diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 53174179102d17..a1a93990b3a211 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1771,15 +1771,35 @@ static int iommu_get_default_domain_type(struct iommu_group *group,
 	int type;
 
 	lockdep_assert_held(&group->mutex);
+
+	/*
+	 * ARM32 drivers supporting CONFIG_ARM_DMA_USE_IOMMU can declare an
+	 * identity_domain and it will automatically become their default
+	 * domain. Later on ARM_DMA_USE_IOMMU will install its UNMANAGED domain.
+	 * Override the selection to IDENTITY if we are sure the driver supports
+	 * it.
+	 */
+	if (IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU) && ops->identity_domain) {
+		type = IOMMU_DOMAIN_IDENTITY;
+		if (best_type && type && best_type != type)
+			return -1;
+		best_type = target_type = IOMMU_DOMAIN_IDENTITY;
+	}
+
 	for_each_group_device(group, gdev) {
 		type = best_type;
 		if (ops->def_domain_type) {
 			type = ops->def_domain_type(gdev->dev);
-			if (best_type && type && best_type != type)
+			if (best_type && type && best_type != type) {
+				/* Stick with the last driver override we saw */
+				best_type = type;
 				goto err;
+			}
 		}
 
-		if (dev_is_pci(gdev->dev) && to_pci_dev(gdev->dev)->untrusted) {
+		/* No ARM32 using systems will set untrusted, it cannot work. */
+		if (dev_is_pci(gdev->dev) && to_pci_dev(gdev->dev)->untrusted &&
+		    !WARN_ON(IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU))) {
 			type = IOMMU_DOMAIN_DMA;
 			if (best_type && type && best_type != type)
 				goto err;
@@ -1804,7 +1824,7 @@ static int iommu_get_default_domain_type(struct iommu_group *group,
 		"Device needs domain type %s, but device %s in the same iommu group requires type %s - using default\n",
 		iommu_domain_type_str(type), dev_name(last_dev),
 		iommu_domain_type_str(best_type));
-	return 0;
+	return best_type;
 }
 
 static void iommu_group_do_probe_finalize(struct device *dev)
diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
index cc3e7d53d33ad9..7c0c1d50df5f75 100644
--- a/drivers/iommu/mtk_iommu_v1.c
+++ b/drivers/iommu/mtk_iommu_v1.c
@@ -337,11 +337,6 @@ static struct iommu_domain mtk_iommu_v1_identity_domain = {
 	.ops = &mtk_iommu_v1_identity_ops,
 };
 
-static void mtk_iommu_v1_set_platform_dma(struct device *dev)
-{
-	mtk_iommu_v1_identity_attach(&mtk_iommu_v1_identity_domain, dev);
-}
-
 static int mtk_iommu_v1_map(struct iommu_domain *domain, unsigned long iova,
 			    phys_addr_t paddr, size_t pgsize, size_t pgcount,
 			    int prot, gfp_t gfp, size_t *mapped)
@@ -457,11 +452,6 @@ static int mtk_iommu_v1_create_mapping(struct device *dev, struct of_phandle_arg
 	return 0;
 }
 
-static int mtk_iommu_v1_def_domain_type(struct device *dev)
-{
-	return IOMMU_DOMAIN_IDENTITY;
-}
-
 static struct iommu_device *mtk_iommu_v1_probe_device(struct device *dev)
 {
 	struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
@@ -599,10 +589,8 @@ static const struct iommu_ops mtk_iommu_v1_ops = {
 	.probe_device	= mtk_iommu_v1_probe_device,
 	.probe_finalize = mtk_iommu_v1_probe_finalize,
 	.release_device	= mtk_iommu_v1_release_device,
-	.def_domain_type = mtk_iommu_v1_def_domain_type,
 	.device_group	= generic_device_group,
 	.pgsize_bitmap	= MT2701_IOMMU_PAGE_SIZE,
-	.set_platform_dma_ops = mtk_iommu_v1_set_platform_dma,
 	.owner          = THIS_MODULE,
 	.default_domain_ops = &(const struct iommu_domain_ops) {
 		.attach_dev	= mtk_iommu_v1_attach_device,
diff --git a/drivers/iommu/rockchip-iommu.c b/drivers/iommu/rockchip-iommu.c
index 033678f2f8b3ab..a582525d36f8cc 100644
--- a/drivers/iommu/rockchip-iommu.c
+++ b/drivers/iommu/rockchip-iommu.c
@@ -998,13 +998,6 @@ static struct iommu_domain rk_identity_domain = {
 	.ops = &rk_identity_ops,
 };
 
-#ifdef CONFIG_ARM
-static void rk_iommu_set_platform_dma(struct device *dev)
-{
-	WARN_ON(rk_iommu_identity_attach(&rk_identity_domain, dev));
-}
-#endif
-
 static int rk_iommu_attach_device(struct iommu_domain *domain,
 		struct device *dev)
 {
@@ -1183,9 +1176,6 @@ static const struct iommu_ops rk_iommu_ops = {
 	.probe_device = rk_iommu_probe_device,
 	.release_device = rk_iommu_release_device,
 	.device_group = rk_iommu_device_group,
-#ifdef CONFIG_ARM
-	.set_platform_dma_ops = rk_iommu_set_platform_dma,
-#endif
 	.pgsize_bitmap = RK_IOMMU_PGSIZE_BITMAP,
 	.of_xlate = rk_iommu_of_xlate,
 	.default_domain_ops = &(const struct iommu_domain_ops) {
