arm64: dma-mapping: Fix IOMMU breakage

My forward-port of the arm64 pcie bounce buffer support broke builds
with IOMMU support enabled.

Fixes: 53f58fe ("Ported pcie-brcmstb bounce buffer implementation to ARM64. (#3144)")

Signed-off-by: Phil Elwell <phil@raspberrypi.org>

arch/arm64/mm/dma-mapping.c

@@ -160,6 +160,37 @@ void arch_sync_dma_for_cpu(struct device *dev, phys_addr_t paddr,
  __dma_unmap_area(phys_to_virt(paddr), size, dir);
 }
 
+#ifdef CONFIG_IOMMU_DMA
+static int __swiotlb_get_sgtable_page(struct sg_table *sgt,
+ struct page *page, size_t size)
+{
+ int ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
+
+ if (!ret)
+ sg_set_page(sgt->sgl, page, PAGE_ALIGN(size), 0);
+
+ return ret;
+}
+
+static int __swiotlb_mmap_pfn(struct vm_area_struct *vma,
+ unsigned long pfn, size_t size)
+{
+ int ret = -ENXIO;
+ unsigned long nr_vma_pages = vma_pages(vma);
+ unsigned long nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
+ unsigned long off = vma->vm_pgoff;
+
+ if (off < nr_pages && nr_vma_pages <= (nr_pages - off)) {
+ ret = remap_pfn_range(vma, vma->vm_start,
+ pfn + off,
+ vma->vm_end - vma->vm_start,
+ vma->vm_page_prot);
+ }
+
+ return ret;
+}
+#endif /* CONFIG_IOMMU_DMA */
+
 static int __init atomic_pool_init(void)
 {
  pgprot_t prot = __pgprot(PROT_NORMAL_NC);