[PATCH 1/2] arm64: dma-mapping: implement dma_get_sgtable()

[Robin Murphy]

The default dma_common_get_sgtable() implementation relies on the CPU
address of the buffer being a regular lowmem address. This is not always
the case on arm64, since allocations from the various DMA pools may have
remapped vmalloc addresses, rendering the use of virt_to_page() invalid.

Fix this by providing our own implementation based on the fact that we
can safely derive a physical address from the DMA address in both cases.

CC: Jon Medhurst <tixy at linaro.org>
Signed-off-by: Robin Murphy <robin.murphy at arm.com>
---
 arch/arm64/mm/dma-mapping.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index d16a1ce..4b9b600 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -337,10 +337,24 @@ static int __swiotlb_mmap(struct device *dev,
 	return __dma_common_mmap(dev, vma, cpu_addr, dma_addr, size);
 }
 
+int __swiotlb_get_sgtable(struct device *dev, struct sg_table *sgt,
+			  void *cpu_addr, dma_addr_t handle, size_t size,
+			  struct dma_attrs *attrs)
+{
+	int ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
+
+	if (!ret)
+		sg_set_page(sgt->sgl, phys_to_page(dma_to_phys(dev, handle)),
+			    PAGE_ALIGN(size), 0);
+
+	return ret;
+}
+
 static struct dma_map_ops swiotlb_dma_ops = {
 	.alloc = __dma_alloc,
 	.free = __dma_free,
 	.mmap = __swiotlb_mmap,
+	.get_sgtable = __swiotlb_get_sgtable,
 	.map_page = __swiotlb_map_page,
 	.unmap_page = __swiotlb_unmap_page,
 	.map_sg = __swiotlb_map_sg_attrs,
-- 
1.9.1