iommu/omap: Implement an IDENTITY domain

What omap does during omap_iommu_set_platform_dma() is actually putting
the iommu into identity mode.

Move to the new core support for ARM_DMA_USE_IOMMU by defining
ops->identity_domain.

This driver does not support IOMMU_DOMAIN_DMA, however it cannot be
compiled on ARM64 either. Most likely it is fine to support dma-iommu.c

Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/13-v8-81230027b2fa+9d-iommu_all_defdom_jgg@nvidia.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/omap-iommu.c

@@ -1555,16 +1555,31 @@ static void _omap_iommu_detach_dev(struct omap_iommu_domain *omap_domain,
 	omap_domain->dev = NULL;
 }
 
-static void omap_iommu_set_platform_dma(struct device *dev)
+static int omap_iommu_identity_attach(struct iommu_domain *identity_domain,
+				      struct device *dev)
 {
 	struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
-	struct omap_iommu_domain *omap_domain = to_omap_domain(domain);
+	struct omap_iommu_domain *omap_domain;
 
+	if (domain == identity_domain || !domain)
+		return 0;
+
+	omap_domain = to_omap_domain(domain);
 	spin_lock(&omap_domain->lock);
 	_omap_iommu_detach_dev(omap_domain, dev);
 	spin_unlock(&omap_domain->lock);
+	return 0;
 }
 
+static struct iommu_domain_ops omap_iommu_identity_ops = {
+	.attach_dev = omap_iommu_identity_attach,
+};
+
+static struct iommu_domain omap_iommu_identity_domain = {
+	.type = IOMMU_DOMAIN_IDENTITY,
+	.ops = &omap_iommu_identity_ops,
+};
+
 static struct iommu_domain *omap_iommu_domain_alloc(unsigned type)
 {
 	struct omap_iommu_domain *omap_domain;
@@ -1732,11 +1747,11 @@ static struct iommu_group *omap_iommu_device_group(struct device *dev)
 }
 
 static const struct iommu_ops omap_iommu_ops = {
+	.identity_domain = &omap_iommu_identity_domain,
 	.domain_alloc	= omap_iommu_domain_alloc,
 	.probe_device	= omap_iommu_probe_device,
 	.release_device	= omap_iommu_release_device,
 	.device_group	= omap_iommu_device_group,
-	.set_platform_dma_ops = omap_iommu_set_platform_dma,
 	.pgsize_bitmap	= OMAP_IOMMU_PGSIZES,
 	.default_domain_ops = &(const struct iommu_domain_ops) {
 		.attach_dev	= omap_iommu_attach_dev,