[PATCH 2/2] iommu/dma: Skip iova_to_phys() on unmap when unneeded

[Joe Damato]

iommu_dma_unmap_phys() looks up the physical address of every mapping
with iommu_iova_to_phys() before unmapping it.

This is unneeded for a coherent device that does not use a swiotlb.
Skipping this saves a page table walk.

iommu_dma_sync_single_for_cpu() already skips the walk for these
devices, so do the same in iommu_dma_unmap_phys().

Signed-off-by: Joe Damato <joe@xxxxxxx>
---
 drivers/iommu/dma-iommu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index a25ee287a5ac..c4a5fac4f7cb 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1260,9 +1260,11 @@ dma_addr_t iommu_dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
 void iommu_dma_unmap_phys(struct device *dev, dma_addr_t dma_handle,
 		size_t size, enum dma_data_direction dir, unsigned long attrs)
 {
+	unsigned long skip_phys;
 	phys_addr_t phys;
 
-	if (attrs & (DMA_ATTR_MMIO | DMA_ATTR_REQUIRE_COHERENT)) {
+	skip_phys = attrs & (DMA_ATTR_MMIO | DMA_ATTR_REQUIRE_COHERENT);
+	if (skip_phys || dev_is_coherent_no_swiotlb(dev, size, dir)) {
 		__iommu_dma_unmap(dev, dma_handle, size);
 		return;
 	}
-- 
2.53.0-Meta