dma: Take into account dma_pfn_offset (25f1e188) · Commits · 戴 / test

Even though dma-noop-ops assumes 1:1 memory mapping DMA memory range can be different to RAM. For example, ARM STM32F4 MCU offers the possibility to remap SDRAM from 0xc000_0000 to 0x0 to get CPU performance boost, but DMA continue to see SDRAM at 0xc000_0000. This difference in mapping is handled via device-tree "dma-range" property which leads to dev->dma_pfn_offset is set nonzero. To handle such cases take dma_pfn_offset into account. Cc: Joerg Roedel <jroedel@suse.de> Cc: Christian Borntraeger <borntraeger@de.ibm.com> Reported-by:

Benjamin Gaignard <benjamin.gaignard@linaro.org> Tested-by:

Andras Szemzo <sza@esh.hu> Tested-by:

Alexandre TORGUE <alexandre.torgue@st.com> Reviewed-by:

Robin Murphy <robin.murphy@arm.com> Signed-off-by:

Vladimir Murzin <vladimir.murzin@arm.com> Signed-off-by:

Christoph Hellwig <hch@lst.de>

lib/dma-noop.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -7,6 +7,7 @@
		#include <linux/mm.h>
		#include <linux/dma-mapping.h>
		#include <linux/scatterlist.h>
		#include <linux/pfn.h>

		static void dma_noop_alloc(struct device dev, size_t size,
		dma_addr_t *dma_handle, gfp_t gfp,
		@@ -16,7 +17,8 @@ static void dma_noop_alloc(struct device dev, size_t size,

		ret = (void *)__get_free_pages(gfp, get_order(size));
		if (ret)
		*dma_handle = virt_to_phys(ret);
		*dma_handle = virt_to_phys(ret) - PFN_PHYS(dev->dma_pfn_offset);

		return ret;
		}

		@@ -32,7 +34,7 @@ static dma_addr_t dma_noop_map_page(struct device dev, struct page page,
		enum dma_data_direction dir,
		unsigned long attrs)
		{
		return page_to_phys(page) + offset;
		return page_to_phys(page) + offset - PFN_PHYS(dev->dma_pfn_offset);
		}

		static int dma_noop_map_sg(struct device dev, struct scatterlist sgl, int nents,
		@@ -43,11 +45,12 @@ static int dma_noop_map_sg(struct device dev, struct scatterlist sgl, int nent
		struct scatterlist *sg;

		for_each_sg(sgl, sg, nents, i) {
		dma_addr_t offset = PFN_PHYS(dev->dma_pfn_offset);
		void *va;

		BUG_ON(!sg_page(sg));
		va = sg_virt(sg);
		sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va);
		sg_dma_address(sg) = (dma_addr_t)virt_to_phys(va) - offset;
		sg_dma_len(sg) = sg->length;
		}

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