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Commit b737ca50 authored by Laura Abbott's avatar Laura Abbott Committed by Shiraz Hashim
Browse files

arm: Add option to skip buffer zeroing 



The DMA framework currently zeros all buffers because it (righfully so)
assumes that drivers will soon need to pass the memory to a device.
Some devices/use case may not require zeroed memory and there can
be an increase in performance if we skip the zeroing. Add a DMA_ATTR
to allow skipping of DMA zeroing.

Change-Id: Ib78a19cb341c3c441f91d5b004c6375c80c10413
Signed-off-by: default avatarLaura Abbott <lauraa@codeaurora.org>
parent 2d0f0840

arch/arm/mm/dma-mapping.c

+11 −12
Original line number Diff line number Diff line
@@ -307,7 +307,7 @@ static void __dma_free_buffer(struct page *page, size_t size) 
static void *__alloc_from_contiguous(struct device *dev, size_t size,

				     pgprot_t prot, struct page **ret_page,

				     const void *caller,

				     bool no_kernel_mapping);

				     struct dma_attrs *attrs);



static void *__alloc_remap_buffer(struct device *dev, size_t size, gfp_t gfp,

				 pgprot_t prot, struct page **ret_page,
@@ -375,7 +375,7 @@ static int __init atomic_pool_init(void) 


	if (IS_ENABLED(CONFIG_DMA_CMA))

		ptr = __alloc_from_contiguous(NULL, atomic_pool_size, prot,

				&page, atomic_pool_init, false);

				&page, atomic_pool_init, NULL);

	else

		ptr = __alloc_remap_buffer(NULL, atomic_pool_size, gfp, prot,

					   &page, atomic_pool_init);
@@ -559,17 +559,20 @@ static int __free_from_pool(void *start, size_t size) 
static void *__alloc_from_contiguous(struct device *dev, size_t size,

				     pgprot_t prot, struct page **ret_page,

				     const void *caller,

				     bool no_kernel_mapping)

				     struct dma_attrs *attrs)

{

	unsigned long order = get_order(size);

	size_t count = size >> PAGE_SHIFT;

	struct page *page;

	void *ptr;

	bool no_kernel_mapping = dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING,

							attrs);



	page = dma_alloc_from_contiguous(dev, count, order);

	if (!page)

		return NULL;



	if (!dma_get_attr(DMA_ATTR_SKIP_ZEROING, attrs))

		__dma_clear_buffer(page, size);



	if (PageHighMem(page)) {
@@ -655,7 +658,7 @@ static void *__alloc_simple_buffer(struct device *dev, size_t size, gfp_t gfp, 


static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle,

			 gfp_t gfp, pgprot_t prot, bool is_coherent,

			 const void *caller, bool no_kernel_mapping)

			 const void *caller, struct dma_attrs *attrs)

{

	u64 mask = get_coherent_dma_mask(dev);

	struct page *page = NULL;
@@ -696,7 +699,7 @@ static void *__dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, 
		addr = __alloc_remap_buffer(dev, size, gfp, prot, &page, caller);

	else

		addr = __alloc_from_contiguous(dev, size, prot, &page, caller,

						no_kernel_mapping);

						attrs);



	if (addr)

		*handle = pfn_to_dma(dev, page_to_pfn(page));
@@ -713,14 +716,12 @@ void *arm_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, 
{

	pgprot_t prot = __get_dma_pgprot(attrs, PAGE_KERNEL);

	void *memory;

	bool no_kernel_mapping = dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING,

					attrs);



	if (dma_alloc_from_coherent(dev, size, handle, &memory))

		return memory;



	return __dma_alloc(dev, size, handle, gfp, prot, false,

			   __builtin_return_address(0), no_kernel_mapping);

			   __builtin_return_address(0), attrs);

}



static void *arm_coherent_dma_alloc(struct device *dev, size_t size,
@@ -728,14 +729,12 @@ static void *arm_coherent_dma_alloc(struct device *dev, size_t size, 
{

	pgprot_t prot = __get_dma_pgprot(attrs, PAGE_KERNEL);

	void *memory;

	bool no_kernel_mapping = dma_get_attr(DMA_ATTR_NO_KERNEL_MAPPING,

					attrs);



	if (dma_alloc_from_coherent(dev, size, handle, &memory))

		return memory;



	return __dma_alloc(dev, size, handle, gfp, prot, true,

			   __builtin_return_address(0), no_kernel_mapping);

			   __builtin_return_address(0), attrs);

}



/*