[PATCHv2 2/3] arm64: Support DMA_ATTR_WRITE_COMBINE

[Laura Abbott]

DMA_ATTR_WRITE_COMBINE is currently ignored. Set the pgprot
appropriately for non coherent opperations.

Signed-off-by: Laura Abbott <lauraa at codeaurora.org>
---
 arch/arm64/mm/dma-mapping.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index 0cdd2f6..608c343 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -29,6 +29,17 @@
 struct dma_map_ops *dma_ops;
 EXPORT_SYMBOL(dma_ops);
 
+
+static inline pgprot_t __get_dma_pgprot(struct dma_attrs *attrs, pgprot_t prot,
+					bool coherent)
+{
+	if (dma_get_attr(DMA_ATTR_WRITE_COMBINE, attrs))
+		return pgprot_writecombine(prot)
+	else if (!coherent)
+		return pgprot_dmacoherent(prot);
+	return prot;
+}
+
 static void *arm64_swiotlb_alloc_coherent(struct device *dev, size_t size,
 					  dma_addr_t *dma_handle, gfp_t flags,
 					  struct dma_attrs *attrs)
@@ -72,7 +83,7 @@ static void *arm64_swiotlb_alloc_noncoherent(struct device *dev, size_t size,
 	for (i = 0; i < (size >> PAGE_SHIFT); i++)
 		map[i] = page + i;
 	coherent_ptr = vmap(map, size >> PAGE_SHIFT, VM_MAP,
-			    pgprot_dmacoherent(pgprot_default));
+			    __get_dma_pgprot(attrs, pgprot_default, false));
 	kfree(map);
 	if (!coherent_ptr)
 		goto no_map;
@@ -223,7 +234,7 @@ static int arm64_swiotlb_mmap_noncoherent(struct device *dev,
 		void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		struct dma_attrs *attrs)
 {
-	vma->vm_page_prot = pgprot_dmacoherent(vma->vm_page_prot);
+	vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot, false);
 	return __dma_common_mmap(dev, vma, cpu_addr, dma_addr, size);
 }
 
-- 
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