From 112c898b59dd5cfd95ee30dfe7cc4fc11a6d484e Mon Sep 17 00:00:00 2001 From: Wei Chen Date: Mon, 13 Jun 2016 17:20:17 +0800 Subject: [PATCH] iommu/arm-smmu: request pcie devices to enable ACS The PCIe ACS capability will affect the layout of iommu groups. Generally speaking, if the path from root port to the PCIe device is ACS enabled, the iommu will create a single iommu group for this PCIe device. If all PCIe devices on the path are ACS enabled then Linux can determine this path is ACS enabled. Linux use two PCIe configuration registers to determine the ACS status of PCIe devices: ACS Capability Register and ACS Control Register. The first register is used to check the implementation of ACS function of a PCIe device, the second register is used to check the enable status of ACS function. If one PCIe device has implemented and enabled the ACS function then Linux will determine this PCIe device enabled ACS. From the Chapter:6.12 of PCI Express Base Specification Revision 3.1a, we can find that when a PCIe device implements ACS function, the enable status is set to disabled by default and can be enabled by ACS-aware software. ACS will affect the iommu groups topology, so, the iommu driver is ACS-aware software. This patch adds a call to pci_request_acs() to the arm-smmu driver to enable the ACS function in PCIe devices that support it, when they get probed. Reviewed-by: Robin Murphy Reviewed-by: Eric Auger Signed-off-by: Wei Chen Signed-off-by: Will Deacon --- drivers/iommu/arm-smmu-v3.c | 2 ++ drivers/iommu/arm-smmu.c | 4 +++- 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c index 94b68213c50d..30ea89945543 100644 --- a/drivers/iommu/arm-smmu-v3.c +++ b/drivers/iommu/arm-smmu-v3.c @@ -2686,6 +2686,8 @@ static int __init arm_smmu_init(void) if (ret) return ret; + pci_request_acs(); + return bus_set_iommu(&pci_bus_type, &arm_smmu_ops); } diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c index 9345a3fcb706..ab365ec6184d 100644 --- a/drivers/iommu/arm-smmu.c +++ b/drivers/iommu/arm-smmu.c @@ -2096,8 +2096,10 @@ static int __init arm_smmu_init(void) #endif #ifdef CONFIG_PCI - if (!iommu_present(&pci_bus_type)) + if (!iommu_present(&pci_bus_type)) { + pci_request_acs(); bus_set_iommu(&pci_bus_type, &arm_smmu_ops); + } #endif return 0; -- 2.20.1