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 
56 static inline void set_rasid_register (unsigned long val)
57 {
58 	__asm__ __volatile__ (" wsr %0, rasid\n\t"
59 			      " isync\n" : : "a" (val));
60 }
61 
62 static inline unsigned long get_rasid_register (void)
63 {
64 	unsigned long tmp;
65 	__asm__ __volatile__ (" rsr %0, rasid\n\t" : "=a" (tmp));
66 	return tmp;
67 }
68 
69 static inline void get_new_mmu_context(struct mm_struct *mm, unsigned int cpu)
70 {
71 	unsigned long asid = cpu_asid_cache(cpu);
72 	if ((++asid & ASID_MASK) == 0) {
73 		/*
74 		 * Start new asid cycle; continue counting with next
75 		 * incarnation bits; skipping over 0, 1, 2, 3.
76 		 */
77 		local_flush_tlb_all();
78 		asid += ASID_USER_FIRST;
79 	}
80 	cpu_asid_cache(cpu) = asid;
81 	mm->context.asid[cpu] = asid;
82 	mm->context.cpu = cpu;
83 }
84 
85 static inline void get_mmu_context(struct mm_struct *mm, unsigned int cpu)
86 {
87 	/*
88 	 * Check if our ASID is of an older version and thus invalid.
89 	 */
90 
91 	if (mm) {
92 		unsigned long asid = mm->context.asid[cpu];
93 
94 		if (asid == NO_CONTEXT ||
95 				((asid ^ cpu_asid_cache(cpu)) & ~ASID_MASK))
96 			get_new_mmu_context(mm, cpu);
97 	}
98 }
99 
100 static inline void activate_context(struct mm_struct *mm, unsigned int cpu)
101 {
102 	get_mmu_context(mm, cpu);
103 	set_rasid_register(ASID_INSERT(mm->context.asid[cpu]));
104 	invalidate_page_directory();
105 }
106 
107 /*
108  * Initialize the context related info for a new mm_struct
109  * instance.  Valid cpu values are 0..(NR_CPUS-1), so initializing
110  * to -1 says the process has never run on any core.
111  */
112 
113 static inline int init_new_context(struct task_struct *tsk,
114 		struct mm_struct *mm)
115 {
116 	int cpu;
117 	for_each_possible_cpu(cpu) {
118 		mm->context.asid[cpu] = NO_CONTEXT;
119 	}
120 	mm->context.cpu = -1;
121 	return 0;
122 }
123 
124 static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
125 			     struct task_struct *tsk)
126 {
127 	unsigned int cpu = smp_processor_id();
128 	int migrated = next->context.cpu != cpu;
129 	/* Flush the icache if we migrated to a new core. */
130 	if (migrated) {
131 		__invalidate_icache_all();
132 		next->context.cpu = cpu;
133 	}
134 	if (migrated || prev != next)
135 		activate_context(next, cpu);
136 }
137 
138 #define activate_mm(prev, next)	switch_mm((prev), (next), NULL)
139 #define deactivate_mm(tsk, mm)	do { } while (0)
140 
141 /*
142  * Destroy context related info for an mm_struct that is about
143  * to be put to rest.
144  */
145 static inline void destroy_context(struct mm_struct *mm)
146 {
147 	invalidate_page_directory();
148 }
149 
150 
151 static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
152 {
153 	/* Nothing to do. */
154 
155 }
156 
157 #endif /* CONFIG_MMU */
158 #endif /* _XTENSA_MMU_CONTEXT_H */
159