lib/dma-direct.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * DMA operations that map physical memory directly without using an IOMMU or
   4  * flushing caches.
   5  */
   6 #include <linux/export.h>
   7 #include <linux/mm.h>
   8 #include <linux/dma-direct.h>
   9 #include <linux/scatterlist.h>
  10 #include <linux/dma-contiguous.h>
  11 #include <linux/pfn.h>
  12
  13 #define DIRECT_MAPPING_ERROR            0
  14
  15 /*
  16  * Most architectures use ZONE_DMA for the first 16 Megabytes, but
  17  * some use it for entirely different regions:
  18  */
  19 #ifndef ARCH_ZONE_DMA_BITS
  20 #define ARCH_ZONE_DMA_BITS 24
  21 #endif
  22
  23 static bool
  24 check_addr(struct device *dev, dma_addr_t dma_addr, size_t size,
  25                 const char *caller)
  26 {
  27         if (unlikely(dev && !dma_capable(dev, dma_addr, size))) {
  28                 if (*dev->dma_mask >= DMA_BIT_MASK(32)) {
  29                         dev_err(dev,
  30                                 "%s: overflow %pad+%zu of device mask %llx\n",
  31                                 caller, &dma_addr, size, *dev->dma_mask);
  32                 }
  33                 return false;
  34         }
  35         return true;
  36 }
  37
  38 static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
  39 {
  40         return phys_to_dma(dev, phys) + size - 1 <= dev->coherent_dma_mask;
  41 }
  42
  43 void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
  44                 gfp_t gfp, unsigned long attrs)
  45 {
  46         unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
  47         int page_order = get_order(size);
  48         struct page *page = NULL;
  49
  50         /* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
  51         if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
  52                 gfp |= GFP_DMA;
  53         if (dev->coherent_dma_mask <= DMA_BIT_MASK(32) && !(gfp & GFP_DMA))
  54                 gfp |= GFP_DMA32;
  55
  56 again:
  57         /* CMA can be used only in the context which permits sleeping */
  58         if (gfpflags_allow_blocking(gfp)) {
  59                 page = dma_alloc_from_contiguous(dev, count, page_order, gfp);
  60                 if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
  61                         dma_release_from_contiguous(dev, page, count);
  62                         page = NULL;
  63                 }
  64         }
  65         if (!page)
  66                 page = alloc_pages_node(dev_to_node(dev), gfp, page_order);
  67
  68         if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
  69                 __free_pages(page, page_order);
  70                 page = NULL;
  71
  72                 if (dev->coherent_dma_mask < DMA_BIT_MASK(32) &&
  73                     !(gfp & GFP_DMA)) {
  74                         gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
  75                         goto again;
  76                 }
  77         }
  78
  79         if (!page)
  80                 return NULL;
  81
  82         *dma_handle = phys_to_dma(dev, page_to_phys(page));
  83         memset(page_address(page), 0, size);
  84         return page_address(page);
  85 }
  86
  87 /*
  88  * NOTE: this function must never look at the dma_addr argument, because we want
  89  * to be able to use it as a helper for iommu implementations as well.
  90  */
  91 void dma_direct_free(struct device *dev, size_t size, void *cpu_addr,
  92                 dma_addr_t dma_addr, unsigned long attrs)
  93 {
  94         unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
  95
  96         if (!dma_release_from_contiguous(dev, virt_to_page(cpu_addr), count))
  97                 free_pages((unsigned long)cpu_addr, get_order(size));
  98 }
  99
 100 static dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
 101                 unsigned long offset, size_t size, enum dma_data_direction dir,
 102                 unsigned long attrs)
 103 {
 104         dma_addr_t dma_addr = phys_to_dma(dev, page_to_phys(page)) + offset;
 105
 106         if (!check_addr(dev, dma_addr, size, __func__))
 107                 return DIRECT_MAPPING_ERROR;
 108         return dma_addr;
 109 }
 110
 111 static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl,
 112                 int nents, enum dma_data_direction dir, unsigned long attrs)
 113 {
 114         int i;
 115         struct scatterlist *sg;
 116
 117         for_each_sg(sgl, sg, nents, i) {
 118                 BUG_ON(!sg_page(sg));
 119
 120                 sg_dma_address(sg) = phys_to_dma(dev, sg_phys(sg));
 121                 if (!check_addr(dev, sg_dma_address(sg), sg->length, __func__))
 122                         return 0;
 123                 sg_dma_len(sg) = sg->length;
 124         }
 125
 126         return nents;
 127 }
 128
 129 int dma_direct_supported(struct device *dev, u64 mask)
 130 {
 131 #ifdef CONFIG_ZONE_DMA
 132         if (mask < DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
 133                 return 0;
 134 #else
 135         /*
 136          * Because 32-bit DMA masks are so common we expect every architecture
 137          * to be able to satisfy them - either by not supporting more physical
 138          * memory, or by providing a ZONE_DMA32.  If neither is the case, the
 139          * architecture needs to use an IOMMU instead of the direct mapping.
 140          */
 141         if (mask < DMA_BIT_MASK(32))
 142                 return 0;
 143 #endif
 144         return 1;
 145 }
 146
 147 static int dma_direct_mapping_error(struct device *dev, dma_addr_t dma_addr)
 148 {
 149         return dma_addr == DIRECT_MAPPING_ERROR;
 150 }
 151
 152 const struct dma_map_ops dma_direct_ops = {
 153         .alloc                  = dma_direct_alloc,
 154         .free                   = dma_direct_free,
 155         .map_page               = dma_direct_map_page,
 156         .map_sg                 = dma_direct_map_sg,
 157         .dma_supported          = dma_direct_supported,
 158         .mapping_error          = dma_direct_mapping_error,
 159         .is_phys                = 1,
 160 };
 161 EXPORT_SYMBOL(dma_direct_ops);