iommu/mtk_iommu_v1: Implement an IDENTITY domain

What mtk does during mtk_iommu_v1_set_platform_dma() is actually putting
the iommu into identity mode. Make this available as a proper IDENTITY
domain.

The mtk_iommu_v1_def_domain_type() from
commit 8bbe13f5 ("iommu/mediatek-v1: Add def_domain_type") explains
this was needed to allow probe_finalize() to be called, but now the
IDENTITY domain will do the same job so change the returned
def_domain_type.

mkt_v1 is the only driver that returns IOMMU_DOMAIN_UNMANAGED from
def_domain_type().  This allows the next patch to enforce an IDENTITY
domain policy for this driver.
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/7-v8-81230027b2fa+9d-iommu_all_defdom_jgg@nvidia.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/mtk_iommu_v1.c

@@ -319,11 +319,27 @@ static int mtk_iommu_v1_attach_device(struct iommu_domain *domain, struct device
 	return 0;
 }
 
-static void mtk_iommu_v1_set_platform_dma(struct device *dev)
+static int mtk_iommu_v1_identity_attach(struct iommu_domain *identity_domain,
+					struct device *dev)
 {
 	struct mtk_iommu_v1_data *data = dev_iommu_priv_get(dev);
 
 	mtk_iommu_v1_config(data, dev, false);
+	return 0;
+}
+
+static struct iommu_domain_ops mtk_iommu_v1_identity_ops = {
+	.attach_dev = mtk_iommu_v1_identity_attach,
+};
+
+static struct iommu_domain mtk_iommu_v1_identity_domain = {
+	.type = IOMMU_DOMAIN_IDENTITY,
+	.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,
@@ -443,7 +459,7 @@ static int mtk_iommu_v1_create_mapping(struct device *dev, struct of_phandle_arg
 
 static int mtk_iommu_v1_def_domain_type(struct device *dev)
 {
-	return IOMMU_DOMAIN_UNMANAGED;
+	return IOMMU_DOMAIN_IDENTITY;
 }
 
 static struct iommu_device *mtk_iommu_v1_probe_device(struct device *dev)
@@ -578,6 +594,7 @@ static int mtk_iommu_v1_hw_init(const struct mtk_iommu_v1_data *data)
 }
 
 static const struct iommu_ops mtk_iommu_v1_ops = {
+	.identity_domain = &mtk_iommu_v1_identity_domain,
 	.domain_alloc	= mtk_iommu_v1_domain_alloc,
 	.probe_device	= mtk_iommu_v1_probe_device,
 	.probe_finalize = mtk_iommu_v1_probe_finalize,