LXR linux/arch/powerpc/include/asm/barrier.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2/*
   3 * Copyright (C) 1999 Cort Dougan <cort@cs.nmt.edu>
   4 */
   5#ifndef _ASM_POWERPC_BARRIER_H
   6#define _ASM_POWERPC_BARRIER_H
   7
   8#include <asm/asm-const.h>
   9
  10#ifndef __ASSEMBLY__
  11#include <asm/ppc-opcode.h>
  12#endif
  13
  14/*
  15 * Memory barrier.
  16 * The sync instruction guarantees that all memory accesses initiated
  17 * by this processor have been performed (with respect to all other
  18 * mechanisms that access memory).  The eieio instruction is a barrier
  19 * providing an ordering (separately) for (a) cacheable stores and (b)
  20 * loads and stores to non-cacheable memory (e.g. I/O devices).
  21 *
  22 * mb() prevents loads and stores being reordered across this point.
  23 * rmb() prevents loads being reordered across this point.
  24 * wmb() prevents stores being reordered across this point.
  25 *
  26 * *mb() variants without smp_ prefix must order all types of memory
  27 * operations with one another. sync is the only instruction sufficient
  28 * to do this.
  29 *
  30 * For the smp_ barriers, ordering is for cacheable memory operations
  31 * only. We have to use the sync instruction for smp_mb(), since lwsync
  32 * doesn't order loads with respect to previous stores.  Lwsync can be
  33 * used for smp_rmb() and smp_wmb().
  34 *
  35 * However, on CPUs that don't support lwsync, lwsync actually maps to a
  36 * heavy-weight sync, so smp_wmb() can be a lighter-weight eieio.
  37 */
  38#define mb()   __asm__ __volatile__ ("sync" : : : "memory")
  39#define rmb()  __asm__ __volatile__ ("sync" : : : "memory")
  40#define wmb()  __asm__ __volatile__ ("sync" : : : "memory")
  41
  42/* The sub-arch has lwsync */
  43#if defined(CONFIG_PPC64) || defined(CONFIG_PPC_E500MC)
  44#    define SMPWMB      LWSYNC
  45#else
  46#    define SMPWMB      eieio
  47#endif
  48
  49/* clang defines this macro for a builtin, which will not work with runtime patching */
  50#undef __lwsync
  51#define __lwsync()      __asm__ __volatile__ (stringify_in_c(LWSYNC) : : :"memory")
  52#define dma_rmb()       __lwsync()
  53#define dma_wmb()       __asm__ __volatile__ (stringify_in_c(SMPWMB) : : :"memory")
  54
  55#define __smp_lwsync()  __lwsync()
  56
  57#define __smp_mb()      mb()
  58#define __smp_rmb()     __lwsync()
  59#define __smp_wmb()     __asm__ __volatile__ (stringify_in_c(SMPWMB) : : :"memory")
  60
  61/*
  62 * This is a barrier which prevents following instructions from being
  63 * started until the value of the argument x is known.  For example, if
  64 * x is a variable loaded from memory, this prevents following
  65 * instructions from being executed until the load has been performed.
  66 */
  67#define data_barrier(x) \
  68        asm volatile("twi 0,%0,0; isync" : : "r" (x) : "memory");
  69
  70#define __smp_store_release(p, v)                                               \
  71do {                                                                    \
  72        compiletime_assert_atomic_type(*p);                             \
  73        __smp_lwsync();                                                 \
  74        WRITE_ONCE(*p, v);                                              \
  75} while (0)
  76
  77#define __smp_load_acquire(p)                                           \
  78({                                                                      \
  79        typeof(*p) ___p1 = READ_ONCE(*p);                               \
  80        compiletime_assert_atomic_type(*p);                             \
  81        __smp_lwsync();                                                 \
  82        ___p1;                                                          \
  83})
  84
  85#ifdef CONFIG_PPC_BOOK3S_64
  86#define NOSPEC_BARRIER_SLOT   nop
  87#elif defined(CONFIG_PPC_FSL_BOOK3E)
  88#define NOSPEC_BARRIER_SLOT   nop; nop
  89#endif
  90
  91#ifdef CONFIG_PPC_BARRIER_NOSPEC
  92/*
  93 * Prevent execution of subsequent instructions until preceding branches have
  94 * been fully resolved and are no longer executing speculatively.
  95 */
  96#define barrier_nospec_asm NOSPEC_BARRIER_FIXUP_SECTION; NOSPEC_BARRIER_SLOT
  97
  98// This also acts as a compiler barrier due to the memory clobber.
  99#define barrier_nospec() asm (stringify_in_c(barrier_nospec_asm) ::: "memory")
 100
 101#else /* !CONFIG_PPC_BARRIER_NOSPEC */
 102#define barrier_nospec_asm
 103#define barrier_nospec()
 104#endif /* CONFIG_PPC_BARRIER_NOSPEC */
 105
 106/*
 107 * pmem_wmb() ensures that all stores for which the modification
 108 * are written to persistent storage by preceding dcbfps/dcbstps
 109 * instructions have updated persistent storage before any data
 110 * access or data transfer caused by subsequent instructions is
 111 * initiated.
 112 */
 113#define pmem_wmb() __asm__ __volatile__(PPC_PHWSYNC ::: "memory")
 114
 115#include <asm-generic/barrier.h>
 116
 117#endif /* _ASM_POWERPC_BARRIER_H */
 118