diff options
author | David Howells <dhowells@redhat.com> | 2012-03-28 18:30:02 +0100 |
---|---|---|
committer | David Howells <dhowells@redhat.com> | 2012-03-28 18:30:02 +0100 |
commit | ae3a197e3d0bfe3f4bf1693723e82dc018c096f3 (patch) | |
tree | 12a222c01afd73dbc3ebb6859952083e2eb96441 /arch/powerpc/include/asm/barrier.h | |
parent | 527dcdccd60759ee38e6224c93f87a6194d970ad (diff) | |
download | linux-ae3a197e3d0bfe3f4bf1693723e82dc018c096f3.tar.bz2 |
Disintegrate asm/system.h for PowerPC
Disintegrate asm/system.h for PowerPC.
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
cc: linuxppc-dev@lists.ozlabs.org
Diffstat (limited to 'arch/powerpc/include/asm/barrier.h')
-rw-r--r-- | arch/powerpc/include/asm/barrier.h | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/barrier.h b/arch/powerpc/include/asm/barrier.h new file mode 100644 index 000000000000..ae782254e731 --- /dev/null +++ b/arch/powerpc/include/asm/barrier.h @@ -0,0 +1,68 @@ +/* + * Copyright (C) 1999 Cort Dougan <cort@cs.nmt.edu> + */ +#ifndef _ASM_POWERPC_BARRIER_H +#define _ASM_POWERPC_BARRIER_H + +/* + * Memory barrier. + * The sync instruction guarantees that all memory accesses initiated + * by this processor have been performed (with respect to all other + * mechanisms that access memory). The eieio instruction is a barrier + * providing an ordering (separately) for (a) cacheable stores and (b) + * loads and stores to non-cacheable memory (e.g. I/O devices). + * + * mb() prevents loads and stores being reordered across this point. + * rmb() prevents loads being reordered across this point. + * wmb() prevents stores being reordered across this point. + * read_barrier_depends() prevents data-dependent loads being reordered + * across this point (nop on PPC). + * + * *mb() variants without smp_ prefix must order all types of memory + * operations with one another. sync is the only instruction sufficient + * to do this. + * + * For the smp_ barriers, ordering is for cacheable memory operations + * only. We have to use the sync instruction for smp_mb(), since lwsync + * doesn't order loads with respect to previous stores. Lwsync can be + * used for smp_rmb() and smp_wmb(). + * + * However, on CPUs that don't support lwsync, lwsync actually maps to a + * heavy-weight sync, so smp_wmb() can be a lighter-weight eieio. + */ +#define mb() __asm__ __volatile__ ("sync" : : : "memory") +#define rmb() __asm__ __volatile__ ("sync" : : : "memory") +#define wmb() __asm__ __volatile__ ("sync" : : : "memory") +#define read_barrier_depends() do { } while(0) + +#define set_mb(var, value) do { var = value; mb(); } while (0) + +#ifdef CONFIG_SMP + +#ifdef __SUBARCH_HAS_LWSYNC +# define SMPWMB LWSYNC +#else +# define SMPWMB eieio +#endif + +#define smp_mb() mb() +#define smp_rmb() __asm__ __volatile__ (stringify_in_c(LWSYNC) : : :"memory") +#define smp_wmb() __asm__ __volatile__ (stringify_in_c(SMPWMB) : : :"memory") +#define smp_read_barrier_depends() read_barrier_depends() +#else +#define smp_mb() barrier() +#define smp_rmb() barrier() +#define smp_wmb() barrier() +#define smp_read_barrier_depends() do { } while(0) +#endif /* CONFIG_SMP */ + +/* + * This is a barrier which prevents following instructions from being + * started until the value of the argument x is known. For example, if + * x is a variable loaded from memory, this prevents following + * instructions from being executed until the load has been performed. + */ +#define data_barrier(x) \ + asm volatile("twi 0,%0,0; isync" : : "r" (x) : "memory"); + +#endif /* _ASM_POWERPC_BARRIER_H */ |