[PATCH 02/10] arm64/iommu: don't remap contiguous allocations for coherent devices

[Christoph Hellwig]

There is no need to have an additional kernel mapping for a contiguous
allocation if the device already is DMA coherent, so skip it.

Signed-off-by: Christoph Hellwig <h...@lst.de>
---
 arch/arm64/mm/dma-mapping.c | 35 ++++++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index 4c0f498069e8..d39b60113539 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -255,13 +255,18 @@ static void *__iommu_alloc_attrs(struct device *dev, 
size_t size,
                                                    size >> PAGE_SHIFT);
                        return NULL;
                }
+
+               if (coherent) {
+                       memset(addr, 0, size);
+                       return addr;
+               }
+
                addr = dma_common_contiguous_remap(page, size, VM_USERMAP,
                                                   prot,
                                                   __builtin_return_address(0));
                if (addr) {
                        memset(addr, 0, size);
-                       if (!coherent)
-                               __dma_flush_area(page_to_virt(page), iosize);
+                       __dma_flush_area(page_to_virt(page), iosize);
                } else {
                        iommu_dma_unmap_page(dev, *handle, iosize, 0, attrs);
                        dma_release_from_contiguous(dev, page,
@@ -309,7 +314,9 @@ static void __iommu_free_attrs(struct device *dev, size_t 
size, void *cpu_addr,
 
                iommu_dma_unmap_page(dev, handle, iosize, 0, attrs);
                dma_release_from_contiguous(dev, page, size >> PAGE_SHIFT);
-               dma_common_free_remap(cpu_addr, size, VM_USERMAP);
+
+               if (!dev_is_dma_coherent(dev))
+                       dma_common_free_remap(cpu_addr, size, VM_USERMAP);
        } else if (is_vmalloc_addr(cpu_addr)){
                struct vm_struct *area = find_vm_area(cpu_addr);
 
@@ -336,11 +343,12 @@ static int __iommu_mmap_attrs(struct device *dev, struct 
vm_area_struct *vma,
                return ret;
 
        if (attrs & DMA_ATTR_FORCE_CONTIGUOUS) {
-               /*
-                * DMA_ATTR_FORCE_CONTIGUOUS allocations are always remapped,
-                * hence in the vmalloc space.
-                */
-               unsigned long pfn = vmalloc_to_pfn(cpu_addr);
+               unsigned long pfn;
+
+               if (dev_is_dma_coherent(dev))
+                       pfn = virt_to_pfn(cpu_addr);
+               else
+                       pfn = vmalloc_to_pfn(cpu_addr);
                return __swiotlb_mmap_pfn(vma, pfn, size);
        }
 
@@ -359,11 +367,12 @@ static int __iommu_get_sgtable(struct device *dev, struct 
sg_table *sgt,
        struct vm_struct *area = find_vm_area(cpu_addr);
 
        if (attrs & DMA_ATTR_FORCE_CONTIGUOUS) {
-               /*
-                * DMA_ATTR_FORCE_CONTIGUOUS allocations are always remapped,
-                * hence in the vmalloc space.
-                */
-               struct page *page = vmalloc_to_page(cpu_addr);
+               struct page *page;
+
+               if (dev_is_dma_coherent(dev))
+                       page = virt_to_page(cpu_addr);
+               else
+                       page = vmalloc_to_page(cpu_addr);
                return __swiotlb_get_sgtable_page(sgt, page, size);
        }
 
-- 
2.19.2

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