Commit 7d5b5738 authored by Christoph Hellwig's avatar Christoph Hellwig
Browse files

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: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarTomasz Figa <tfiga@chromium.org>
Tested-by: default avatarRicardo Ribalda <ribalda@chromium.org>
parent 198c50e2

Documentation/core-api/dma-api.rst

+78 −0
Original line number Diff line number Diff line
@@ -594,6 +594,84 @@ dev, size, dma_handle and dir must all be the same as those passed into 
dma_alloc_noncoherent().  cpu_addr must be the virtual address returned by

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

include/linux/dma-map-ops.h

+19 −0
Original line number Diff line number Diff line
@@ -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);

include/linux/dma-mapping.h

+32 −0
Original line number Diff line number Diff line
@@ -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,

kernel/dma/mapping.c

+106 −0
Original line number Diff line number Diff line
@@ -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);