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mmu_context.h

/*
 * Copyright (C) 1999 Niibe Yutaka
 * Copyright (C) 2003 - 2007 Paul Mundt
 *
 * ASID handling idea taken from MIPS implementation.
 */
#ifndef __ASM_SH_MMU_CONTEXT_H
#define __ASM_SH_MMU_CONTEXT_H

#ifdef __KERNEL__
#include <cpu/mmu_context.h>
#include <asm/tlbflush.h>
#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm-generic/mm_hooks.h>

/*
 * The MMU "context" consists of two things:
 *    (a) TLB cache version (or round, cycle whatever expression you like)
 *    (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

/* ASID is 8-bit value, so it can't be 0x100 */
#define MMU_NO_ASID                 0x100

#define asid_cache(cpu)       (cpu_data[cpu].asid_cache)

#ifdef CONFIG_MMU
#define cpu_context(cpu, mm)  ((mm)->context.id[cpu])

#define cpu_asid(cpu, mm)     \
      (cpu_context((cpu), (mm)) & MMU_CONTEXT_ASID_MASK)

/*
 * Virtual Page Number mask
 */
#define MMU_VPN_MASK    0xfffff000

#if defined(CONFIG_SUPERH32)
#include "mmu_context_32.h"
#else
#include "mmu_context_64.h"
#endif

/*
 * Get MMU context if needed.
 */
static inline void get_mmu_context(struct mm_struct *mm, unsigned int cpu)
{
      unsigned long asid = asid_cache(cpu);

      /* Check if we have old version of context. */
      if (((cpu_context(cpu, mm) ^ asid) & 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. */
      if (!(++asid & MMU_CONTEXT_ASID_MASK)) {
            /*
             * We exhaust ASID of this version.
             * Flush all TLB and start new cycle.
             */
            flush_tlb_all();

#ifdef CONFIG_SUPERH64
            /*
             * The SH-5 cache uses the ASIDs, requiring both the I and D
             * cache to be flushed when the ASID is exhausted. Weak.
             */
            flush_cache_all();
#endif

            /*
             * Fix version; Note that we avoid version #0
             * to distingush NO_CONTEXT.
             */
            if (!asid)
                  asid = MMU_CONTEXT_FIRST_VERSION;
      }

      cpu_context(cpu, mm) = asid_cache(cpu) = asid;
}

/*
 * 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)
{
      int i;

      for (i = 0; i < num_online_cpus(); i++)
            cpu_context(i, mm) = NO_CONTEXT;

      return 0;
}

/*
 * After we have set current->mm to a new value, this activates
 * the context for the new mm so we see the new mappings.
 */
static inline void activate_context(struct mm_struct *mm, unsigned int cpu)
{
      get_mmu_context(mm, cpu);
      set_asid(cpu_asid(cpu, mm));
}

static inline void switch_mm(struct mm_struct *prev,
                       struct mm_struct *next,
                       struct task_struct *tsk)
{
      unsigned int cpu = smp_processor_id();

      if (likely(prev != next)) {
            cpu_set(cpu, next->cpu_vm_mask);
            set_TTB(next->pgd);
            activate_context(next, cpu);
      } else
            if (!cpu_test_and_set(cpu, next->cpu_vm_mask))
                  activate_context(next, cpu);
}
#else
#define get_mmu_context(mm)         do { } while (0)
#define init_new_context(tsk,mm)    (0)
#define destroy_context(mm)         do { } while (0)
#define set_asid(asid)              do { } while (0)
#define get_asid()                  (0)
#define cpu_asid(cpu, mm)           ({ (void)cpu; 0; })
#define switch_and_save_asid(asid)  (0)
#define set_TTB(pgd)                do { } while (0)
#define get_TTB()             (0)
#define activate_context(mm,cpu)    do { } while (0)
#define switch_mm(prev,next,tsk)    do { } while (0)
#endif /* CONFIG_MMU */

#define activate_mm(prev, next)           switch_mm((prev),(next),NULL)
#define deactivate_mm(tsk,mm)       do { } while (0)
#define enter_lazy_tlb(mm,tsk)            do { } while (0)

#if defined(CONFIG_CPU_SH3) || defined(CONFIG_CPU_SH4)
/*
 * If this processor has an MMU, we need methods to turn it off/on ..
 * paging_init() will also have to be updated for the processor in
 * question.
 */
static inline void enable_mmu(void)
{
      unsigned int cpu = smp_processor_id();

      /* Enable MMU */
      ctrl_outl(MMU_CONTROL_INIT, MMUCR);
      ctrl_barrier();

      if (asid_cache(cpu) == NO_CONTEXT)
            asid_cache(cpu) = MMU_CONTEXT_FIRST_VERSION;

      set_asid(asid_cache(cpu) & MMU_CONTEXT_ASID_MASK);
}

static inline void disable_mmu(void)
{
      unsigned long cr;

      cr = ctrl_inl(MMUCR);
      cr &= ~MMU_CONTROL_INIT;
      ctrl_outl(cr, MMUCR);

      ctrl_barrier();
}
#else
/*
 * MMU control handlers for processors lacking memory
 * management hardware.
 */
#define enable_mmu()    do { } while (0)
#define disable_mmu()   do { } while (0)
#endif

#endif /* __KERNEL__ */
#endif /* __ASM_SH_MMU_CONTEXT_H */

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