On 3/18/2016 8:12 AM, Robin Murphy wrote:

quoted

Since we know for sure that swiotlb_to_phys is a no-op on arm64, it might be cleaner to simply not reference it at all. I suppose we could have some private local wrappers, e.g.:

#define swiotlb_to_virt(addr) phys_to_virt((phys_addr_t)(addr))

to keep the intent of the code clear (and just in case anyone ever builds a system mad enough to warrant switching out that definition, but I'd hope that never happens).

Otherwise, looks good - thanks for doing this!

OK. I added this. Reviewed-by?

I'm not happy to submit such a big patch for all different ARCHs. I couldn't
find a cleaner solution. I'm willing to split this patch into multiple if there
is a better way.

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index ada00c3..8c0f66b 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c

@@ -29,6 +29,14 @@

 #include <asm/cacheflush.h>

+/*
+ * If you are building a system without IOMMU, then you are using SWIOTLB
+ * library. The ARM64 adaptation of this library does not support address
+ * translation and it assumes that physical address = dma address for such
+ * a use case. Please don't build a platform that violates this.
+ */

 static pgprot_t __get_dma_pgprot(struct dma_attrs *attrs, pgprot_t prot,
                                 bool coherent)
 {

@@ -188,7 +196,7 @@ static void __dma_free(struct device *dev, size_t size,
                       void *vaddr, dma_addr_t dma_handle,
                       struct dma_attrs *attrs)
 {
-       void *swiotlb_addr = phys_to_virt(swiotlb_dma_to_phys(dev, dma_handle));
+       void *swiotlb_addr = swiotlb_to_virt(dma_handle);

        size = PAGE_ALIGN(size);

@@ -209,8 +217,7 @@ static dma_addr_t __swiotlb_map_page(struct device *dev, struct page *page,

        dev_addr = swiotlb_map_page(dev, page, offset, size, dir, attrs);
        if (!is_device_dma_coherent(dev))
-               __dma_map_area(phys_to_virt(swiotlb_dma_to_phys(dev, dev_addr)),
-                              size, dir);
+               __dma_map_area(swiotlb_to_virt(dev_addr), size, dir);

        return dev_addr;
 }

@@ -283,8 +290,7 @@ static void __swiotlb_sync_single_for_device(struct device *dev,
 {
        swiotlb_sync_single_for_device(dev, dev_addr, size, dir);
        if (!is_device_dma_coherent(dev))
-               __dma_map_area(phys_to_virt(swiotlb_dma_to_phys(dev, dev_addr)),
-                              size, dir);
+               __dma_map_area(swiotlb_to_virt(dev_addr), size, dir);
 }




--

Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project