text: /*
   *  linux/include/asm-arm/mmu_context.h
   *
   *  Copyright (C) 1996 Russell King.
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   *  Changelog:
   *   27-06-1996	RMK	Created
   */
  #ifndef __ASM_ARM_MMU_CONTEXT_H
  #define __ASM_ARM_MMU_CONTEXT_H
  
  #include <linux/compiler.h>
  #include <asm/cacheflush.h>
  #include <asm/proc-fns.h>
  
  void __check_kvm_seq(struct mm_struct *mm);
  
  #if __LINUX_ARM_ARCH__ >= 6
  
  /*
   * On ARMv6, we have the following structure in the Context ID:
   *
   * 31                         7          0
   * +-------------------------+-----------+
   * |      process ID         |   ASID    |
   * +-------------------------+-----------+
   * |              context ID             |
   * +-------------------------------------+
   *
   * The ASID is used to tag entries in the CPU caches and TLBs.
   * The context ID is used by debuggers and trace logic, and
   * should be unique within all running processes.
   */
  #define ASID_BITS	8
  #define ASID_MASK	((~0) << ASID_BITS)
  
  extern unsigned int cpu_last_asid;
  
  void __init_new_context(struct task_struct *tsk, struct mm_struct *mm);
  void __new_context(struct mm_struct *mm);
  
  static inline void check_context(struct mm_struct *mm)
  {
  	if (unlikely((mm->context.id ^ cpu_last_asid) >> ASID_BITS))
  		__new_context(mm);
  
  	if (unlikely(mm->context.kvm_seq != init_mm.context.kvm_seq))
  		__check_kvm_seq(mm);
  }
  
  #define init_new_context(tsk,mm)	(__init_new_context(tsk,mm),0)
  
  #else
  
  static inline void check_context(struct mm_struct *mm)
  {
  	if (unlikely(mm->context.kvm_seq != init_mm.context.kvm_seq))
  		__check_kvm_seq(mm);
  }
  
  #define init_new_context(tsk,mm)	0
  
  #endif
  
  #define destroy_context(mm)		do { } while(0)
  
  /*
   * This is called when "tsk" is about to enter lazy TLB mode.
   *
   * mm:  describes the currently active mm context
   * tsk: task which is entering lazy tlb
   * cpu: cpu number which is entering lazy tlb
   *
   * tsk->mm will be NULL
   */
  static inline void
  enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
  {
  }
  
  /*
   * This is the actual mm switch as far as the scheduler
   * is concerned.  No registers are touched.  We avoid
   * calling the CPU specific function when the mm hasn't
   * actually changed.
   */
  static inline void
  switch_mm(struct mm_struct *prev, struct mm_struct *next,
  	  struct task_struct *tsk)
  {
  #ifdef CONFIG_MMU
  	unsigned int cpu = smp_processor_id();
  
  	if (prev != next) {
  		cpu_set(cpu, next->cpu_vm_mask);
  		check_context(next);
  		cpu_switch_mm(next->pgd, next);
  		if (cache_is_vivt())
  			cpu_clear(cpu, prev->cpu_vm_mask);
  	}
  #endif
  }
  
  #define deactivate_mm(tsk,mm)	do { } while (0)
  #define activate_mm(prev,next)	switch_mm(prev, next, NULL)
  
  #endif
  