[v4,2/4] WIP: add a dma_alloc_contiguous API

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 73249732afd3..2e72fe1b9c3b 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -564,23 +564,12 @@  static struct page **__iommu_dma_alloc_pages(struct device *dev,
 	return pages;
 }
 
-/**
- * iommu_dma_alloc_remap - Allocate and map a buffer contiguous in IOVA space
- * @dev: Device to allocate memory for. Must be a real device
- *	 attached to an iommu_dma_domain
- * @size: Size of buffer in bytes
- * @dma_handle: Out argument for allocated DMA handle
- * @gfp: Allocation flags
- * @prot: pgprot_t to use for the remapped mapping
- * @attrs: DMA attributes for this allocation
- *
- * If @size is less than PAGE_SIZE, then a full CPU page will be allocated,
+/*
+ * If size is less than PAGE_SIZE, then a full CPU page will be allocated,
  * but an IOMMU which supports smaller pages might not map the whole thing.
- *
- * Return: Mapped virtual address, or NULL on failure.
  */
-static void *iommu_dma_alloc_remap(struct device *dev, size_t size,
-		dma_addr_t *dma_handle, gfp_t gfp, pgprot_t prot,
+static struct page **__iommu_dma_alloc_noncontiguous(struct device *dev,
+		size_t size, dma_addr_t *dma_handle, gfp_t gfp, pgprot_t prot,
 		unsigned long attrs)
 {
 	struct iommu_domain *domain = iommu_get_dma_domain(dev);
@@ -592,7 +581,6 @@  static void *iommu_dma_alloc_remap(struct device *dev, size_t size,
 	struct page **pages;
 	struct sg_table sgt;
 	dma_addr_t iova;
-	void *vaddr;
 
 	*dma_handle = DMA_MAPPING_ERROR;
 
@@ -635,17 +623,10 @@  static void *iommu_dma_alloc_remap(struct device *dev, size_t size,
 			< size)
 		goto out_free_sg;
 
-	vaddr = dma_common_pages_remap(pages, size, prot,
-			__builtin_return_address(0));
-	if (!vaddr)
-		goto out_unmap;
-
 	*dma_handle = iova;
 	sg_free_table(&sgt);
-	return vaddr;
+	return pages;
 
-out_unmap:
-	__iommu_dma_unmap(dev, iova, size);
 out_free_sg:
 	sg_free_table(&sgt);
 out_free_iova:
@@ -655,20 +636,45 @@  static void *iommu_dma_alloc_remap(struct device *dev, size_t size,
 	return NULL;
 }
 
-/**
- * __iommu_dma_mmap - Map a buffer into provided user VMA
- * @pages: Array representing buffer from __iommu_dma_alloc()
- * @size: Size of buffer in bytes
- * @vma: VMA describing requested userspace mapping
- *
- * Maps the pages of the buffer in @pages into @vma. The caller is responsible
- * for verifying the correct size and protection of @vma beforehand.
- */
-static int __iommu_dma_mmap(struct page **pages, size_t size,
-		struct vm_area_struct *vma)
+static void *iommu_dma_alloc_remap(struct device *dev, size_t size,
+		dma_addr_t *dma_handle, gfp_t gfp, pgprot_t prot,
+		unsigned long attrs)
 {
-	return vm_map_pages(vma, pages, PAGE_ALIGN(size) >> PAGE_SHIFT);
+	struct page **pages;
+	void *vaddr;
+
+	pages = __iommu_dma_alloc_noncontiguous(dev, size, dma_handle, gfp,
+						prot, attrs);
+	if (!pages)
+		return NULL;
+	vaddr = dma_common_pages_remap(pages, size, prot,
+			__builtin_return_address(0));
+	if (!vaddr)
+		goto out_unmap;
+	return vaddr;
+
+out_unmap:
+	__iommu_dma_unmap(dev, *dma_handle, size);
+	__iommu_dma_free_pages(pages, PAGE_ALIGN(size) >> PAGE_SHIFT);
+	return NULL;
+}
+
+#ifdef CONFIG_DMA_REMAP
+static struct page **iommu_dma_alloc_noncontiguous(struct device *dev,
+		size_t size, dma_addr_t *dma_handle, gfp_t gfp,
+		unsigned long attrs)
+{
+	return __iommu_dma_alloc_noncontiguous(dev, size, dma_handle, gfp,
+					       PAGE_KERNEL, attrs);
+}
+
+static void iommu_dma_free_noncontiguous(struct device *dev, size_t size,
+		struct page **pages, dma_addr_t dma_handle)
+{
+	__iommu_dma_unmap(dev, dma_handle, size);
+	__iommu_dma_free_pages(pages, PAGE_ALIGN(size) >> PAGE_SHIFT);
 }
+#endif
 
 static void iommu_dma_sync_single_for_cpu(struct device *dev,
 		dma_addr_t dma_handle, size_t size, enum dma_data_direction dir)
@@ -1074,7 +1080,7 @@  static int iommu_dma_mmap(struct device *dev, struct vm_area_struct *vma,
 		struct page **pages = dma_common_find_pages(cpu_addr);
 
 		if (pages)
-			return __iommu_dma_mmap(pages, size, vma);
+			return vm_map_pages(vma, pages, nr_pages);
 		pfn = vmalloc_to_pfn(cpu_addr);
 	} else {
 		pfn = page_to_pfn(virt_to_page(cpu_addr));
@@ -1124,6 +1130,10 @@  static const struct dma_map_ops iommu_dma_ops = {
 	.free			= iommu_dma_free,
 	.alloc_pages		= dma_common_alloc_pages,
 	.free_pages		= dma_common_free_pages,
+#ifdef CONFIG_DMA_REMAP
+	.alloc_noncontiguous	= iommu_dma_alloc_noncontiguous,
+	.free_noncontiguous	= iommu_dma_free_noncontiguous,
+#endif
 	.mmap			= iommu_dma_mmap,
 	.get_sgtable		= iommu_dma_get_sgtable,
 	.map_page		= iommu_dma_map_page,
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 3d1f91464bcf..3cc313678d42 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -22,6 +22,10 @@  struct dma_map_ops {
 			gfp_t gfp);
 	void (*free_pages)(struct device *dev, size_t size, struct page *vaddr,
 			dma_addr_t dma_handle, enum dma_data_direction dir);
+	struct page **(*alloc_noncontiguous)(struct device *dev, size_t size,
+			dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs);
+	void (*free_noncontiguous)(struct device *dev, size_t size,
+			struct page **pages, dma_addr_t dma_handle);
 	int (*mmap)(struct device *, struct vm_area_struct *,
 			void *, dma_addr_t, size_t, unsigned long attrs);
 
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 956151052d45..e1b4cb1d2e55 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -267,6 +267,11 @@  void *dma_alloc_noncoherent(struct device *dev, size_t size,
 		dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp);
 void dma_free_noncoherent(struct device *dev, size_t size, void *vaddr,
 		dma_addr_t dma_handle, enum dma_data_direction dir);
+bool dma_can_alloc_noncontiguous(struct device *dev);
+struct page **dma_alloc_noncontiguous(struct device *dev, size_t size,
+		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs);
+void dma_free_noncontiguous(struct device *dev, size_t size,
+		struct page **pages, dma_addr_t dma_handle);
 
 static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,
 		size_t size, enum dma_data_direction dir, unsigned long attrs)
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index d3032513c54b..770c2f66512d 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -530,6 +530,41 @@  void dma_free_noncoherent(struct device *dev, size_t size, void *vaddr,
 }
 EXPORT_SYMBOL_GPL(dma_free_noncoherent);
 
+bool dma_can_alloc_noncontiguous(struct device *dev)
+{
+	const struct dma_map_ops *ops = get_dma_ops(dev);
+
+	return ops && ops->free_noncontiguous;
+}
+EXPORT_SYMBOL_GPL(dma_can_alloc_noncontiguous);
+
+struct page **dma_alloc_noncontiguous(struct device *dev, size_t size,
+		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
+{
+	const struct dma_map_ops *ops = get_dma_ops(dev);
+
+	if (WARN_ON_ONCE(!dma_can_alloc_noncontiguous(dev)))
+		return NULL;
+	if (attrs & ~DMA_ATTR_ALLOC_SINGLE_PAGES) {
+		dev_warn(dev, "invalid flags (0x%lx) for %s\n",
+			 attrs, __func__);
+		return NULL;
+	}
+	return ops->alloc_noncontiguous(dev, size, dma_handle, gfp, attrs);
+}
+EXPORT_SYMBOL_GPL(dma_alloc_noncontiguous);
+
+void dma_free_noncontiguous(struct device *dev, size_t size,
+		struct page **pages, dma_addr_t dma_handle)
+{
+	const struct dma_map_ops *ops = get_dma_ops(dev);
+
+	if (WARN_ON_ONCE(!dma_can_alloc_noncontiguous(dev)))
+		return;
+	ops->free_noncontiguous(dev, size, pages, dma_handle);
+}
+EXPORT_SYMBOL_GPL(dma_free_noncontiguous);
+
 int dma_supported(struct device *dev, u64 mask)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);