From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Mon, 17 Oct 2016 12:06:20 +0100 Subject: [PATCH 1/2] iommu/arm-smmu: Don't inadvertently reject multiple SMMUv3s Message-ID: <5cf1acbf9c42cc99e5cc0dacb50b7a92c3bd0feb.1476702234.git.robin.murphy@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org We now delay installing our per-bus iommu_ops until we know an SMMU has successfully probed, as they don't serve much purpose beforehand, and doing so also avoids fights between multiple IOMMU drivers in a single kernel. However, the upshot of passing the return value of bus_set_iommu() back from our probe function is that if there happens to be more than one SMMUv3 device in a system, the second and subsequent probes will wind up returning -EBUSY to the driver core and getting torn down again. There are essentially 3 cases in which bus_set_iommu() returns nonzero: 1. The bus already has iommu_ops installed 2. One of the add_device callbacks from the initial notifier failed 3. Allocating or installing the notifier itself failed The first two are down to devices other than the SMMU in question, so shouldn't abort an otherwise-successful SMMU probe, whilst the third is indicative of the kind of catastrophic system failure which isn't going to get much further anyway. Consequently, there is little harm in ignoring the return value either way. CC: Lorenzo Pieralisi Signed-off-by: Robin Murphy --- drivers/iommu/arm-smmu-v3.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index 15c01c3cd540..74fbef384deb 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -2637,16 +2637,13 @@ static int arm_smmu_device_dt_probe(struct platform_device *pdev) of_iommu_set_ops(dev->of_node, &arm_smmu_ops); #ifdef CONFIG_PCI pci_request_acs(); - ret = bus_set_iommu(&pci_bus_type, &arm_smmu_ops); - if (ret) - return ret; + bus_set_iommu(&pci_bus_type, &arm_smmu_ops); #endif #ifdef CONFIG_ARM_AMBA - ret = bus_set_iommu(&amba_bustype, &arm_smmu_ops); - if (ret) - return ret; + bus_set_iommu(&amba_bustype, &arm_smmu_ops); #endif - return bus_set_iommu(&platform_bus_type, &arm_smmu_ops); + bus_set_iommu(&platform_bus_type, &arm_smmu_ops); + return 0; } static int arm_smmu_device_remove(struct platform_device *pdev) -- 1.9.1