xref: /openbmc/linux/include/asm-generic/barrier.h (revision e2f1cf25)
1 /*
2  * Generic barrier definitions, originally based on MN10300 definitions.
3  *
4  * It should be possible to use these on really simple architectures,
5  * but it serves more as a starting point for new ports.
6  *
7  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
8  * Written by David Howells (dhowells@redhat.com)
9  *
10  * This program is free software; you can redistribute it and/or
11  * modify it under the terms of the GNU General Public Licence
12  * as published by the Free Software Foundation; either version
13  * 2 of the Licence, or (at your option) any later version.
14  */
15 #ifndef __ASM_GENERIC_BARRIER_H
16 #define __ASM_GENERIC_BARRIER_H
17 
18 #ifndef __ASSEMBLY__
19 
20 #include <linux/compiler.h>
21 
22 #ifndef nop
23 #define nop()	asm volatile ("nop")
24 #endif
25 
26 /*
27  * Force strict CPU ordering. And yes, this is required on UP too when we're
28  * talking to devices.
29  *
30  * Fall back to compiler barriers if nothing better is provided.
31  */
32 
33 #ifndef mb
34 #define mb()	barrier()
35 #endif
36 
37 #ifndef rmb
38 #define rmb()	mb()
39 #endif
40 
41 #ifndef wmb
42 #define wmb()	mb()
43 #endif
44 
45 #ifndef dma_rmb
46 #define dma_rmb()	rmb()
47 #endif
48 
49 #ifndef dma_wmb
50 #define dma_wmb()	wmb()
51 #endif
52 
53 #ifndef read_barrier_depends
54 #define read_barrier_depends()		do { } while (0)
55 #endif
56 
57 #ifdef CONFIG_SMP
58 
59 #ifndef smp_mb
60 #define smp_mb()	mb()
61 #endif
62 
63 #ifndef smp_rmb
64 #define smp_rmb()	rmb()
65 #endif
66 
67 #ifndef smp_wmb
68 #define smp_wmb()	wmb()
69 #endif
70 
71 #ifndef smp_read_barrier_depends
72 #define smp_read_barrier_depends()	read_barrier_depends()
73 #endif
74 
75 #else	/* !CONFIG_SMP */
76 
77 #ifndef smp_mb
78 #define smp_mb()	barrier()
79 #endif
80 
81 #ifndef smp_rmb
82 #define smp_rmb()	barrier()
83 #endif
84 
85 #ifndef smp_wmb
86 #define smp_wmb()	barrier()
87 #endif
88 
89 #ifndef smp_read_barrier_depends
90 #define smp_read_barrier_depends()	do { } while (0)
91 #endif
92 
93 #endif	/* CONFIG_SMP */
94 
95 #ifndef smp_store_mb
96 #define smp_store_mb(var, value)  do { WRITE_ONCE(var, value); mb(); } while (0)
97 #endif
98 
99 #ifndef smp_mb__before_atomic
100 #define smp_mb__before_atomic()	smp_mb()
101 #endif
102 
103 #ifndef smp_mb__after_atomic
104 #define smp_mb__after_atomic()	smp_mb()
105 #endif
106 
107 #define smp_store_release(p, v)						\
108 do {									\
109 	compiletime_assert_atomic_type(*p);				\
110 	smp_mb();							\
111 	ACCESS_ONCE(*p) = (v);						\
112 } while (0)
113 
114 #define smp_load_acquire(p)						\
115 ({									\
116 	typeof(*p) ___p1 = ACCESS_ONCE(*p);				\
117 	compiletime_assert_atomic_type(*p);				\
118 	smp_mb();							\
119 	___p1;								\
120 })
121 
122 #endif /* !__ASSEMBLY__ */
123 #endif /* __ASM_GENERIC_BARRIER_H */
124