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