drm/tegra: Detach devices from IOMMU DMA domain on arm32

All Tegra DRM devices are getting attached to an implicit IOMMU DMA
domain if CONFIG_ARM_DMA_USE_IOMMU=y. Since Tegra DRM driver manages IOMMU
by itself, the devices must be detached from the implicit domain using
arch-specific IOMMU-API. Note that this works only for arm32 and not for
arm64, which will remain broken if CONFIG_IOMMU_DMA is enabled.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
index 0ee924e3d0a1..552046062ec8 100644
--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c
@@ -15,6 +15,10 @@
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 
+#if IS_ENABLED(CONFIG_ARM_DMA_USE_IOMMU)
+#include <asm/dma-iommu.h>
+#endif
+
 #include "drm.h"
 #include "gem.h"
 
@@ -1068,6 +1072,14 @@ struct iommu_group *host1x_client_iommu_attach(struct host1x_client *client,
                 }
 
                 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);
+                        }
+#endif
                         err = iommu_attach_group(tegra->domain, group);
                         if (err < 0) {
                                 iommu_group_put(group);