From: Thierry Reding <treding@nvidia.com>
Date: Mon, 11 May 2020 18:10:00 +0200
Subject: iommu: Do not probe devices on IOMMU-less busses
Git-commit: f38338cf0691b5fae5f9a46d188eef92ab9e6296
Patch-mainline: v5.8-rc1
References: bsc#1175713

The host1x bus implemented on Tegra SoCs is primarily an abstraction to
create logical device from multiple platform devices. Since the devices
in such a setup are typically hierarchical, DMA setup still needs to be
done so that DMA masks can be properly inherited, but we don't actually
want to attach the host1x logical devices to any IOMMU. The platform
devices that make up the logical device are responsible for memory bus
transactions, so it is them that will need to be attached to the IOMMU.

Add a check to __iommu_probe_device() that aborts IOMMU setup early for
busses that don't have the IOMMU operations pointer set since they will
cause a crash otherwise.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20200511161000.3853342-1-thierry.reding@gmail.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/iommu/iommu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index a9e5618cde80..9d1d917e1050 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -195,6 +195,9 @@ static int __iommu_probe_device(struct device *dev, struct list_head *group_list
 	struct iommu_group *group;
 	int ret;
 
+	if (!ops)
+		return -ENODEV;
+
 	if (!dev_iommu_get(dev))
 		return -ENOMEM;