1 /*
2 * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
3 * Copyright (C) 2008-2009 PetaLogix
4 * Copyright (C) 2006 Atmark Techno, Inc.
5 *
6 * This file is subject to the terms and conditions of the GNU General Public
7 * License. See the file "COPYING" in the main directory of this archive
8 * for more details.
9 */
10
11 #ifndef _ASM_MICROBLAZE_MMU_CONTEXT_H
12 #define _ASM_MICROBLAZE_MMU_CONTEXT_H
13
14 #include <linux/atomic.h>
15 #include <linux/mm_types.h>
16 #include <linux/sched.h>
17
18 #include <asm/bitops.h>
19 #include <asm/mmu.h>
20 #include <asm-generic/mm_hooks.h>
21
22 # ifdef __KERNEL__
23 /*
24 * This function defines the mapping from contexts to VSIDs (virtual
25 * segment IDs). We use a skew on both the context and the high 4 bits
26 * of the 32-bit virtual address (the "effective segment ID") in order
27 * to spread out the entries in the MMU hash table.
28 */
29 # define CTX_TO_VSID(ctx, va) (((ctx) * (897 * 16) + ((va) >> 28) * 0x111) \
30 & 0xffffff)
31
32 /*
33 MicroBlaze has 256 contexts, so we can just rotate through these
34 as a way of "switching" contexts. If the TID of the TLB is zero,
35 the PID/TID comparison is disabled, so we can use a TID of zero
36 to represent all kernel pages as shared among all contexts.
37 */
38
39 static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
40 {
41 }
42
43 # define NO_CONTEXT 256
44 # define LAST_CONTEXT 255
45 # define FIRST_CONTEXT 1
46
47 /*
48 * Set the current MMU context.
49 * This is done byloading up the segment registers for the user part of the
50 * address space.
51 *
52 * Since the PGD is immediately available, it is much faster to simply
53 * pass this along as a second parameter, which is required for 8xx and
54 * can be used for debugging on all processors (if you happen to have
55 * an Abatron).
56 */
57 extern void set_context(mm_context_t context, pgd_t *pgd);
58
59 /*
60 * Bitmap of contexts in use.
61 * The size of this bitmap is LAST_CONTEXT + 1 bits.
62 */
63 extern unsigned long context_map[];
64
65 /*
66 * This caches the next context number that we expect to be free.
67 * Its use is an optimization only, we can't rely on this context
68 * number to be free, but it usually will be.
69 */
70 extern mm_context_t next_mmu_context;
71
72 /*
73 * Since we don't have sufficient contexts to give one to every task
74 * that could be in the system, we need to be able to steal contexts.
75 * These variables support that.
76 */
77 extern atomic_t nr_free_contexts;
78 extern struct mm_struct *context_mm[LAST_CONTEXT+1];
79 extern void steal_context(void);
80
81 /*
82 * Get a new mmu context for the address space described by `mm'.
83 */
84 static inline void get_mmu_context(struct mm_struct *mm)
85 {
86 mm_context_t ctx;
87
88 if (mm->context != NO_CONTEXT)
89 return;
90 while (atomic_dec_if_positive(&nr_free_contexts) < 0)
91 steal_context();
92 ctx = next_mmu_context;
93 while (test_and_set_bit(ctx, context_map)) {
94 ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx);
95 if (ctx > LAST_CONTEXT)
96 ctx = 0;
97 }
98 next_mmu_context = (ctx + 1) & LAST_CONTEXT;
99 mm->context = ctx;
100 context_mm[ctx] = mm;
101 }
102
103 /*
104 * Set up the context for a new address space.
105 */
106 # define init_new_context(tsk, mm) (((mm)->context = NO_CONTEXT), 0)
107
108 /*
109 * We're finished using the context for an address space.
110 */
111 static inline void destroy_context(struct mm_struct *mm)
112 {
113 if (mm->context != NO_CONTEXT) {
114 clear_bit(mm->context, context_map);
115 mm->context = NO_CONTEXT;
116 atomic_inc(&nr_free_contexts);
117 }
118 }
119
120 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
121 struct task_struct *tsk)
122 {
123 tsk->thread.pgdir = next->pgd;
124 get_mmu_context(next);
125 set_context(next->context, next->pgd);
126 }
127
128 /*
129 * After we have set current->mm to a new value, this activates
130 * the context for the new mm so we see the new mappings.
131 */
132 static inline void activate_mm(struct mm_struct *active_mm,
133 struct mm_struct *mm)
134 {
135 current->thread.pgdir = mm->pgd;
136 get_mmu_context(mm);
137 set_context(mm->context, mm->pgd);
138 }
139
140 extern void mmu_context_init(void);
141
142 # endif /* __KERNEL__ */
143 #endif /* _ASM_MICROBLAZE_MMU_CONTEXT_H */