text: /*
   * Copyright (C) 2004-2006 Atmel Corporation
   *
   * ASID handling taken from SH implementation.
   *   Copyright (C) 1999 Niibe Yutaka
   *   Copyright (C) 2003 Paul Mundt
   *
   * 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.
   */
  #ifndef __ASM_AVR32_MMU_CONTEXT_H
  #define __ASM_AVR32_MMU_CONTEXT_H
  
  #include <linux/mm_types.h>
  
  #include <asm/tlbflush.h>
  #include <asm/sysreg.h>
  #include <asm-generic/mm_hooks.h>
  
  /*
   * The MMU "context" consists of two things:
   *    (a) TLB cache version
   *    (b) ASID (Address Space IDentifier)
   */
  #define MMU_CONTEXT_ASID_MASK		0x000000ff
  #define MMU_CONTEXT_VERSION_MASK	0xffffff00
  #define MMU_CONTEXT_FIRST_VERSION       0x00000100
  #define NO_CONTEXT			0
  
  #define MMU_NO_ASID			0x100
  
  /* Virtual Page Number mask */
  #define MMU_VPN_MASK	0xfffff000
  
  /* Cache of MMU context last used */
  extern unsigned long mmu_context_cache;
  
  /*
   * Get MMU context if needed
   */
  static inline void
  get_mmu_context(struct mm_struct *mm)
  {
  	unsigned long mc = mmu_context_cache;
  
  	if (((mm->context ^ mc) & MMU_CONTEXT_VERSION_MASK) == 0)
  		/* It's up to date, do nothing */
  		return;
  
  	/* It's old, we need to get new context with new version */
  	mc = ++mmu_context_cache;
  	if (!(mc & MMU_CONTEXT_ASID_MASK)) {
  		/*
  		 * We have exhausted all ASIDs of this version.
  		 * Flush the TLB and start new cycle.
  		 */
  		flush_tlb_all();
  		/*
  		 * Fix version. Note that we avoid version #0
  		 * to distinguish NO_CONTEXT.
  		 */
  		if (!mc)
  			mmu_context_cache = mc = MMU_CONTEXT_FIRST_VERSION;
  	}
  	mm->context = mc;
  }
  
  /*
   * Initialize the context related info for a new mm_struct
   * instance.
   */
  static inline int init_new_context(struct task_struct *tsk,
  				       struct mm_struct *mm)
  {
  	mm->context = NO_CONTEXT;
  	return 0;
  }
  
  /*
   * Destroy context related info for an mm_struct that is about
   * to be put to rest.
   */
  static inline void destroy_context(struct mm_struct *mm)
  {
  	/* Do nothing */
  }
  
  static inline void set_asid(unsigned long asid)
  {
  	/* XXX: We're destroying TLBEHI[8:31] */
  	sysreg_write(TLBEHI, asid & MMU_CONTEXT_ASID_MASK);
  	cpu_sync_pipeline();
  }
  
  static inline unsigned long get_asid(void)
  {
  	unsigned long asid;
  
  	asid = sysreg_read(TLBEHI);
  	return asid & MMU_CONTEXT_ASID_MASK;
  }
  
  static inline void activate_context(struct mm_struct *mm)
  {
  	get_mmu_context(mm);
  	set_asid(mm->context & MMU_CONTEXT_ASID_MASK);
  }
  
  static inline void switch_mm(struct mm_struct *prev,
  				 struct mm_struct *next,
  				 struct task_struct *tsk)
  {
  	if (likely(prev != next)) {
  		unsigned long __pgdir = (unsigned long)next->pgd;
  
  		sysreg_write(PTBR, __pgdir);
  		activate_context(next);
  	}
  }
  
  #define deactivate_mm(tsk,mm) do { } while(0)
  
  #define activate_mm(prev, next) switch_mm((prev), (next), NULL)
  
  static inline void
  enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
  {
  }
  
  
  static inline void enable_mmu(void)
  {
  	sysreg_write(MMUCR, (SYSREG_BIT(MMUCR_S)
  			     | SYSREG_BIT(E)
  			     | SYSREG_BIT(MMUCR_I)));
  	nop(); nop(); nop(); nop(); nop(); nop(); nop(); nop();
  
  	if (mmu_context_cache == NO_CONTEXT)
  		mmu_context_cache = MMU_CONTEXT_FIRST_VERSION;
  
  	set_asid(mmu_context_cache & MMU_CONTEXT_ASID_MASK);
  }
  
  static inline void disable_mmu(void)
  {
  	sysreg_write(MMUCR, SYSREG_BIT(MMUCR_S));
  }
  
  #endif /* __ASM_AVR32_MMU_CONTEXT_H */
  