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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /kernel/dma/direct.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'kernel/dma/direct.c')
-rw-r--r--kernel/dma/direct.c655
1 files changed, 655 insertions, 0 deletions
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
new file mode 100644
index 0000000000..9596ae1aa0
--- /dev/null
+++ b/kernel/dma/direct.c
@@ -0,0 +1,655 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2018-2020 Christoph Hellwig.
+ *
+ * DMA operations that map physical memory directly without using an IOMMU.
+ */
+#include <linux/memblock.h> /* for max_pfn */
+#include <linux/export.h>
+#include <linux/mm.h>
+#include <linux/dma-map-ops.h>
+#include <linux/scatterlist.h>
+#include <linux/pfn.h>
+#include <linux/vmalloc.h>
+#include <linux/set_memory.h>
+#include <linux/slab.h>
+#include "direct.h"
+
+/*
+ * Most architectures use ZONE_DMA for the first 16 Megabytes, but some use
+ * it for entirely different regions. In that case the arch code needs to
+ * override the variable below for dma-direct to work properly.
+ */
+unsigned int zone_dma_bits __ro_after_init = 24;
+
+static inline dma_addr_t phys_to_dma_direct(struct device *dev,
+ phys_addr_t phys)
+{
+ if (force_dma_unencrypted(dev))
+ return phys_to_dma_unencrypted(dev, phys);
+ return phys_to_dma(dev, phys);
+}
+
+static inline struct page *dma_direct_to_page(struct device *dev,
+ dma_addr_t dma_addr)
+{
+ return pfn_to_page(PHYS_PFN(dma_to_phys(dev, dma_addr)));
+}
+
+u64 dma_direct_get_required_mask(struct device *dev)
+{
+ phys_addr_t phys = (phys_addr_t)(max_pfn - 1) << PAGE_SHIFT;
+ u64 max_dma = phys_to_dma_direct(dev, phys);
+
+ return (1ULL << (fls64(max_dma) - 1)) * 2 - 1;
+}
+
+static gfp_t dma_direct_optimal_gfp_mask(struct device *dev, u64 *phys_limit)
+{
+ u64 dma_limit = min_not_zero(
+ dev->coherent_dma_mask,
+ dev->bus_dma_limit);
+
+ /*
+ * Optimistically try the zone that the physical address mask falls
+ * into first. If that returns memory that isn't actually addressable
+ * we will fallback to the next lower zone and try again.
+ *
+ * Note that GFP_DMA32 and GFP_DMA are no ops without the corresponding
+ * zones.
+ */
+ *phys_limit = dma_to_phys(dev, dma_limit);
+ if (*phys_limit <= DMA_BIT_MASK(zone_dma_bits))
+ return GFP_DMA;
+ if (*phys_limit <= DMA_BIT_MASK(32))
+ return GFP_DMA32;
+ return 0;
+}
+
+bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
+{
+ dma_addr_t dma_addr = phys_to_dma_direct(dev, phys);
+
+ if (dma_addr == DMA_MAPPING_ERROR)
+ return false;
+ return dma_addr + size - 1 <=
+ min_not_zero(dev->coherent_dma_mask, dev->bus_dma_limit);
+}
+
+static int dma_set_decrypted(struct device *dev, void *vaddr, size_t size)
+{
+ if (!force_dma_unencrypted(dev))
+ return 0;
+ return set_memory_decrypted((unsigned long)vaddr, PFN_UP(size));
+}
+
+static int dma_set_encrypted(struct device *dev, void *vaddr, size_t size)
+{
+ int ret;
+
+ if (!force_dma_unencrypted(dev))
+ return 0;
+ ret = set_memory_encrypted((unsigned long)vaddr, PFN_UP(size));
+ if (ret)
+ pr_warn_ratelimited("leaking DMA memory that can't be re-encrypted\n");
+ return ret;
+}
+
+static void __dma_direct_free_pages(struct device *dev, struct page *page,
+ size_t size)
+{
+ if (swiotlb_free(dev, page, size))
+ return;
+ dma_free_contiguous(dev, page, size);
+}
+
+static struct page *dma_direct_alloc_swiotlb(struct device *dev, size_t size)
+{
+ struct page *page = swiotlb_alloc(dev, size);
+
+ if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
+ swiotlb_free(dev, page, size);
+ return NULL;
+ }
+
+ return page;
+}
+
+static struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
+ gfp_t gfp, bool allow_highmem)
+{
+ int node = dev_to_node(dev);
+ struct page *page = NULL;
+ u64 phys_limit;
+
+ WARN_ON_ONCE(!PAGE_ALIGNED(size));
+
+ if (is_swiotlb_for_alloc(dev))
+ return dma_direct_alloc_swiotlb(dev, size);
+
+ gfp |= dma_direct_optimal_gfp_mask(dev, &phys_limit);
+ page = dma_alloc_contiguous(dev, size, gfp);
+ if (page) {
+ if (!dma_coherent_ok(dev, page_to_phys(page), size) ||
+ (!allow_highmem && PageHighMem(page))) {
+ dma_free_contiguous(dev, page, size);
+ page = NULL;
+ }
+ }
+again:
+ if (!page)
+ page = alloc_pages_node(node, gfp, get_order(size));
+ if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
+ dma_free_contiguous(dev, page, size);
+ page = NULL;
+
+ if (IS_ENABLED(CONFIG_ZONE_DMA32) &&
+ phys_limit < DMA_BIT_MASK(64) &&
+ !(gfp & (GFP_DMA32 | GFP_DMA))) {
+ gfp |= GFP_DMA32;
+ goto again;
+ }
+
+ if (IS_ENABLED(CONFIG_ZONE_DMA) && !(gfp & GFP_DMA)) {
+ gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
+ goto again;
+ }
+ }
+
+ return page;
+}
+
+/*
+ * Check if a potentially blocking operations needs to dip into the atomic
+ * pools for the given device/gfp.
+ */
+static bool dma_direct_use_pool(struct device *dev, gfp_t gfp)
+{
+ return !gfpflags_allow_blocking(gfp) && !is_swiotlb_for_alloc(dev);
+}
+
+static void *dma_direct_alloc_from_pool(struct device *dev, size_t size,
+ dma_addr_t *dma_handle, gfp_t gfp)
+{
+ struct page *page;
+ u64 phys_limit;
+ void *ret;
+
+ if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_DMA_COHERENT_POOL)))
+ return NULL;
+
+ gfp |= dma_direct_optimal_gfp_mask(dev, &phys_limit);
+ page = dma_alloc_from_pool(dev, size, &ret, gfp, dma_coherent_ok);
+ if (!page)
+ return NULL;
+ *dma_handle = phys_to_dma_direct(dev, page_to_phys(page));
+ return ret;
+}
+
+static void *dma_direct_alloc_no_mapping(struct device *dev, size_t size,
+ dma_addr_t *dma_handle, gfp_t gfp)
+{
+ struct page *page;
+
+ page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO, true);
+ if (!page)
+ return NULL;
+
+ /* remove any dirty cache lines on the kernel alias */
+ if (!PageHighMem(page))
+ arch_dma_prep_coherent(page, size);
+
+ /* return the page pointer as the opaque cookie */
+ *dma_handle = phys_to_dma_direct(dev, page_to_phys(page));
+ return page;
+}
+
+void *dma_direct_alloc(struct device *dev, size_t size,
+ dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
+{
+ bool remap = false, set_uncached = false;
+ struct page *page;
+ void *ret;
+
+ size = PAGE_ALIGN(size);
+ if (attrs & DMA_ATTR_NO_WARN)
+ gfp |= __GFP_NOWARN;
+
+ if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) &&
+ !force_dma_unencrypted(dev) && !is_swiotlb_for_alloc(dev))
+ return dma_direct_alloc_no_mapping(dev, size, dma_handle, gfp);
+
+ if (!dev_is_dma_coherent(dev)) {
+ /*
+ * Fallback to the arch handler if it exists. This should
+ * eventually go away.
+ */
+ if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) &&
+ !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
+ !IS_ENABLED(CONFIG_DMA_GLOBAL_POOL) &&
+ !is_swiotlb_for_alloc(dev))
+ return arch_dma_alloc(dev, size, dma_handle, gfp,
+ attrs);
+
+ /*
+ * If there is a global pool, always allocate from it for
+ * non-coherent devices.
+ */
+ if (IS_ENABLED(CONFIG_DMA_GLOBAL_POOL))
+ return dma_alloc_from_global_coherent(dev, size,
+ dma_handle);
+
+ /*
+ * Otherwise remap if the architecture is asking for it. But
+ * given that remapping memory is a blocking operation we'll
+ * instead have to dip into the atomic pools.
+ */
+ remap = IS_ENABLED(CONFIG_DMA_DIRECT_REMAP);
+ if (remap) {
+ if (dma_direct_use_pool(dev, gfp))
+ return dma_direct_alloc_from_pool(dev, size,
+ dma_handle, gfp);
+ } else {
+ if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED))
+ return NULL;
+ set_uncached = true;
+ }
+ }
+
+ /*
+ * Decrypting memory may block, so allocate the memory from the atomic
+ * pools if we can't block.
+ */
+ if (force_dma_unencrypted(dev) && dma_direct_use_pool(dev, gfp))
+ return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
+
+ /* we always manually zero the memory once we are done */
+ page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO, true);
+ if (!page)
+ return NULL;
+
+ /*
+ * dma_alloc_contiguous can return highmem pages depending on a
+ * combination the cma= arguments and per-arch setup. These need to be
+ * remapped to return a kernel virtual address.
+ */
+ if (PageHighMem(page)) {
+ remap = true;
+ set_uncached = false;
+ }
+
+ if (remap) {
+ pgprot_t prot = dma_pgprot(dev, PAGE_KERNEL, attrs);
+
+ if (force_dma_unencrypted(dev))
+ prot = pgprot_decrypted(prot);
+
+ /* remove any dirty cache lines on the kernel alias */
+ arch_dma_prep_coherent(page, size);
+
+ /* create a coherent mapping */
+ ret = dma_common_contiguous_remap(page, size, prot,
+ __builtin_return_address(0));
+ if (!ret)
+ goto out_free_pages;
+ } else {
+ ret = page_address(page);
+ if (dma_set_decrypted(dev, ret, size))
+ goto out_free_pages;
+ }
+
+ memset(ret, 0, size);
+
+ if (set_uncached) {
+ arch_dma_prep_coherent(page, size);
+ ret = arch_dma_set_uncached(ret, size);
+ if (IS_ERR(ret))
+ goto out_encrypt_pages;
+ }
+
+ *dma_handle = phys_to_dma_direct(dev, page_to_phys(page));
+ return ret;
+
+out_encrypt_pages:
+ if (dma_set_encrypted(dev, page_address(page), size))
+ return NULL;
+out_free_pages:
+ __dma_direct_free_pages(dev, page, size);
+ return NULL;
+}
+
+void dma_direct_free(struct device *dev, size_t size,
+ void *cpu_addr, dma_addr_t dma_addr, unsigned long attrs)
+{
+ unsigned int page_order = get_order(size);
+
+ if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) &&
+ !force_dma_unencrypted(dev) && !is_swiotlb_for_alloc(dev)) {
+ /* cpu_addr is a struct page cookie, not a kernel address */
+ dma_free_contiguous(dev, cpu_addr, size);
+ return;
+ }
+
+ if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) &&
+ !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
+ !IS_ENABLED(CONFIG_DMA_GLOBAL_POOL) &&
+ !dev_is_dma_coherent(dev) &&
+ !is_swiotlb_for_alloc(dev)) {
+ arch_dma_free(dev, size, cpu_addr, dma_addr, attrs);
+ return;
+ }
+
+ if (IS_ENABLED(CONFIG_DMA_GLOBAL_POOL) &&
+ !dev_is_dma_coherent(dev)) {
+ if (!dma_release_from_global_coherent(page_order, cpu_addr))
+ WARN_ON_ONCE(1);
+ return;
+ }
+
+ /* If cpu_addr is not from an atomic pool, dma_free_from_pool() fails */
+ if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) &&
+ dma_free_from_pool(dev, cpu_addr, PAGE_ALIGN(size)))
+ return;
+
+ if (is_vmalloc_addr(cpu_addr)) {
+ vunmap(cpu_addr);
+ } else {
+ if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_CLEAR_UNCACHED))
+ arch_dma_clear_uncached(cpu_addr, size);
+ if (dma_set_encrypted(dev, cpu_addr, size))
+ return;
+ }
+
+ __dma_direct_free_pages(dev, dma_direct_to_page(dev, dma_addr), size);
+}
+
+struct page *dma_direct_alloc_pages(struct device *dev, size_t size,
+ dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp)
+{
+ struct page *page;
+ void *ret;
+
+ if (force_dma_unencrypted(dev) && dma_direct_use_pool(dev, gfp))
+ return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
+
+ page = __dma_direct_alloc_pages(dev, size, gfp, false);
+ if (!page)
+ return NULL;
+
+ ret = page_address(page);
+ if (dma_set_decrypted(dev, ret, size))
+ goto out_free_pages;
+ memset(ret, 0, size);
+ *dma_handle = phys_to_dma_direct(dev, page_to_phys(page));
+ return page;
+out_free_pages:
+ __dma_direct_free_pages(dev, page, size);
+ return NULL;
+}
+
+void dma_direct_free_pages(struct device *dev, size_t size,
+ struct page *page, dma_addr_t dma_addr,
+ enum dma_data_direction dir)
+{
+ void *vaddr = page_address(page);
+
+ /* If cpu_addr is not from an atomic pool, dma_free_from_pool() fails */
+ if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) &&
+ dma_free_from_pool(dev, vaddr, size))
+ return;
+
+ if (dma_set_encrypted(dev, vaddr, size))
+ return;
+ __dma_direct_free_pages(dev, page, size);
+}
+
+#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
+ defined(CONFIG_SWIOTLB)
+void dma_direct_sync_sg_for_device(struct device *dev,
+ struct scatterlist *sgl, int nents, enum dma_data_direction dir)
+{
+ struct scatterlist *sg;
+ int i;
+
+ for_each_sg(sgl, sg, nents, i) {
+ phys_addr_t paddr = dma_to_phys(dev, sg_dma_address(sg));
+
+ if (unlikely(is_swiotlb_buffer(dev, paddr)))
+ swiotlb_sync_single_for_device(dev, paddr, sg->length,
+ dir);
+
+ if (!dev_is_dma_coherent(dev))
+ arch_sync_dma_for_device(paddr, sg->length,
+ dir);
+ }
+}
+#endif
+
+#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
+ defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL) || \
+ defined(CONFIG_SWIOTLB)
+void dma_direct_sync_sg_for_cpu(struct device *dev,
+ struct scatterlist *sgl, int nents, enum dma_data_direction dir)
+{
+ struct scatterlist *sg;
+ int i;
+
+ for_each_sg(sgl, sg, nents, i) {
+ phys_addr_t paddr = dma_to_phys(dev, sg_dma_address(sg));
+
+ if (!dev_is_dma_coherent(dev))
+ arch_sync_dma_for_cpu(paddr, sg->length, dir);
+
+ if (unlikely(is_swiotlb_buffer(dev, paddr)))
+ swiotlb_sync_single_for_cpu(dev, paddr, sg->length,
+ dir);
+
+ if (dir == DMA_FROM_DEVICE)
+ arch_dma_mark_clean(paddr, sg->length);
+ }
+
+ if (!dev_is_dma_coherent(dev))
+ arch_sync_dma_for_cpu_all();
+}
+
+/*
+ * Unmaps segments, except for ones marked as pci_p2pdma which do not
+ * require any further action as they contain a bus address.
+ */
+void dma_direct_unmap_sg(struct device *dev, struct scatterlist *sgl,
+ int nents, enum dma_data_direction dir, unsigned long attrs)
+{
+ struct scatterlist *sg;
+ int i;
+
+ for_each_sg(sgl, sg, nents, i) {
+ if (sg_dma_is_bus_address(sg))
+ sg_dma_unmark_bus_address(sg);
+ else
+ dma_direct_unmap_page(dev, sg->dma_address,
+ sg_dma_len(sg), dir, attrs);
+ }
+}
+#endif
+
+int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
+ enum dma_data_direction dir, unsigned long attrs)
+{
+ struct pci_p2pdma_map_state p2pdma_state = {};
+ enum pci_p2pdma_map_type map;
+ struct scatterlist *sg;
+ int i, ret;
+
+ for_each_sg(sgl, sg, nents, i) {
+ if (is_pci_p2pdma_page(sg_page(sg))) {
+ map = pci_p2pdma_map_segment(&p2pdma_state, dev, sg);
+ switch (map) {
+ case PCI_P2PDMA_MAP_BUS_ADDR:
+ continue;
+ case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE:
+ /*
+ * Any P2P mapping that traverses the PCI
+ * host bridge must be mapped with CPU physical
+ * address and not PCI bus addresses. This is
+ * done with dma_direct_map_page() below.
+ */
+ break;
+ default:
+ ret = -EREMOTEIO;
+ goto out_unmap;
+ }
+ }
+
+ sg->dma_address = dma_direct_map_page(dev, sg_page(sg),
+ sg->offset, sg->length, dir, attrs);
+ if (sg->dma_address == DMA_MAPPING_ERROR) {
+ ret = -EIO;
+ goto out_unmap;
+ }
+ sg_dma_len(sg) = sg->length;
+ }
+
+ return nents;
+
+out_unmap:
+ dma_direct_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
+ return ret;
+}
+
+dma_addr_t dma_direct_map_resource(struct device *dev, phys_addr_t paddr,
+ size_t size, enum dma_data_direction dir, unsigned long attrs)
+{
+ dma_addr_t dma_addr = paddr;
+
+ if (unlikely(!dma_capable(dev, dma_addr, size, false))) {
+ dev_err_once(dev,
+ "DMA addr %pad+%zu overflow (mask %llx, bus limit %llx).\n",
+ &dma_addr, size, *dev->dma_mask, dev->bus_dma_limit);
+ WARN_ON_ONCE(1);
+ return DMA_MAPPING_ERROR;
+ }
+
+ return dma_addr;
+}
+
+int dma_direct_get_sgtable(struct device *dev, struct sg_table *sgt,
+ void *cpu_addr, dma_addr_t dma_addr, size_t size,
+ unsigned long attrs)
+{
+ struct page *page = dma_direct_to_page(dev, dma_addr);
+ int ret;
+
+ ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
+ if (!ret)
+ sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
+ return ret;
+}
+
+bool dma_direct_can_mmap(struct device *dev)
+{
+ return dev_is_dma_coherent(dev) ||
+ IS_ENABLED(CONFIG_DMA_NONCOHERENT_MMAP);
+}
+
+int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma,
+ void *cpu_addr, dma_addr_t dma_addr, size_t size,
+ unsigned long attrs)
+{
+ unsigned long user_count = vma_pages(vma);
+ unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+ unsigned long pfn = PHYS_PFN(dma_to_phys(dev, dma_addr));
+ int ret = -ENXIO;
+
+ vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs);
+ if (force_dma_unencrypted(dev))
+ vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
+
+ if (dma_mmap_from_dev_coherent(dev, vma, cpu_addr, size, &ret))
+ return ret;
+ if (dma_mmap_from_global_coherent(vma, cpu_addr, size, &ret))
+ return ret;
+
+ if (vma->vm_pgoff >= count || user_count > count - vma->vm_pgoff)
+ return -ENXIO;
+ return remap_pfn_range(vma, vma->vm_start, pfn + vma->vm_pgoff,
+ user_count << PAGE_SHIFT, vma->vm_page_prot);
+}
+
+int dma_direct_supported(struct device *dev, u64 mask)
+{
+ u64 min_mask = (max_pfn - 1) << PAGE_SHIFT;
+
+ /*
+ * Because 32-bit DMA masks are so common we expect every architecture
+ * to be able to satisfy them - either by not supporting more physical
+ * memory, or by providing a ZONE_DMA32. If neither is the case, the
+ * architecture needs to use an IOMMU instead of the direct mapping.
+ */
+ if (mask >= DMA_BIT_MASK(32))
+ return 1;
+
+ /*
+ * This check needs to be against the actual bit mask value, so use
+ * phys_to_dma_unencrypted() here so that the SME encryption mask isn't
+ * part of the check.
+ */
+ if (IS_ENABLED(CONFIG_ZONE_DMA))
+ min_mask = min_t(u64, min_mask, DMA_BIT_MASK(zone_dma_bits));
+ return mask >= phys_to_dma_unencrypted(dev, min_mask);
+}
+
+size_t dma_direct_max_mapping_size(struct device *dev)
+{
+ /* If SWIOTLB is active, use its maximum mapping size */
+ if (is_swiotlb_active(dev) &&
+ (dma_addressing_limited(dev) || is_swiotlb_force_bounce(dev)))
+ return swiotlb_max_mapping_size(dev);
+ return SIZE_MAX;
+}
+
+bool dma_direct_need_sync(struct device *dev, dma_addr_t dma_addr)
+{
+ return !dev_is_dma_coherent(dev) ||
+ is_swiotlb_buffer(dev, dma_to_phys(dev, dma_addr));
+}
+
+/**
+ * dma_direct_set_offset - Assign scalar offset for a single DMA range.
+ * @dev: device pointer; needed to "own" the alloced memory.
+ * @cpu_start: beginning of memory region covered by this offset.
+ * @dma_start: beginning of DMA/PCI region covered by this offset.
+ * @size: size of the region.
+ *
+ * This is for the simple case of a uniform offset which cannot
+ * be discovered by "dma-ranges".
+ *
+ * It returns -ENOMEM if out of memory, -EINVAL if a map
+ * already exists, 0 otherwise.
+ *
+ * Note: any call to this from a driver is a bug. The mapping needs
+ * to be described by the device tree or other firmware interfaces.
+ */
+int dma_direct_set_offset(struct device *dev, phys_addr_t cpu_start,
+ dma_addr_t dma_start, u64 size)
+{
+ struct bus_dma_region *map;
+ u64 offset = (u64)cpu_start - (u64)dma_start;
+
+ if (dev->dma_range_map) {
+ dev_err(dev, "attempt to add DMA range to existing map\n");
+ return -EINVAL;
+ }
+
+ if (!offset)
+ return 0;
+
+ map = kcalloc(2, sizeof(*map), GFP_KERNEL);
+ if (!map)
+ return -ENOMEM;
+ map[0].cpu_start = cpu_start;
+ map[0].dma_start = dma_start;
+ map[0].offset = offset;
+ map[0].size = size;
+ dev->dma_range_map = map;
+ return 0;
+}