arch/microblaze/include/asm/mmu_context_mm.h

   1 /*
   2  * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
   3  * Copyright (C) 2008-2009 PetaLogix
   4  * Copyright (C) 2006 Atmark Techno, Inc.
   5  *
   6  * This file is subject to the terms and conditions of the GNU General Public
   7  * License. See the file "COPYING" in the main directory of this archive
   8  * for more details.
   9  */
  10
  11 #ifndef _ASM_MICROBLAZE_MMU_CONTEXT_H
  12 #define _ASM_MICROBLAZE_MMU_CONTEXT_H
  13
  14 #include <linux/atomic.h>
  15 #include <linux/mm_types.h>
  16 #include <linux/sched.h>
  17
  18 #include <asm/bitops.h>
  19 #include <asm/mmu.h>
  20 #include <asm-generic/mm_hooks.h>
  21
  22 # ifdef __KERNEL__
  23 /*
  24  * This function defines the mapping from contexts to VSIDs (virtual
  25  * segment IDs).  We use a skew on both the context and the high 4 bits
  26  * of the 32-bit virtual address (the "effective segment ID") in order
  27  * to spread out the entries in the MMU hash table.
  28  */
  29 # define CTX_TO_VSID(ctx, va)   (((ctx) * (897 * 16) + ((va) >> 28) * 0x111) \
  30                                  & 0xffffff)
  31
  32 /*
  33    MicroBlaze has 256 contexts, so we can just rotate through these
  34    as a way of "switching" contexts.  If the TID of the TLB is zero,
  35    the PID/TID comparison is disabled, so we can use a TID of zero
  36    to represent all kernel pages as shared among all contexts.
  37  */
  38
  39 static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
  40 {
  41 }
  42
  43 # define NO_CONTEXT     256
  44 # define LAST_CONTEXT   255
  45 # define FIRST_CONTEXT  1
  46
  47 /*
  48  * Set the current MMU context.
  49  * This is done byloading up the segment registers for the user part of the
  50  * address space.
  51  *
  52  * Since the PGD is immediately available, it is much faster to simply
  53  * pass this along as a second parameter, which is required for 8xx and
  54  * can be used for debugging on all processors (if you happen to have
  55  * an Abatron).
  56  */
  57 extern void set_context(mm_context_t context, pgd_t *pgd);
  58
  59 /*
  60  * Bitmap of contexts in use.
  61  * The size of this bitmap is LAST_CONTEXT + 1 bits.
  62  */
  63 extern unsigned long context_map[];
  64
  65 /*
  66  * This caches the next context number that we expect to be free.
  67  * Its use is an optimization only, we can't rely on this context
  68  * number to be free, but it usually will be.
  69  */
  70 extern mm_context_t next_mmu_context;
  71
  72 /*
  73  * Since we don't have sufficient contexts to give one to every task
  74  * that could be in the system, we need to be able to steal contexts.
  75  * These variables support that.
  76  */
  77 extern atomic_t nr_free_contexts;
  78 extern struct mm_struct *context_mm[LAST_CONTEXT+1];
  79 extern void steal_context(void);
  80
  81 /*
  82  * Get a new mmu context for the address space described by `mm'.
  83  */
  84 static inline void get_mmu_context(struct mm_struct *mm)
  85 {
  86         mm_context_t ctx;
  87
  88         if (mm->context != NO_CONTEXT)
  89                 return;
  90         while (atomic_dec_if_positive(&nr_free_contexts) < 0)
  91                 steal_context();
  92         ctx = next_mmu_context;
  93         while (test_and_set_bit(ctx, context_map)) {
  94                 ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx);
  95                 if (ctx > LAST_CONTEXT)
  96                         ctx = 0;
  97         }
  98         next_mmu_context = (ctx + 1) & LAST_CONTEXT;
  99         mm->context = ctx;
 100         context_mm[ctx] = mm;
 101 }
 102
 103 /*
 104  * Set up the context for a new address space.
 105  */
 106 # define init_new_context(tsk, mm)      (((mm)->context = NO_CONTEXT), 0)
 107
 108 /*
 109  * We're finished using the context for an address space.
 110  */
 111 static inline void destroy_context(struct mm_struct *mm)
 112 {
 113         if (mm->context != NO_CONTEXT) {
 114                 clear_bit(mm->context, context_map);
 115                 mm->context = NO_CONTEXT;
 116                 atomic_inc(&nr_free_contexts);
 117         }
 118 }
 119
 120 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
 121                              struct task_struct *tsk)
 122 {
 123         tsk->thread.pgdir = next->pgd;
 124         get_mmu_context(next);
 125         set_context(next->context, next->pgd);
 126 }
 127
 128 /*
 129  * After we have set current->mm to a new value, this activates
 130  * the context for the new mm so we see the new mappings.
 131  */
 132 static inline void activate_mm(struct mm_struct *active_mm,
 133                         struct mm_struct *mm)
 134 {
 135         current->thread.pgdir = mm->pgd;
 136         get_mmu_context(mm);
 137         set_context(mm->context, mm->pgd);
 138 }
 139
 140 extern void mmu_context_init(void);
 141
 142 # endif /* __KERNEL__ */
 143 #endif /* _ASM_MICROBLAZE_MMU_CONTEXT_H */