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/*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
* Copyright (C) 2006 by Ralf Baechle (ralf@linux-mips.org)
*/
#ifndef __ASM_BARRIER_H
#define __ASM_BARRIER_H
/*
* read_barrier_depends - Flush all pending reads that subsequents reads
* depend on.
*
* No data-dependent reads from memory-like regions are ever reordered
* over this barrier. All reads preceding this primitive are guaranteed
* to access memory (but not necessarily other CPUs' caches) before any
* reads following this primitive that depend on the data return by
* any of the preceding reads. This primitive is much lighter weight than
* rmb() on most CPUs, and is never heavier weight than is
* rmb().
*
* These ordering constraints are respected by both the local CPU
* and the compiler.
*
* Ordering is not guaranteed by anything other than these primitives,
* not even by data dependencies. See the documentation for
* memory_barrier() for examples and URLs to more information.
*
* For example, the following code would force ordering (the initial
* value of "a" is zero, "b" is one, and "p" is "&a"):
*
* <programlisting>
* CPU 0 CPU 1
*
* b = 2;
* memory_barrier();
* p = &b; q = p;
* read_barrier_depends();
* d = *q;
* </programlisting>
*
* because the read of "*q" depends on the read of "p" and these
* two reads are separated by a read_barrier_depends(). However,
* the following code, with the same initial values for "a" and "b":
*
* <programlisting>
* CPU 0 CPU 1
*
* a = 2;
* memory_barrier();
* b = 3; y = b;
* read_barrier_depends();
* x = a;
* </programlisting>
*
* does not enforce ordering, since there is no data dependency between
* the read of "a" and the read of "b". Therefore, on some CPUs, such
* as Alpha, "y" could be set to 3 and "x" to 0. Use rmb()
* in cases like this where there are no data dependencies.
*/
#define read_barrier_depends() do { } while(0)
#define smp_read_barrier_depends() do { } while(0)
#ifdef CONFIG_CPU_HAS_SYNC
#define __sync() \
__asm__ __volatile__( \
".set push\n\t" \
".set noreorder\n\t" \
".set mips2\n\t" \
"sync\n\t" \
".set pop" \
: /* no output */ \
: /* no input */ \
: "memory")
#else
#define __sync() do { } while(0)
#endif
#define __fast_iob() \
__asm__ __volatile__( \
".set push\n\t" \
".set noreorder\n\t" \
"lw $0,%0\n\t" \
"nop\n\t" \
".set pop" \
: /* no output */ \
: "m" (*(int *)CKSEG1) \
: "memory")
#define fast_wmb() __sync()
#define fast_rmb() __sync()
#define fast_mb() __sync()
#define fast_iob() \
do { \
__sync(); \
__fast_iob(); \
} while (0)
#ifdef CONFIG_CPU_HAS_WB
#include <asm/wbflush.h>
#define wmb() fast_wmb()
#define rmb() fast_rmb()
#define mb() wbflush()
#define iob() wbflush()
#else /* !CONFIG_CPU_HAS_WB */
#define wmb() fast_wmb()
#define rmb() fast_rmb()
#define mb() fast_mb()
#define iob() fast_iob()
#endif /* !CONFIG_CPU_HAS_WB */
#if defined(CONFIG_WEAK_ORDERING) && defined(CONFIG_SMP)
#define __WEAK_ORDERING_MB " sync \n"
#else
#define __WEAK_ORDERING_MB " \n"
#endif
#define smp_mb() __asm__ __volatile__(__WEAK_ORDERING_MB : : :"memory")
#define smp_rmb() __asm__ __volatile__(__WEAK_ORDERING_MB : : :"memory")
#define smp_wmb() __asm__ __volatile__(__WEAK_ORDERING_MB : : :"memory")
#define set_mb(var, value) \
do { var = value; smp_mb(); } while (0)
#endif /* __ASM_BARRIER_H */
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