1 /*
2  * Switch an MMU context.
3  *
4  * This file is subject to the terms and conditions of the GNU General Public
5  * License.  See the file "COPYING" in the main directory of this archive
6  * for more details.
7  *
8  * Copyright (C) 2001 - 2013 Tensilica Inc.
9  */
10 
11 #ifndef _XTENSA_MMU_CONTEXT_H
12 #define _XTENSA_MMU_CONTEXT_H
13 
14 #ifndef CONFIG_MMU
15 #include <asm/nommu_context.h>
16 #else
17 
18 #include <linux/stringify.h>
19 #include <linux/sched.h>
20 #include <linux/mm_types.h>
21 
22 #include <asm/vectors.h>
23 
24 #include <asm/pgtable.h>
25 #include <asm/cacheflush.h>
26 #include <asm/tlbflush.h>
27 #include <asm-generic/mm_hooks.h>
28 #include <asm-generic/percpu.h>
29 
30 #if (XCHAL_HAVE_TLBS != 1)
31 # error "Linux must have an MMU!"
32 #endif
33 
34 DECLARE_PER_CPU(unsigned long, asid_cache);
35 #define cpu_asid_cache(cpu) per_cpu(asid_cache, cpu)
36 
37 /*
38  * NO_CONTEXT is the invalid ASID value that we don't ever assign to
39  * any user or kernel context.  We use the reserved values in the
40  * ASID_INSERT macro below.
41  *
42  * 0 invalid
43  * 1 kernel
44  * 2 reserved
45  * 3 reserved
46  * 4...255 available
47  */
48 
49 #define NO_CONTEXT	0
50 #define ASID_USER_FIRST	4
51 #define ASID_MASK	((1 << XCHAL_MMU_ASID_BITS) - 1)
52 #define ASID_INSERT(x)	(0x03020001 | (((x) & ASID_MASK) << 8))
53 
54 void init_mmu(void);
55 void init_kio(void);
56 
57 static inline void set_rasid_register (unsigned long val)
58 {
59 	__asm__ __volatile__ (" wsr %0, rasid\n\t"
60 			      " isync\n" : : "a" (val));
61 }
62 
63 static inline unsigned long get_rasid_register (void)
64 {
65 	unsigned long tmp;
66 	__asm__ __volatile__ (" rsr %0, rasid\n\t" : "=a" (tmp));
67 	return tmp;
68 }
69 
70 static inline void get_new_mmu_context(struct mm_struct *mm, unsigned int cpu)
71 {
72 	unsigned long asid = cpu_asid_cache(cpu);
73 	if ((++asid & ASID_MASK) == 0) {
74 		/*
75 		 * Start new asid cycle; continue counting with next
76 		 * incarnation bits; skipping over 0, 1, 2, 3.
77 		 */
78 		local_flush_tlb_all();
79 		asid += ASID_USER_FIRST;
80 	}
81 	cpu_asid_cache(cpu) = asid;
82 	mm->context.asid[cpu] = asid;
83 	mm->context.cpu = cpu;
84 }
85 
86 static inline void get_mmu_context(struct mm_struct *mm, unsigned int cpu)
87 {
88 	/*
89 	 * Check if our ASID is of an older version and thus invalid.
90 	 */
91 
92 	if (mm) {
93 		unsigned long asid = mm->context.asid[cpu];
94 
95 		if (asid == NO_CONTEXT ||
96 				((asid ^ cpu_asid_cache(cpu)) & ~ASID_MASK))
97 			get_new_mmu_context(mm, cpu);
98 	}
99 }
100 
101 static inline void activate_context(struct mm_struct *mm, unsigned int cpu)
102 {
103 	get_mmu_context(mm, cpu);
104 	set_rasid_register(ASID_INSERT(mm->context.asid[cpu]));
105 	invalidate_page_directory();
106 }
107 
108 /*
109  * Initialize the context related info for a new mm_struct
110  * instance.  Valid cpu values are 0..(NR_CPUS-1), so initializing
111  * to -1 says the process has never run on any core.
112  */
113 
114 static inline int init_new_context(struct task_struct *tsk,
115 		struct mm_struct *mm)
116 {
117 	int cpu;
118 	for_each_possible_cpu(cpu) {
119 		mm->context.asid[cpu] = NO_CONTEXT;
120 	}
121 	mm->context.cpu = -1;
122 	return 0;
123 }
124 
125 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
126 			     struct task_struct *tsk)
127 {
128 	unsigned int cpu = smp_processor_id();
129 	int migrated = next->context.cpu != cpu;
130 	/* Flush the icache if we migrated to a new core. */
131 	if (migrated) {
132 		__invalidate_icache_all();
133 		next->context.cpu = cpu;
134 	}
135 	if (migrated || prev != next)
136 		activate_context(next, cpu);
137 }
138 
139 #define activate_mm(prev, next)	switch_mm((prev), (next), NULL)
140 #define deactivate_mm(tsk, mm)	do { } while (0)
141 
142 /*
143  * Destroy context related info for an mm_struct that is about
144  * to be put to rest.
145  */
146 static inline void destroy_context(struct mm_struct *mm)
147 {
148 	invalidate_page_directory();
149 }
150 
151 
152 static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
153 {
154 	/* Nothing to do. */
155 
156 }
157 
158 #endif /* CONFIG_MMU */
159 #endif /* _XTENSA_MMU_CONTEXT_H */
160