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 void dma_direct_free(struct device *dev, size_t size, void *cpu_addr,
  88                 dma_addr_t dma_addr, unsigned long attrs)
  89 {
  90         unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
  91
  92         if (!dma_release_from_contiguous(dev, virt_to_page(cpu_addr), count))
  93                 free_pages((unsigned long)cpu_addr, get_order(size));
  94 }
  95
  96 static dma_addr_t dma_direct_map_page(struct device *dev, struct page *page,
  97                 unsigned long offset, size_t size, enum dma_data_direction dir,
  98                 unsigned long attrs)
  99 {
 100         dma_addr_t dma_addr = phys_to_dma(dev, page_to_phys(page)) + offset;
 101
 102         if (!check_addr(dev, dma_addr, size, __func__))
 103                 return DIRECT_MAPPING_ERROR;
 104         return dma_addr;
 105 }
 106
 107 static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl,
 108                 int nents, enum dma_data_direction dir, unsigned long attrs)
 109 {
 110         int i;
 111         struct scatterlist *sg;
 112
 113         for_each_sg(sgl, sg, nents, i) {
 114                 BUG_ON(!sg_page(sg));
 115
 116                 sg_dma_address(sg) = phys_to_dma(dev, sg_phys(sg));
 117                 if (!check_addr(dev, sg_dma_address(sg), sg->length, __func__))
 118                         return 0;
 119                 sg_dma_len(sg) = sg->length;
 120         }
 121
 122         return nents;
 123 }
 124
 125 int dma_direct_supported(struct device *dev, u64 mask)
 126 {
 127 #ifdef CONFIG_ZONE_DMA
 128         if (mask < DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
 129                 return 0;
 130 #else
 131         /*
 132          * Because 32-bit DMA masks are so common we expect every architecture
 133          * to be able to satisfy them - either by not supporting more physical
 134          * memory, or by providing a ZONE_DMA32.  If neither is the case, the
 135          * architecture needs to use an IOMMU instead of the direct mapping.
 136          */
 137         if (mask < DMA_BIT_MASK(32))
 138                 return 0;
 139 #endif
 140         return 1;
 141 }
 142
 143 static int dma_direct_mapping_error(struct device *dev, dma_addr_t dma_addr)
 144 {
 145         return dma_addr == DIRECT_MAPPING_ERROR;
 146 }
 147
 148 const struct dma_map_ops dma_direct_ops = {
 149         .alloc                  = dma_direct_alloc,
 150         .free                   = dma_direct_free,
 151         .map_page               = dma_direct_map_page,
 152         .map_sg                 = dma_direct_map_sg,
 153         .dma_supported          = dma_direct_supported,
 154         .mapping_error          = dma_direct_mapping_error,
 155 };
 156 EXPORT_SYMBOL(dma_direct_ops);