On Fri, 2015-07-03 at 17:44 +0100, Robin Murphy wrote:

On 03/07/15 10:27, Yong Wu wrote:
[...]

quoted

quoted

+/**
+ * iommu_dma_alloc - Allocate and map a buffer contiguous in IOVA space
+ * @dev: Device to allocate memory for. Must be a real device
+ *	 attached to an iommu_dma_domain
+ * @size: Size of buffer in bytes
+ * @gfp: Allocation flags
+ * @prot: IOMMU mapping flags
+ * @coherent: Which dma_mask to base IOVA allocation on
+ * @handle: Out argument for allocated DMA handle
+ * @flush_page: Arch callback to flush a single page from caches as
+ *		necessary. May be NULL for coherent allocations
+ *
+ * If @size is less than PAGE_SIZE, then a full CPU page will be allocated,
+ * but an IOMMU which supports smaller pages might not map the whole thing.
+ * For now, the buffer is unconditionally zeroed for compatibility
+ *
+ * Return: Array of struct page pointers describing the buffer,
+ *	   or NULL on failure.
+ */
+struct page **iommu_dma_alloc(struct device *dev, size_t size, gfp_t gfp,
+		int prot, bool coherent, dma_addr_t *handle,
+		void (*flush_page)(const void *, phys_addr_t))
+{
+	struct iommu_dma_domain *dom = arch_get_dma_domain(dev);
+	struct iova_domain *iovad = dom->iovad;
+	struct iova *iova;
+	struct page **pages;
+	struct sg_table sgt;
+	struct sg_mapping_iter miter;
+	dma_addr_t dma_addr;
+	unsigned int count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+
+	*handle = DMA_ERROR_CODE;

Hi Robin,

   Compare with the dma before, You delete this line here.

           size = PAGE_ALIGN(size);

   Do you expect the user should make sure the size must be aligned?

   so do __iommu_free_attrs.

Yeah, there is an oversight here due to some back-and-forth refactoring 
- both the page allocation and the IOVA allocation do get suitably 
aligned as they should, but the segments of the temporary scatterlist 
don't. Somehow I managed not to hit an iommu_map_sg failure due to that 
until some time after this posting (it seems most of the drivers I test 
with only make page-sized allocations...)

I've currently got the fixup below waiting for the next posting.

Robin.

Hi Robin,
    Could we know the status and ETA of the DMA next version.
    We are preparing the mtk-iommu next patch as our project request.
    We could help test it if you send the new patch.
    Thanks.

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+
+	/* IOMMU can map any pages, so himem can also be used here */
+	gfp |= __GFP_NOWARN | __GFP_HIGHMEM;
+	pages = __iommu_dma_alloc_pages(count, gfp);
+	if (!pages)
+		return NULL;
+
+	iova = __alloc_iova(dev, size, coherent);
+	if (!iova)
+		goto out_free_pages;
+

+	size = iova_align(iovad, size);

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+	if (sg_alloc_table_from_pages(&sgt, pages, count, 0, size, GFP_KERNEL))
+		goto out_free_iova;
+
+	dma_addr = iova_dma_addr(iovad, iova);
+	if (iommu_map_sg(dom->domain, dma_addr, sgt.sgl, sgt.orig_nents, prot)
+			< size)
+		goto out_free_sg;
+
+	/* Using the non-flushing flag since we're doing our own */
+	sg_miter_start(&miter, sgt.sgl, sgt.orig_nents, SG_MITER_FROM_SG);
+	while (sg_miter_next(&miter)) {
+		memset(miter.addr, 0, PAGE_SIZE);
+		if (flush_page)
+			flush_page(miter.addr, page_to_phys(miter.page));
+	}
+	sg_miter_stop(&miter);
+	sg_free_table(&sgt);
+
+	*handle = dma_addr;
+	return pages;
+
+out_free_sg:
+	sg_free_table(&sgt);
+out_free_iova:
+	__free_iova(iovad, iova);
+out_free_pages:
+	__iommu_dma_free_pages(pages, count);
+	return NULL;
+}
+

[...]

quoted

+
+#endif	/* __KERNEL__ */
+#endif	/* __DMA_IOMMU_H */