From: Thierry Reding <treding@nvidia.com>
Date: Fri, 7 Nov 2014 15:26:18 +0000 (+0000)
Subject: iommu/arm-smmu: Play nice on non-ARM/SMMU systems
X-Git-Tag: Ubuntu-snapdragon-4.4.0-1029.32~7525^2^5^2~1
X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=0e7d37adbe45404a76d05d4ef11544f23cf639dd;p=mirror_ubuntu-zesty-kernel.git

iommu/arm-smmu: Play nice on non-ARM/SMMU systems

Currently the driver registers IOMMU bus operations for all busses even
if no ARM SMMU is present on a system. Depending on the driver probing
order this prevents the driver for the real IOMMU to register itself as
the bus-wide IOMMU.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
---

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index c8fc02f111c5..217581469f79 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -2075,8 +2075,20 @@ static struct platform_driver arm_smmu_driver = {
 
 static int __init arm_smmu_init(void)
 {
+	struct device_node *np;
 	int ret;
 
+	/*
+	 * Play nice with systems that don't have an ARM SMMU by checking that
+	 * an ARM SMMU exists in the system before proceeding with the driver
+	 * and IOMMU bus operation registration.
+	 */
+	np = of_find_matching_node(NULL, arm_smmu_of_match);
+	if (!np)
+		return 0;
+
+	of_node_put(np);
+
 	ret = platform_driver_register(&arm_smmu_driver);
 	if (ret)
 		return ret;