Linux 2.6.26-rc5
[linux-2.6/openmoko-kernel/knife-kernel.git] / include / asm-mn10300 / mmu_context.h
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1 /* MN10300 MMU context management
3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4 * Modified by David Howells (dhowells@redhat.com)
5 * - Derived from include/asm-m32r/mmu_context.h
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public Licence
9 * as published by the Free Software Foundation; either version
10 * 2 of the Licence, or (at your option) any later version.
13 * This implements an algorithm to provide TLB PID mappings to provide
14 * selective access to the TLB for processes, thus reducing the number of TLB
15 * flushes required.
17 * Note, however, that the M32R algorithm is technically broken as it does not
18 * handle version wrap-around, and could, theoretically, have a problem with a
19 * very long lived program that sleeps long enough for the version number to
20 * wrap all the way around so that its TLB mappings appear valid once again.
22 #ifndef _ASM_MMU_CONTEXT_H
23 #define _ASM_MMU_CONTEXT_H
25 #include <asm/atomic.h>
26 #include <asm/pgalloc.h>
27 #include <asm/tlbflush.h>
28 #include <asm-generic/mm_hooks.h>
30 #define MMU_CONTEXT_TLBPID_MASK 0x000000ffUL
31 #define MMU_CONTEXT_VERSION_MASK 0xffffff00UL
32 #define MMU_CONTEXT_FIRST_VERSION 0x00000100UL
33 #define MMU_NO_CONTEXT 0x00000000UL
35 extern unsigned long mmu_context_cache[NR_CPUS];
36 #define mm_context(mm) (mm->context.tlbpid[smp_processor_id()])
38 #define enter_lazy_tlb(mm, tsk) do {} while (0)
40 #ifdef CONFIG_SMP
41 #define cpu_ran_vm(cpu, task) \
42 cpu_set((cpu), (task)->cpu_vm_mask)
43 #define cpu_maybe_ran_vm(cpu, task) \
44 cpu_test_and_set((cpu), (task)->cpu_vm_mask)
45 #else
46 #define cpu_ran_vm(cpu, task) do {} while (0)
47 #define cpu_maybe_ran_vm(cpu, task) true
48 #endif /* CONFIG_SMP */
51 * allocate an MMU context
53 static inline unsigned long allocate_mmu_context(struct mm_struct *mm)
55 unsigned long *pmc = &mmu_context_cache[smp_processor_id()];
56 unsigned long mc = ++(*pmc);
58 if (!(mc & MMU_CONTEXT_TLBPID_MASK)) {
59 /* we exhausted the TLB PIDs of this version on this CPU, so we
60 * flush this CPU's TLB in its entirety and start new cycle */
61 flush_tlb_all();
63 /* fix the TLB version if needed (we avoid version #0 so as to
64 * distingush MMU_NO_CONTEXT) */
65 if (!mc)
66 *pmc = mc = MMU_CONTEXT_FIRST_VERSION;
68 mm_context(mm) = mc;
69 return mc;
73 * get an MMU context if one is needed
75 static inline unsigned long get_mmu_context(struct mm_struct *mm)
77 unsigned long mc = MMU_NO_CONTEXT, cache;
79 if (mm) {
80 cache = mmu_context_cache[smp_processor_id()];
81 mc = mm_context(mm);
83 /* if we have an old version of the context, replace it */
84 if ((mc ^ cache) & MMU_CONTEXT_VERSION_MASK)
85 mc = allocate_mmu_context(mm);
87 return mc;
91 * initialise the context related info for a new mm_struct instance
93 static inline int init_new_context(struct task_struct *tsk,
94 struct mm_struct *mm)
96 int num_cpus = NR_CPUS, i;
98 for (i = 0; i < num_cpus; i++)
99 mm->context.tlbpid[i] = MMU_NO_CONTEXT;
100 return 0;
104 * destroy context related info for an mm_struct that is about to be put to
105 * rest
107 #define destroy_context(mm) do { } while (0)
110 * after we have set current->mm to a new value, this activates the context for
111 * the new mm so we see the new mappings.
113 static inline void activate_context(struct mm_struct *mm, int cpu)
115 PIDR = get_mmu_context(mm) & MMU_CONTEXT_TLBPID_MASK;
119 * change between virtual memory sets
121 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
122 struct task_struct *tsk)
124 int cpu = smp_processor_id();
126 if (prev != next) {
127 cpu_ran_vm(cpu, next);
128 activate_context(next, cpu);
129 PTBR = (unsigned long) next->pgd;
130 } else if (!cpu_maybe_ran_vm(cpu, next)) {
131 activate_context(next, cpu);
135 #define deactivate_mm(tsk, mm) do {} while (0)
136 #define activate_mm(prev, next) switch_mm((prev), (next), NULL)
138 #endif /* _ASM_MMU_CONTEXT_H */