projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| ae3a197e DH |
1 | /* |
| 2 | * Copyright (C) 1999 Cort Dougan <cort@cs.nmt.edu> | |
| 3 | */ | |
| 4 | #ifndef _ASM_POWERPC_BARRIER_H | |
| 5 | #define _ASM_POWERPC_BARRIER_H | |
| 6 | ||
| 7 | /* | |
| 8 | * Memory barrier. | |
| 9 | * The sync instruction guarantees that all memory accesses initiated | |
| 10 | * by this processor have been performed (with respect to all other | |
| 11 | * mechanisms that access memory). The eieio instruction is a barrier | |
| 12 | * providing an ordering (separately) for (a) cacheable stores and (b) | |
| 13 | * loads and stores to non-cacheable memory (e.g. I/O devices). | |
| 14 | * | |
| 15 | * mb() prevents loads and stores being reordered across this point. | |
| 16 | * rmb() prevents loads being reordered across this point. | |
| 17 | * wmb() prevents stores being reordered across this point. | |
| 18 | * read_barrier_depends() prevents data-dependent loads being reordered | |
| 19 | * across this point (nop on PPC). | |
| 20 | * | |
| 21 | * *mb() variants without smp_ prefix must order all types of memory | |
| 22 | * operations with one another. sync is the only instruction sufficient | |
| 23 | * to do this. | |
| 24 | * | |
| 25 | * For the smp_ barriers, ordering is for cacheable memory operations | |
| 26 | * only. We have to use the sync instruction for smp_mb(), since lwsync | |
| 27 | * doesn't order loads with respect to previous stores. Lwsync can be | |
| 28 | * used for smp_rmb() and smp_wmb(). | |
| 29 | * | |
| 30 | * However, on CPUs that don't support lwsync, lwsync actually maps to a | |
| 31 | * heavy-weight sync, so smp_wmb() can be a lighter-weight eieio. | |
| 32 | */ | |
| 33 | #define mb() __asm__ __volatile__ ("sync" : : : "memory") | |
| 34 | #define rmb() __asm__ __volatile__ ("sync" : : : "memory") | |
| 35 | #define wmb() __asm__ __volatile__ ("sync" : : : "memory") | |
| 36 | #define read_barrier_depends() do { } while(0) | |
| 37 | ||
| 38 | #define set_mb(var, value) do { var = value; mb(); } while (0) | |
| 39 | ||
| 40 | #ifdef CONFIG_SMP | |
| 41 | ||
| 42 | #ifdef __SUBARCH_HAS_LWSYNC | |
| 43 | # define SMPWMB LWSYNC | |
| 44 | #else | |
| 45 | # define SMPWMB eieio | |
| 46 | #endif | |
| 47 | ||
| 48 | #define smp_mb() mb() | |
| 49 | #define smp_rmb() __asm__ __volatile__ (stringify_in_c(LWSYNC) : : :"memory") | |
| 50 | #define smp_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : : :"memory") | |
| 51 | #define smp_read_barrier_depends() read_barrier_depends() | |
| 52 | #else | |
| 53 | #define smp_mb() barrier() | |
| 54 | #define smp_rmb() barrier() | |
| 55 | #define smp_wmb() barrier() | |
| 56 | #define smp_read_barrier_depends() do { } while(0) | |
| 57 | #endif /* CONFIG_SMP */ | |
| 58 | ||
| 59 | /* | |
| 60 | * This is a barrier which prevents following instructions from being | |
| 61 | * started until the value of the argument x is known. For example, if | |
| 62 | * x is a variable loaded from memory, this prevents following | |
| 63 | * instructions from being executed until the load has been performed. | |
| 64 | */ | |
| 65 | #define data_barrier(x) \ | |
| 66 | asm volatile("twi 0,%0,0; isync" : : "r" (x) : "memory"); | |
| 67 | ||
| 68 | #endif /* _ASM_POWERPC_BARRIER_H */ |