arch/avr32/include/asm/mmu_context.h

   1 /*
   2  * Copyright (C) 2004-2006 Atmel Corporation
   3  *
   4  * ASID handling taken from SH implementation.
   5  *   Copyright (C) 1999 Niibe Yutaka
   6  *   Copyright (C) 2003 Paul Mundt
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12 #ifndef __ASM_AVR32_MMU_CONTEXT_H
  13 #define __ASM_AVR32_MMU_CONTEXT_H
  14
  15 #include <asm/tlbflush.h>
  16 #include <asm/sysreg.h>
  17 #include <asm-generic/mm_hooks.h>
  18
  19 /*
  20  * The MMU "context" consists of two things:
  21  *    (a) TLB cache version
  22  *    (b) ASID (Address Space IDentifier)
  23  */
  24 #define MMU_CONTEXT_ASID_MASK           0x000000ff
  25 #define MMU_CONTEXT_VERSION_MASK        0xffffff00
  26 #define MMU_CONTEXT_FIRST_VERSION       0x00000100
  27 #define NO_CONTEXT                      0
  28
  29 #define MMU_NO_ASID                     0x100
  30
  31 /* Virtual Page Number mask */
  32 #define MMU_VPN_MASK    0xfffff000
  33
  34 /* Cache of MMU context last used */
  35 extern unsigned long mmu_context_cache;
  36
  37 /*
  38  * Get MMU context if needed
  39  */
  40 static inline void
  41 get_mmu_context(struct mm_struct *mm)
  42 {
  43         unsigned long mc = mmu_context_cache;
  44
  45         if (((mm->context ^ mc) & MMU_CONTEXT_VERSION_MASK) == 0)
  46                 /* It's up to date, do nothing */
  47                 return;
  48
  49         /* It's old, we need to get new context with new version */
  50         mc = ++mmu_context_cache;
  51         if (!(mc & MMU_CONTEXT_ASID_MASK)) {
  52                 /*
  53                  * We have exhausted all ASIDs of this version.
  54                  * Flush the TLB and start new cycle.
  55                  */
  56                 flush_tlb_all();
  57                 /*
  58                  * Fix version. Note that we avoid version #0
  59                  * to distinguish NO_CONTEXT.
  60                  */
  61                 if (!mc)
  62                         mmu_context_cache = mc = MMU_CONTEXT_FIRST_VERSION;
  63         }
  64         mm->context = mc;
  65 }
  66
  67 /*
  68  * Initialize the context related info for a new mm_struct
  69  * instance.
  70  */
  71 static inline int init_new_context(struct task_struct *tsk,
  72                                        struct mm_struct *mm)
  73 {
  74         mm->context = NO_CONTEXT;
  75         return 0;
  76 }
  77
  78 /*
  79  * Destroy context related info for an mm_struct that is about
  80  * to be put to rest.
  81  */
  82 static inline void destroy_context(struct mm_struct *mm)
  83 {
  84         /* Do nothing */
  85 }
  86
  87 static inline void set_asid(unsigned long asid)
  88 {
  89         /* XXX: We're destroying TLBEHI[8:31] */
  90         sysreg_write(TLBEHI, asid & MMU_CONTEXT_ASID_MASK);
  91         cpu_sync_pipeline();
  92 }
  93
  94 static inline unsigned long get_asid(void)
  95 {
  96         unsigned long asid;
  97
  98         asid = sysreg_read(TLBEHI);
  99         return asid & MMU_CONTEXT_ASID_MASK;
 100 }
 101
 102 static inline void activate_context(struct mm_struct *mm)
 103 {
 104         get_mmu_context(mm);
 105         set_asid(mm->context & MMU_CONTEXT_ASID_MASK);
 106 }
 107
 108 static inline void switch_mm(struct mm_struct *prev,
 109                                  struct mm_struct *next,
 110                                  struct task_struct *tsk)
 111 {
 112         if (likely(prev != next)) {
 113                 unsigned long __pgdir = (unsigned long)next->pgd;
 114
 115                 sysreg_write(PTBR, __pgdir);
 116                 activate_context(next);
 117         }
 118 }
 119
 120 #define deactivate_mm(tsk,mm) do { } while(0)
 121
 122 #define activate_mm(prev, next) switch_mm((prev), (next), NULL)
 123
 124 static inline void
 125 enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
 126 {
 127 }
 128
 129
 130 static inline void enable_mmu(void)
 131 {
 132         sysreg_write(MMUCR, (SYSREG_BIT(MMUCR_S)
 133                              | SYSREG_BIT(E)
 134                              | SYSREG_BIT(MMUCR_I)));
 135         nop(); nop(); nop(); nop(); nop(); nop(); nop(); nop();
 136
 137         if (mmu_context_cache == NO_CONTEXT)
 138                 mmu_context_cache = MMU_CONTEXT_FIRST_VERSION;
 139
 140         set_asid(mmu_context_cache & MMU_CONTEXT_ASID_MASK);
 141 }
 142
 143 static inline void disable_mmu(void)
 144 {
 145         sysreg_write(MMUCR, SYSREG_BIT(MMUCR_S));
 146 }
 147
 148 #endif /* __ASM_AVR32_MMU_CONTEXT_H */