[PATCH 05/11] ARM: dma-mapping: Bypass the legacy path for core-owned DMA API domains

[Mikko Perttunen]

ARM's arch_setup_dma_ops / arm_setup_iommu_dma_ops creates a custom
IOMMU domain for DMA API usage, and continues to do so when the IOMMU
driver doesn't explicitly request a DMA default domain type.

When, however, that DMA default domain is requested and the core owns
the domain, we need to skip our own domain management. Add checks to
arm_setup/teardown_iommu_dma_ops for these cases.

Signed-off-by: Mikko Perttunen <mperttunen at nvidia.com>
---
 arch/arm/mm/dma-mapping.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index e0d58778c5f5..91f12fb91509 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1761,9 +1761,18 @@ EXPORT_SYMBOL_GPL(arm_iommu_detach_device);
 
 static void arm_setup_iommu_dma_ops(struct device *dev)
 {
-	struct dma_iommu_mapping *mapping;
+	struct dma_iommu_mapping *mapping = to_dma_iommu_mapping(dev);
 	u64 dma_base = 0, size = 1ULL << 32;
 
+	/*
+	 * An existing cookie means the core owns the domain. Only set the
+	 * per-binding DMA ops.
+	 */
+	if (mapping) {
+		set_dma_ops(dev, &iommu_ops);
+		return;
+	}
+
 	if (dev->dma_range_map) {
 		dma_base = dma_range_map_min(dev->dma_range_map);
 		size = dma_range_map_max(dev->dma_range_map) - dma_base;
@@ -1792,6 +1801,9 @@ static void arm_teardown_iommu_dma_ops(struct device *dev)
 	if (!mapping)
 		return;
 
+	if (!mapping->owns_domain)
+		return;
+
 	arm_iommu_detach_device(dev);
 	arm_iommu_release_mapping(mapping);
 }

-- 
2.55.0