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/* MN10300 MMU context management
*
* Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
* Modified by David Howells (dhowells@redhat.com)
* - Derived from include/asm-m32r/mmu_context.h
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public Licence
* as published by the Free Software Foundation; either version
* 2 of the Licence, or (at your option) any later version.
*
*
* This implements an algorithm to provide TLB PID mappings to provide
* selective access to the TLB for processes, thus reducing the number of TLB
* flushes required.
*
* Note, however, that the M32R algorithm is technically broken as it does not
* handle version wrap-around, and could, theoretically, have a problem with a
* very long lived program that sleeps long enough for the version number to
* wrap all the way around so that its TLB mappings appear valid once again.
*/
#ifndef _ASM_MMU_CONTEXT_H
#define _ASM_MMU_CONTEXT_H
#include <asm/atomic.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#include <asm-generic/mm_hooks.h>
#define MMU_CONTEXT_TLBPID_NR 256
#define MMU_CONTEXT_TLBPID_MASK 0x000000ffUL
#define MMU_CONTEXT_VERSION_MASK 0xffffff00UL
#define MMU_CONTEXT_FIRST_VERSION 0x00000100UL
#define MMU_NO_CONTEXT 0x00000000UL
#define MMU_CONTEXT_TLBPID_LOCK_NR 0
#define enter_lazy_tlb(mm, tsk) do {} while (0)
#ifdef CONFIG_MN10300_TLB_USE_PIDR
extern unsigned long mmu_context_cache[NR_CPUS];
#define mm_context(mm) (mm->context.tlbpid[smp_processor_id()])
/**
* allocate_mmu_context - Allocate storage for the arch-specific MMU data
* @mm: The userspace VM context being set up
*/
static inline unsigned long allocate_mmu_context(struct mm_struct *mm)
{
unsigned long *pmc = &mmu_context_cache[smp_processor_id()];
unsigned long mc = ++(*pmc);
if (!(mc & MMU_CONTEXT_TLBPID_MASK)) {
/* we exhausted the TLB PIDs of this version on this CPU, so we
* flush this CPU's TLB in its entirety and start new cycle */
local_flush_tlb_all();
/* fix the TLB version if needed (we avoid version #0 so as to
* distingush MMU_NO_CONTEXT) */
if (!mc)
*pmc = mc = MMU_CONTEXT_FIRST_VERSION;
}
mm_context(mm) = mc;
return mc;
}
/*
* get an MMU context if one is needed
*/
static inline unsigned long get_mmu_context(struct mm_struct *mm)
{
unsigned long mc = MMU_NO_CONTEXT, cache;
if (mm) {
cache = mmu_context_cache[smp_processor_id()];
mc = mm_context(mm);
/* if we have an old version of the context, replace it */
if ((mc ^ cache) & MMU_CONTEXT_VERSION_MASK)
mc = allocate_mmu_context(mm);
}
return mc;
}
/*
* initialise 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 num_cpus = NR_CPUS, i;
for (i = 0; i < num_cpus; i++)
mm->context.tlbpid[i] = MMU_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)
{
PIDR = get_mmu_context(mm) & MMU_CONTEXT_TLBPID_MASK;
}
#else /* CONFIG_MN10300_TLB_USE_PIDR */
#define init_new_context(tsk, mm) (0)
#define activate_context(mm) local_flush_tlb()
#endif /* CONFIG_MN10300_TLB_USE_PIDR */
/**
* destroy_context - Destroy mm context information
* @mm: The MM being destroyed.
*
* Destroy context related info for an mm_struct that is about to be put to
* rest
*/
#define destroy_context(mm) do {} while (0)
/**
* switch_mm - Change between userspace virtual memory contexts
* @prev: The outgoing MM context.
* @next: The incoming MM context.
* @tsk: The incoming task.
*/
static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
struct task_struct *tsk)
{
if (prev != next) {
PTBR = (unsigned long) next->pgd;
activate_context(next);
}
}
#define deactivate_mm(tsk, mm) do {} while (0)
#define activate_mm(prev, next) switch_mm((prev), (next), NULL)
#endif /* _ASM_MMU_CONTEXT_H */
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