));
  56}
  57
  58static mm_context_t get_new_context(void)
  59{
  60        /* Return the next pid */
  61        next_mmu_context += (1UL << PID_SHIFT);
  62
  63        /* If the pid field wraps around we increase the version and
  64         * flush the tlb */
  65        if (unlikely(CTX_PID(next_mmu_context) == 0)) {
  66                /* Version is incremented since the pid increment above
  67                 * overflows info version */
  68                flush_cache_all();
  69                flush_tlb_all();
  70        }
  71
  72        /* If the version wraps we start over with the first generation, we do
  73         * not need to flush the tlb here since it's always done above */
  74        if (unlikely(CTX_VERSION(next_mmu_context) == 0))
  75                next_mmu_context = FIRST_CTX;
  76
  77        return next_mmu_context;
  78}
  79
  80void switch_mm(struct mm_struct *prev, struct mm_struct *next,
  81               struct task_struct *tsk)
  82{
  83        unsigned long flags;
  84
  85        local_irq_save(flags);
  86
  87        /* If the process context we are swapping in has a different context
  88         * generation then we have it should get a new generation/pid */
  89        if (unlikely(CTX_VERSION(next->context) !=
  90                CTX_VERSION(next_mmu_context)))
  91                next->context = get_new_context();
  92
  93        /* Save the current pgd so the fast tlb handler can find it */
  94        pgd_current = next->pgd;
  95
  96        /* Set the current context */
  97        set_context(next->context);
  98
  99        local_irq_restore(flags);
 100}
 101
 102/*
 103 * After we have set current->mm to a new value, this activates
 104 * the context for the new mm so we see the new mappings.
 105 */
 106void activate_mm(struct mm_struct *prev, struct mm_struct *next)
 107{
 108        next->context = get_new_context();
 109        set_context(next->context);
 110        pgd_current = next->pgd;
 111}
 112
 113unsigned long get_pid_from_context(mm_context_t *context)
 114{
 115        return CTX_PID((*context));
 116}
 117