[PATCH v2 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. In such a case IOVAs
can be allocated from anywhere in the domain's geometry, so also add a
check to ensure the device's dma-ranges cover it. Presently, this is the
case for all platforms except some OMAP platforms with a non-zero
dma-ranges base.

Signed-off-by: Mikko Perttunen <mperttunen@xxxxxxxxxx>
---
 arch/arm/mm/dma-mapping.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index f2d3e8ec3487..d6315baeddb9 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1761,13 +1761,33 @@ 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;
 
 	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;
 	}
+
+	/*
+	 * An existing cookie means the core owns the domain. Only set the
+	 * per-binding DMA ops. IOVAs are allocated from the whole aperture,
+	 * so the device's dma-ranges must cover it.
+	 */
+	if (mapping) {
+		const struct iommu_domain_geometry *geo =
+			&mapping->domain->geometry;
+
+		if (dma_base > geo->aperture_start ||
+		    dma_base + size < geo->aperture_end) {
+			dev_err(dev, "dma-ranges do not cover the IOMMU aperture\n");
+			return;
+		}
+
+		set_dma_ops(dev, &iommu_ops);
+		return;
+	}
+
 	mapping = arm_iommu_create_mapping(dev, dma_base, size);
 	if (IS_ERR(mapping)) {
 		pr_warn("Failed to create %llu-byte IOMMU mapping for device %s\n",
@@ -1792,6 +1812,9 @@ 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