dma-mapping: add a dma_alloc_noncontiguous API

Add a new API that returns a potentiall virtually non-contigous sg_table
and a DMA address.  This API is only properly implemented for dma-iommu
and will simply return a contigious chunk as a fallback.

The intent is that drivers can use this API if either:

 - no kernel mapping or only temporary kernel mappings are required.
   That is as a better replacement for DMA_ATTR_NO_KERNEL_MAPPING
 - a kernel mapping is required for cached and DMA mapped pages, but
   the driver also needs the pages to e.g. map them to userspace.
   In that sense it is a replacement for some aspects of the recently
   removed and never fully implemented DMA_ATTR_NON_CONSISTENT

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Tested-by: Ricardo Ribalda <ribalda@chromium.org>

diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst
index 157a474..00a1d4f 100644 (file)
--- a/Documentation/core-api/dma-api.rst
+++ b/Documentation/core-api/dma-api.rst
@@ -596,6 +596,84 @@ dma_alloc_noncoherent().
 
 ::
 
+       struct sg_table *
+       dma_alloc_noncontiguous(struct device *dev, size_t size,
+                               enum dma_data_direction dir, gfp_t gfp,
+                               unsigned long attrs);
+
+This routine allocates  <size> bytes of non-coherent and possibly non-contiguous
+memory.  It returns a pointer to struct sg_table that describes the allocated
+and DMA mapped memory, or NULL if the allocation failed. The resulting memory
+can be used for struct page mapped into a scatterlist are suitable for.
+
+The return sg_table is guaranteed to have 1 single DMA mapped segment as
+indicated by sgt->nents, but it might have multiple CPU side segments as
+indicated by sgt->orig_nents.
+
+The dir parameter specified if data is read and/or written by the device,
+see dma_map_single() for details.
+
+The gfp parameter allows the caller to specify the ``GFP_`` flags (see
+kmalloc()) for the allocation, but rejects flags used to specify a memory
+zone such as GFP_DMA or GFP_HIGHMEM.
+
+The attrs argument must be either 0 or DMA_ATTR_ALLOC_SINGLE_PAGES.
+
+Before giving the memory to the device, dma_sync_sgtable_for_device() needs
+to be called, and before reading memory written by the device,
+dma_sync_sgtable_for_cpu(), just like for streaming DMA mappings that are
+reused.
+
+::
+
+       void
+       dma_free_noncontiguous(struct device *dev, size_t size,
+                              struct sg_table *sgt,
+                              enum dma_data_direction dir)
+
+Free memory previously allocated using dma_alloc_noncontiguous().  dev, size,
+and dir must all be the same as those passed into dma_alloc_noncontiguous().
+sgt must be the pointer returned by dma_alloc_noncontiguous().
+
+::
+
+       void *
+       dma_vmap_noncontiguous(struct device *dev, size_t size,
+               struct sg_table *sgt)
+
+Return a contiguous kernel mapping for an allocation returned from
+dma_alloc_noncontiguous().  dev and size must be the same as those passed into
+dma_alloc_noncontiguous().  sgt must be the pointer returned by
+dma_alloc_noncontiguous().
+
+Once a non-contiguous allocation is mapped using this function, the
+flush_kernel_vmap_range() and invalidate_kernel_vmap_range() APIs must be used
+to manage the coherency between the kernel mapping, the device and user space
+mappings (if any).
+
+::
+
+       void
+       dma_vunmap_noncontiguous(struct device *dev, void *vaddr)
+
+Unmap a kernel mapping returned by dma_vmap_noncontiguous().  dev must be the
+same the one passed into dma_alloc_noncontiguous().  vaddr must be the pointer
+returned by dma_vmap_noncontiguous().
+
+
+::
+
+       int
+       dma_mmap_noncontiguous(struct device *dev, struct vm_area_struct *vma,
+                              size_t size, struct sg_table *sgt)
+
+Map an allocation returned from dma_alloc_noncontiguous() into a user address
+space.  dev and size must be the same as those passed into
+dma_alloc_noncontiguous().  sgt must be the pointer returned by
+dma_alloc_noncontiguous().
+
+::
+
        int
        dma_get_cache_alignment(void)
 

diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 51872e7..0d53a96 100644 (file)
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -22,6 +22,11 @@ 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 sg_table *(*alloc_noncontiguous)(struct device *dev, size_t size,
+                       enum dma_data_direction dir, gfp_t gfp,
+                       unsigned long attrs);
+       void (*free_noncontiguous)(struct device *dev, size_t size,
+                       struct sg_table *sgt, enum dma_data_direction dir);
        int (*mmap)(struct device *, struct vm_area_struct *,
                        void *, dma_addr_t, size_t, unsigned long attrs);
 
@@ -198,6 +203,20 @@ static inline int dma_mmap_from_global_coherent(struct vm_area_struct *vma,
 }
 #endif /* CONFIG_DMA_DECLARE_COHERENT */
 
+/*
+ * This is the actual return value from the ->alloc_noncontiguous method.
+ * The users of the DMA API should only care about the sg_table, but to make
+ * the DMA-API internal vmaping and freeing easier we stash away the page
+ * array as well (except for the fallback case).  This can go away any time,
+ * e.g. when a vmap-variant that takes a scatterlist comes along.
+ */
+struct dma_sgt_handle {
+       struct sg_table sgt;
+       struct page **pages;
+};
+#define sgt_handle(sgt) \
+       container_of((sgt), struct dma_sgt_handle, sgt)
+
 int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
                void *cpu_addr, dma_addr_t dma_addr, size_t size,
                unsigned long attrs);

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 2b8dce7..954847f 100644 (file)
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -144,6 +144,15 @@ u64 dma_get_required_mask(struct device *dev);
 size_t dma_max_mapping_size(struct device *dev);
 bool dma_need_sync(struct device *dev, dma_addr_t dma_addr);
 unsigned long dma_get_merge_boundary(struct device *dev);
+struct sg_table *dma_alloc_noncontiguous(struct device *dev, size_t size,
+               enum dma_data_direction dir, gfp_t gfp, unsigned long attrs);
+void dma_free_noncontiguous(struct device *dev, size_t size,
+               struct sg_table *sgt, enum dma_data_direction dir);
+void *dma_vmap_noncontiguous(struct device *dev, size_t size,
+               struct sg_table *sgt);
+void dma_vunmap_noncontiguous(struct device *dev, void *vaddr);
+int dma_mmap_noncontiguous(struct device *dev, struct vm_area_struct *vma,
+               size_t size, struct sg_table *sgt);
 #else /* CONFIG_HAS_DMA */
 static inline dma_addr_t dma_map_page_attrs(struct device *dev,
                struct page *page, size_t offset, size_t size,
@@ -257,6 +266,29 @@ static inline unsigned long dma_get_merge_boundary(struct device *dev)
 {
        return 0;
 }
+static inline struct sg_table *dma_alloc_noncontiguous(struct device *dev,
+               size_t size, enum dma_data_direction dir, gfp_t gfp,
+               unsigned long attrs)
+{
+       return NULL;
+}
+static inline void dma_free_noncontiguous(struct device *dev, size_t size,
+               struct sg_table *sgt, enum dma_data_direction dir)
+{
+}
+static inline void *dma_vmap_noncontiguous(struct device *dev, size_t size,
+               struct sg_table *sgt)
+{
+       return NULL;
+}
+static inline void dma_vunmap_noncontiguous(struct device *dev, void *vaddr)
+{
+}
+static inline int dma_mmap_noncontiguous(struct device *dev,
+               struct vm_area_struct *vma, size_t size, struct sg_table *sgt)
+{
+       return -EINVAL;
+}
 #endif /* CONFIG_HAS_DMA */
 
 struct page *dma_alloc_pages(struct device *dev, size_t size,

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 07f964e..2b06a80 100644 (file)
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -539,6 +539,112 @@ int dma_mmap_pages(struct device *dev, struct vm_area_struct *vma,
 }
 EXPORT_SYMBOL_GPL(dma_mmap_pages);
 
+static struct sg_table *alloc_single_sgt(struct device *dev, size_t size,
+               enum dma_data_direction dir, gfp_t gfp)
+{
+       struct sg_table *sgt;
+       struct page *page;
+
+       sgt = kmalloc(sizeof(*sgt), gfp);
+       if (!sgt)
+               return NULL;
+       if (sg_alloc_table(sgt, 1, gfp))
+               goto out_free_sgt;
+       page = __dma_alloc_pages(dev, size, &sgt->sgl->dma_address, dir, gfp);
+       if (!page)
+               goto out_free_table;
+       sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
+       sg_dma_len(sgt->sgl) = sgt->sgl->length;
+       return sgt;
+out_free_table:
+       sg_free_table(sgt);
+out_free_sgt:
+       kfree(sgt);
+       return NULL;
+}
+
+struct sg_table *dma_alloc_noncontiguous(struct device *dev, size_t size,
+               enum dma_data_direction dir, gfp_t gfp, unsigned long attrs)
+{
+       const struct dma_map_ops *ops = get_dma_ops(dev);
+       struct sg_table *sgt;
+
+       if (WARN_ON_ONCE(attrs & ~DMA_ATTR_ALLOC_SINGLE_PAGES))
+               return NULL;
+
+       if (ops && ops->alloc_noncontiguous)
+               sgt = ops->alloc_noncontiguous(dev, size, dir, gfp, attrs);
+       else
+               sgt = alloc_single_sgt(dev, size, dir, gfp);
+
+       if (sgt) {
+               sgt->nents = 1;
+               debug_dma_map_sg(dev, sgt->sgl, sgt->orig_nents, 1, dir);
+       }
+       return sgt;
+}
+EXPORT_SYMBOL_GPL(dma_alloc_noncontiguous);
+
+static void free_single_sgt(struct device *dev, size_t size,
+               struct sg_table *sgt, enum dma_data_direction dir)
+{
+       __dma_free_pages(dev, size, sg_page(sgt->sgl), sgt->sgl->dma_address,
+                        dir);
+       sg_free_table(sgt);
+       kfree(sgt);
+}
+
+void dma_free_noncontiguous(struct device *dev, size_t size,
+               struct sg_table *sgt, enum dma_data_direction dir)
+{
+       const struct dma_map_ops *ops = get_dma_ops(dev);
+
+       debug_dma_unmap_sg(dev, sgt->sgl, sgt->orig_nents, dir);
+       if (ops && ops->free_noncontiguous)
+               ops->free_noncontiguous(dev, size, sgt, dir);
+       else
+               free_single_sgt(dev, size, sgt, dir);
+}
+EXPORT_SYMBOL_GPL(dma_free_noncontiguous);
+
+void *dma_vmap_noncontiguous(struct device *dev, size_t size,
+               struct sg_table *sgt)
+{
+       const struct dma_map_ops *ops = get_dma_ops(dev);
+       unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+
+       if (ops && ops->alloc_noncontiguous)
+               return vmap(sgt_handle(sgt)->pages, count, VM_MAP, PAGE_KERNEL);
+       return page_address(sg_page(sgt->sgl));
+}
+EXPORT_SYMBOL_GPL(dma_vmap_noncontiguous);
+
+void dma_vunmap_noncontiguous(struct device *dev, void *vaddr)
+{
+       const struct dma_map_ops *ops = get_dma_ops(dev);
+
+       if (ops && ops->alloc_noncontiguous)
+               vunmap(vaddr);
+}
+EXPORT_SYMBOL_GPL(dma_vunmap_noncontiguous);
+
+int dma_mmap_noncontiguous(struct device *dev, struct vm_area_struct *vma,
+               size_t size, struct sg_table *sgt)
+{
+       const struct dma_map_ops *ops = get_dma_ops(dev);
+
+       if (ops && ops->alloc_noncontiguous) {
+               unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+
+               if (vma->vm_pgoff >= count ||
+                   vma_pages(vma) > count - vma->vm_pgoff)
+                       return -ENXIO;
+               return vm_map_pages(vma, sgt_handle(sgt)->pages, count);
+       }
+       return dma_mmap_pages(dev, vma, size, sg_page(sgt->sgl));
+}
+EXPORT_SYMBOL_GPL(dma_mmap_noncontiguous);
+
 int dma_supported(struct device *dev, u64 mask)
 {
        const struct dma_map_ops *ops = get_dma_ops(dev);