[PATCH 3/3] drm/tegra: Remove call to iommu_domain_alloc()

[Lu Baolu]

Commit <17de3f5fdd35> ("iommu: Retire bus ops") removes iommu ops from
the bus structure. The iommu subsystem no longer relies on bus for
operations. So iommu_domain_alloc() interface is no longer relevant.

Normally, iommu_paging_domain_alloc() could be a replacement for
iommu_domain_alloc() if the caller has the right device for IOMMU API
use. Unfortunately, this is not the case for this driver.

Iterate the devices on the platform bus and find a suitable device
whose device DMA is translated by an IOMMU. Then use this device to
allocate an iommu domain. The iommu subsystem prevents domains
allocated by one iommu driver from being attached to devices managed
by any different iommu driver.

Signed-off-by: Lu Baolu <baolu.lu at linux.intel.com>
Link: https://lore.kernel.org/r/20240610085555.88197-20-baolu.lu@linux.intel.com
---
 drivers/gpu/drm/tegra/drm.c | 34 +++++++++++++++++++++++++---------
 1 file changed, 25 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
index 03d1c76aec2d..ee391f859992 100644
--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c
@@ -1133,6 +1133,17 @@ static bool host1x_drm_wants_iommu(struct host1x_device *dev)
 	return domain != NULL;
 }
 
+static int iommu_mapped_device(struct device *dev, void *data)
+{
+	struct device **iommu_dev = data;
+
+	if (!device_iommu_mapped(dev))
+		return 0;
+
+	*iommu_dev = dev;
+	return 1;
+}
+
 static int host1x_drm_probe(struct host1x_device *dev)
 {
 	struct tegra_drm *tegra;
@@ -1149,16 +1160,21 @@ static int host1x_drm_probe(struct host1x_device *dev)
 		goto put;
 	}
 
-	if (host1x_drm_wants_iommu(dev) && iommu_present(&platform_bus_type)) {
-		tegra->domain = iommu_domain_alloc(&platform_bus_type);
-		if (!tegra->domain) {
-			err = -ENOMEM;
-			goto free;
+	if (host1x_drm_wants_iommu(dev)) {
+		struct device *iommu_dev = NULL;
+
+		bus_for_each_dev(&platform_bus_type, NULL, &iommu_dev, iommu_mapped_device);
+		if (iommu_dev) {
+			tegra->domain = iommu_paging_domain_alloc(iommu_dev);
+			if (IS_ERR(tegra->domain)) {
+				err = PTR_ERR(tegra->domain);
+				goto free;
+			}
+
+			err = iova_cache_get();
+			if (err < 0)
+				goto domain;
 		}
-
-		err = iova_cache_get();
-		if (err < 0)
-			goto domain;
 	}
 
 	mutex_init(&tegra->clients_lock);
-- 
2.34.1