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Commit b1d2dc00 authored by Nicolin Chen's avatar Nicolin Chen Committed by Christoph Hellwig
Browse files

dma-contiguous: add dma_{alloc,free}_contiguous() helpers 



Both dma_alloc_from_contiguous() and dma_release_from_contiguous() are
very simply implemented, but requiring callers to pass certain
parameters like count and align, and taking a boolean parameter to check
__GFP_NOWARN in the allocation flags. So every function call duplicates
similar work:

	unsigned long order = get_order(size);
	size_t count = size >> PAGE_SHIFT;

	page = dma_alloc_from_contiguous(dev, count, order,
			gfp & __GFP_NOWARN);

	[...]

	dma_release_from_contiguous(dev, page, size >> PAGE_SHIFT);

Additionally, as CMA can be used only in the context which permits
sleeping, most of callers do a gfpflags_allow_blocking() check and a
corresponding fallback allocation of normal pages upon any false result:

	if (gfpflags_allow_blocking(flag))
		page = dma_alloc_from_contiguous();
	if (!page)
		page = alloc_pages();

	[...]

	if (!dma_release_from_contiguous(dev, page, count))
		__free_pages(page, get_order(size));

So this patch simplifies those function calls by abstracting these
operations into the two new functions: dma_{alloc,free}_contiguous.

As some callers of dma_{alloc,release}_from_contiguous() might be
complicated, this patch just implements these two new functions to
kernel/dma/direct.c only as an initial step.

Suggested-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarNicolin Chen <nicoleotsuka@gmail.com>
Tested-by: default avatardann frazier <dann.frazier@canonical.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 1b961423

include/linux/dma-contiguous.h

+13 −0
Original line number Diff line number Diff line
@@ -111,6 +111,8 @@ struct page *dma_alloc_from_contiguous(struct device *dev, size_t count, 
				       unsigned int order, bool no_warn);

bool dma_release_from_contiguous(struct device *dev, struct page *pages,

				 int count);

struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp);

void dma_free_contiguous(struct device *dev, struct page *page, size_t size);



#else
@@ -153,6 +155,17 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages, 
	return false;

}



static inline struct page *dma_alloc_contiguous(struct device *dev, size_t size,

		gfp_t gfp)

{

	return NULL;

}



static inline void dma_free_contiguous(struct device *dev, struct page *page,

		size_t size)

{

}



#endif



#endif

kernel/dma/contiguous.c

+47 −0
Original line number Diff line number Diff line
@@ -214,6 +214,53 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages, 
	return cma_release(dev_get_cma_area(dev), pages, count);

}



/**

 * dma_alloc_contiguous() - allocate contiguous pages

 * @dev:   Pointer to device for which the allocation is performed.

 * @size:  Requested allocation size.

 * @gfp:   Allocation flags.

 *

 * This function allocates contiguous memory buffer for specified device. It

 * first tries to use device specific contiguous memory area if available or

 * the default global one, then tries a fallback allocation of normal pages.

 */

struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp)

{

	int node = dev ? dev_to_node(dev) : NUMA_NO_NODE;

	size_t count = PAGE_ALIGN(size) >> PAGE_SHIFT;

	size_t align = get_order(PAGE_ALIGN(size));

	struct cma *cma = dev_get_cma_area(dev);

	struct page *page = NULL;



	/* CMA can be used only in the context which permits sleeping */

	if (cma && gfpflags_allow_blocking(gfp)) {

		align = min_t(size_t, align, CONFIG_CMA_ALIGNMENT);

		page = cma_alloc(cma, count, align, gfp & __GFP_NOWARN);

	}



	/* Fallback allocation of normal pages */

	if (!page)

		page = alloc_pages_node(node, gfp, align);

	return page;

}



/**

 * dma_free_contiguous() - release allocated pages

 * @dev:   Pointer to device for which the pages were allocated.

 * @page:  Pointer to the allocated pages.

 * @size:  Size of allocated pages.

 *

 * This function releases memory allocated by dma_alloc_contiguous(). As the

 * cma_release returns false when provided pages do not belong to contiguous

 * area and true otherwise, this function then does a fallback __free_pages()

 * upon a false-return.

 */

void dma_free_contiguous(struct device *dev, struct page *page, size_t size)

{

	if (!cma_release(dev_get_cma_area(dev), page, size >> PAGE_SHIFT))

		__free_pages(page, get_order(size));

}



/*

 * Support for reserved memory regions defined in device tree

 */

kernel/dma/direct.c

+4 −20
Original line number Diff line number Diff line
@@ -96,8 +96,6 @@ static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size) 
struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,

		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)

{

	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;

	int page_order = get_order(size);

	struct page *page = NULL;

	u64 phys_mask;
@@ -109,20 +107,9 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size, 
	gfp |= __dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,

			&phys_mask);

again:

	/* CMA can be used only in the context which permits sleeping */

	if (gfpflags_allow_blocking(gfp)) {

		page = dma_alloc_from_contiguous(dev, count, page_order,

						 gfp & __GFP_NOWARN);

	page = dma_alloc_contiguous(dev, size, gfp);

	if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {

			dma_release_from_contiguous(dev, page, count);

			page = NULL;

		}

	}

	if (!page)

		page = alloc_pages_node(dev_to_node(dev), gfp, page_order);



	if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {

		__free_pages(page, page_order);

		dma_free_contiguous(dev, page, size);

		page = NULL;



		if (IS_ENABLED(CONFIG_ZONE_DMA32) &&
@@ -154,7 +141,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, 
	if (PageHighMem(page)) {

		/*

		 * Depending on the cma= arguments and per-arch setup

		 * dma_alloc_from_contiguous could return highmem pages.

		 * dma_alloc_contiguous could return highmem pages.

		 * Without remapping there is no way to return them here,

		 * so log an error and fail.

		 */
@@ -176,10 +163,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, 


void __dma_direct_free_pages(struct device *dev, size_t size, struct page *page)

{

	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;



	if (!dma_release_from_contiguous(dev, page, count))

		__free_pages(page, get_order(size));

	dma_free_contiguous(dev, page, size);

}



void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr,