include/linux/pmem.h

   1 /*
   2  * Copyright(c) 2015 Intel Corporation. All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of version 2 of the GNU General Public License as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  */
  13 #ifndef __PMEM_H__
  14 #define __PMEM_H__
  15
  16 #include <linux/io.h>
  17
  18 #ifdef CONFIG_ARCH_HAS_PMEM_API
  19 #include <asm/cacheflush.h>
  20 #else
  21 static inline void arch_wmb_pmem(void)
  22 {
  23         BUG();
  24 }
  25
  26 static inline bool __arch_has_wmb_pmem(void)
  27 {
  28         return false;
  29 }
  30
  31 static inline void __pmem *arch_memremap_pmem(resource_size_t offset,
  32                 unsigned long size)
  33 {
  34         return NULL;
  35 }
  36
  37 static inline void arch_memcpy_to_pmem(void __pmem *dst, const void *src,
  38                 size_t n)
  39 {
  40         BUG();
  41 }
  42 #endif
  43
  44 /*
  45  * Architectures that define ARCH_HAS_PMEM_API must provide
  46  * implementations for arch_memremap_pmem(), arch_memcpy_to_pmem(),
  47  * arch_wmb_pmem(), and __arch_has_wmb_pmem().
  48  */
  49
  50 static inline void memcpy_from_pmem(void *dst, void __pmem const *src, size_t size)
  51 {
  52         memcpy(dst, (void __force const *) src, size);
  53 }
  54
  55 static inline void memunmap_pmem(void __pmem *addr)
  56 {
  57         iounmap((void __force __iomem *) addr);
  58 }
  59
  60 /**
  61  * arch_has_wmb_pmem - true if wmb_pmem() ensures durability
  62  *
  63  * For a given cpu implementation within an architecture it is possible
  64  * that wmb_pmem() resolves to a nop.  In the case this returns
  65  * false, pmem api users are unable to ensure durability and may want to
  66  * fall back to a different data consistency model, or otherwise notify
  67  * the user.
  68  */
  69 static inline bool arch_has_wmb_pmem(void)
  70 {
  71         if (IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API))
  72                 return __arch_has_wmb_pmem();
  73         return false;
  74 }
  75
  76 static inline bool arch_has_pmem_api(void)
  77 {
  78         return IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API) && arch_has_wmb_pmem();
  79 }
  80
  81 /*
  82  * These defaults seek to offer decent performance and minimize the
  83  * window between i/o completion and writes being durable on media.
  84  * However, it is undefined / architecture specific whether
  85  * default_memremap_pmem + default_memcpy_to_pmem is sufficient for
  86  * making data durable relative to i/o completion.
  87  */
  88 static void default_memcpy_to_pmem(void __pmem *dst, const void *src,
  89                 size_t size)
  90 {
  91         memcpy((void __force *) dst, src, size);
  92 }
  93
  94 static void __pmem *default_memremap_pmem(resource_size_t offset,
  95                 unsigned long size)
  96 {
  97         return (void __pmem __force *)ioremap_wt(offset, size);
  98 }
  99
 100 /**
 101  * memremap_pmem - map physical persistent memory for pmem api
 102  * @offset: physical address of persistent memory
 103  * @size: size of the mapping
 104  *
 105  * Establish a mapping of the architecture specific memory type expected
 106  * by memcpy_to_pmem() and wmb_pmem().  For example, it may be
 107  * the case that an uncacheable or writethrough mapping is sufficient,
 108  * or a writeback mapping provided memcpy_to_pmem() and
 109  * wmb_pmem() arrange for the data to be written through the
 110  * cache to persistent media.
 111  */
 112 static inline void __pmem *memremap_pmem(resource_size_t offset,
 113                 unsigned long size)
 114 {
 115         if (arch_has_pmem_api())
 116                 return arch_memremap_pmem(offset, size);
 117         return default_memremap_pmem(offset, size);
 118 }
 119
 120 /**
 121  * memcpy_to_pmem - copy data to persistent memory
 122  * @dst: destination buffer for the copy
 123  * @src: source buffer for the copy
 124  * @n: length of the copy in bytes
 125  *
 126  * Perform a memory copy that results in the destination of the copy
 127  * being effectively evicted from, or never written to, the processor
 128  * cache hierarchy after the copy completes.  After memcpy_to_pmem()
 129  * data may still reside in cpu or platform buffers, so this operation
 130  * must be followed by a wmb_pmem().
 131  */
 132 static inline void memcpy_to_pmem(void __pmem *dst, const void *src, size_t n)
 133 {
 134         if (arch_has_pmem_api())
 135                 arch_memcpy_to_pmem(dst, src, n);
 136         else
 137                 default_memcpy_to_pmem(dst, src, n);
 138 }
 139
 140 /**
 141  * wmb_pmem - synchronize writes to persistent memory
 142  *
 143  * After a series of memcpy_to_pmem() operations this drains data from
 144  * cpu write buffers and any platform (memory controller) buffers to
 145  * ensure that written data is durable on persistent memory media.
 146  */
 147 static inline void wmb_pmem(void)
 148 {
 149         if (arch_has_pmem_api())
 150                 arch_wmb_pmem();
 151 }
 152 #endif /* __PMEM_H__ */