arch/nios2/mm/mmu_context.c

   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
  38 static mm_context_t next_mmu_context;
  39
  40 /*
  41  * Initialize MMU context management stuff.
  42  */
  43 void __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  */
  53 static void set_context(mm_context_t context)
  54 {
  55         set_mmu_pid(CTX_PID(context));
  56 }
  57
  58 static 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
  80 void 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  */
 106 void 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
 113 unsigned long get_pid_from_context(mm_context_t *context)
 114 {
 115         return CTX_PID((*context));
 116 }