drm/tegra: Simplify IOMMU group selection

All the devices that make up the DRM device are now part of the same
IOMMU group. This simplifies the handling of the IOMMU attachment and
also avoids exhausting the number of IOMMUs available on early Tegra
SoC generations.

Signed-off-by: Thierry Reding <[e-mail]>

drivers/gpu/drm/tegra/dc.c

···
 	if (!dc->syncpt)
 		dev_warn(dc->dev, "failed to allocate syncpoint\n");
 
-	err = host1x_client_iommu_attach(client, true);
+	err = host1x_client_iommu_attach(client);
 	if (err < 0) {
 		dev_err(client->dev, "failed to attach to domain: %d\n", err);
 		return err;

drivers/gpu/drm/tegra/drm.c

···
 	return 0;
 }
 
-int host1x_client_iommu_attach(struct host1x_client *client, bool shared)
+int host1x_client_iommu_attach(struct host1x_client *client)
 {
 	struct drm_device *drm = dev_get_drvdata(client->parent);
 	struct tegra_drm *tegra = drm->dev_private;
···
 	int err;
 
 	if (tegra->domain) {
+		struct iommu_domain *domain;
+
 		group = iommu_group_get(client->dev);
 		if (!group) {
 			dev_err(client->dev, "failed to get IOMMU group\n");
 			return -ENODEV;
 		}
 
-		if (!shared || (shared && (group != tegra->group))) {
 #if IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU)
-			if (client->dev->archdata.mapping) {
-				struct dma_iommu_mapping *mapping =
-					to_dma_iommu_mapping(client->dev);
-				arm_iommu_detach_device(client->dev);
-				arm_iommu_release_mapping(mapping);
-			}
+		if (client->dev->archdata.mapping) {
+			struct dma_iommu_mapping *mapping =
+				to_dma_iommu_mapping(client->dev);
+			arm_iommu_detach_device(client->dev);
+			arm_iommu_release_mapping(mapping);
+		}
 #endif
+
+		domain = iommu_get_domain_for_dev(client->dev);
+		if (domain != tegra->domain) {
 			err = iommu_attach_group(tegra->domain, group);
 			if (err < 0) {
 				iommu_group_put(group);
 				return err;
 			}
-
-			if (shared && !tegra->group)
-				tegra->group = group;
 		}
 	}
 
···
 {
 	struct drm_device *drm = dev_get_drvdata(client->parent);
 	struct tegra_drm *tegra = drm->dev_private;
+	struct iommu_domain *domain;
 
 	if (client->group) {
-		if (client->group == tegra->group) {
+		/*
+		 * Devices that are part of the same group may no longer be
+		 * attached to a domain at this point because their group may
+		 * have been detached by an earlier client.
+		 */
+		domain = iommu_get_domain_for_dev(client->dev);
+		if (domain)
 			iommu_detach_group(tegra->domain, client->group);
-			tegra->group = NULL;
-		}
 
 		iommu_group_put(client->group);
 	}

drivers/gpu/drm/tegra/drm.h

···
 	struct drm_device *drm;
 
 	struct iommu_domain *domain;
-	struct iommu_group *group;
 	struct mutex mm_lock;
 	struct drm_mm mm;
 
···
 			      struct tegra_drm_client *client);
 int tegra_drm_unregister_client(struct tegra_drm *tegra,
 				struct tegra_drm_client *client);
-int host1x_client_iommu_attach(struct host1x_client *client, bool shared);
+int host1x_client_iommu_attach(struct host1x_client *client);
 void host1x_client_iommu_detach(struct host1x_client *client);
 
 int tegra_drm_init(struct tegra_drm *tegra, struct drm_device *drm);

drivers/gpu/drm/tegra/gr2d.c

···
 		goto put;
 	}
 
-	err = host1x_client_iommu_attach(client, false);
+	err = host1x_client_iommu_attach(client);
 	if (err < 0) {
 		dev_err(client->dev, "failed to attach to domain: %d\n", err);
 		goto free;

drivers/gpu/drm/tegra/gr3d.c

···
 		goto put;
 	}
 
-	err = host1x_client_iommu_attach(client, false);
+	err = host1x_client_iommu_attach(client);
 	if (err < 0) {
 		dev_err(client->dev, "failed to attach to domain: %d\n", err);
 		goto free;

drivers/gpu/drm/tegra/vic.c

···
 	struct vic *vic = to_vic(drm);
 	int err;
 
-	err = host1x_client_iommu_attach(client, false);
+	err = host1x_client_iommu_attach(client);
 	if (err < 0) {
 		dev_err(vic->dev, "failed to attach to domain: %d\n", err);
 		return err;