[PATCH rc] drm/tegra: Do not assume that a NULL domain means no DMA IOMMU

[Jason Gunthorpe]

Previously with tegra-smmu, even with CONFIG_IOMMU_DMA, the default domain
could have been left as NULL. The NULL domain is specially recognized by
host1x_client_iommu_attach() as meaning it is not the DMA domain and
should be replaced with the special shared domain.

This happened prior to the below commit because tegra-smmu was using the
NULL domain to mean IDENTITY.

Now that the domain is properly labled the test in DRM doesn't see NULL.
Check for IDENTITY as well to enable the special domains.

Fixes: c8cc2655cc6c ("iommu/tegra-smmu: Implement an IDENTITY domain")
Reported-by: diogo.ivo at tecnico.ulisboa.pt
Closes: https://lore.kernel.org/all/bbmhcoghrprmbdibnjum6lefix2eoquxrde7wyqeulm4xabmlm@b6jy32saugqh/
Tested-by: diogo.ivo at tecnico.ulisboa.pt
Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
---
 drivers/gpu/drm/tegra/drm.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
index ff36171c8fb700..a73cff7a307082 100644
--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c
@@ -960,7 +960,8 @@ int host1x_client_iommu_attach(struct host1x_client *client)
 	 * not the shared IOMMU domain, don't try to attach it to a different
 	 * domain. This allows using the IOMMU-backed DMA API.
 	 */
-	if (domain && domain != tegra->domain)
+	if (domain && domain->type != IOMMU_DOMAIN_IDENTITY &&
+	    domain != tegra->domain)
 		return 0;
 
 	if (tegra->domain) {

base-commit: 755bd21c4a64124e9c85a77e742df3073eac9a41
-- 
2.43.0