LXR linux/include/linux/prefetch.h

   1/* SPDX-License-Identifier: GPL-2.0 */
   2/*
   3 *  Generic cache management functions. Everything is arch-specific,  
   4 *  but this header exists to make sure the defines/functions can be
   5 *  used in a generic way.
   6 *
   7 *  2000-11-13  Arjan van de Ven   <arjan@fenrus.demon.nl>
   8 *
   9 */
  10
  11#ifndef _LINUX_PREFETCH_H
  12#define _LINUX_PREFETCH_H
  13
  14#include <linux/types.h>
  15#include <asm/processor.h>
  16#include <asm/cache.h>
  17
  18/*
  19        prefetch(x) attempts to pre-emptively get the memory pointed to
  20        by address "x" into the CPU L1 cache. 
  21        prefetch(x) should not cause any kind of exception, prefetch(0) is
  22        specifically ok.
  23
  24        prefetch() should be defined by the architecture, if not, the 
  25        #define below provides a no-op define.  
  26        
  27        There are 3 prefetch() macros:
  28        
  29        prefetch(x)     - prefetches the cacheline at "x" for read
  30        prefetchw(x)    - prefetches the cacheline at "x" for write
  31        spin_lock_prefetch(x) - prefetches the spinlock *x for taking
  32        
  33        there is also PREFETCH_STRIDE which is the architecure-preferred 
  34        "lookahead" size for prefetching streamed operations.
  35        
  36*/
  37
  38#ifndef ARCH_HAS_PREFETCH
  39#define prefetch(x) __builtin_prefetch(x)
  40#endif
  41
  42#ifndef ARCH_HAS_PREFETCHW
  43#define prefetchw(x) __builtin_prefetch(x,1)
  44#endif
  45
  46#ifndef ARCH_HAS_SPINLOCK_PREFETCH
  47#define spin_lock_prefetch(x) prefetchw(x)
  48#endif
  49
  50#ifndef PREFETCH_STRIDE
  51#define PREFETCH_STRIDE (4*L1_CACHE_BYTES)
  52#endif
  53
  54static inline void prefetch_range(void *addr, size_t len)
  55{
  56#ifdef ARCH_HAS_PREFETCH
  57        char *cp;
  58        char *end = addr + len;
  59
  60        for (cp = addr; cp < end; cp += PREFETCH_STRIDE)
  61                prefetch(cp);
  62#endif
  63}
  64
  65#endif
  66