On 2017/9/4 23:59, Lorenzo Pieralisi wrote:

quoted

On Mon, Sep 04, 2017 at 08:33:22PM +0800, Zhou Wang wrote:

quoted

+to: Lorenzo

On 2017/8/31 22:21, Zhou Wang wrote:

quoted

Hi Will and Alex,

pci_request_acs is called in drivers/iommu/arm-smmu-v3.c to set pci_acs_enable.

PCI subsystem tries to enable ACS as below:

	pci_device_add
		--> pci_init_capabilities
			--> pci_enable_acs

in ACPI PCI driver. However, ACPI PCI driver will be called before SMMU v3 driver,
which will lead pci_enable_acs to return directly as pci_acs_enable is not set
before SMMU v3 driver loading.

I think this is a bug, what do you think about this problem?

I think that it is a bug that affects OF/ACPI alike. One way of solving

Yes, DT also has this problem.

quoted

it is requesting ACS at IORT init following appropriate checks (ie
mappings PCI->IOMMU - that would not solve the OF path though). I can
put together a quick fix, the overall problem needs some thinking
though.

I am not familiar with IORT init, but can we do it like:

diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index a3215ee..a6f1a21 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c

@@ -1131,6 +1131,7 @@ static void __init iort_init_platform_devices(void)

				acpi_free_fwnode_static(fwnode);
				return;
			}
+ 			pci_request_acs();
		}

		iort_node = ACPI_ADD_PTR(struct acpi_iort_node, iort_node,