From: Thierry Reding <treding@nvidia.com>
Date: Sat, 17 Mar 2018 01:52:38 +0100
Subject: drm/tegra: dc: Detach IOMMU group from domain only once
Git-commit: b1d0b34b748c9e5e67a91c545cb48711cfde119c
Patch-mainline: v4.16-rc7
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

Detaching from an IOMMU group multiple times can lead to a crash. This
could potentially be fixed in the IOMMU driver, but it's easy to avoid
the subsequent detach operations in this driver, so do that as well.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/tegra/dc.c |   16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/tegra/dc.c
+++ b/drivers/gpu/drm/tegra/dc.c
@@ -1903,8 +1903,12 @@ cleanup:
 	if (!IS_ERR(primary))
 		drm_plane_cleanup(primary);
 
-	if (group && tegra->domain) {
-		iommu_detach_group(tegra->domain, group);
+	if (group && dc->domain) {
+		if (group == tegra->group) {
+			iommu_detach_group(dc->domain, group);
+			tegra->group = NULL;
+		}
+
 		dc->domain = NULL;
 	}
 
@@ -1913,8 +1917,10 @@ cleanup:
 
 static int tegra_dc_exit(struct host1x_client *client)
 {
+	struct drm_device *drm = dev_get_drvdata(client->parent);
 	struct iommu_group *group = iommu_group_get(client->dev);
 	struct tegra_dc *dc = host1x_client_to_dc(client);
+	struct tegra_drm *tegra = drm->dev_private;
 	int err;
 
 	devm_free_irq(dc->dev, dc->irq, dc);
@@ -1926,7 +1932,11 @@ static int tegra_dc_exit(struct host1x_c
 	}
 
 	if (group && dc->domain) {
-		iommu_detach_group(dc->domain, group);
+		if (group == tegra->group) {
+			iommu_detach_group(dc->domain, group);
+			tegra->group = NULL;
+		}
+
 		dc->domain = NULL;
 	}