[Question] PCI ACS is broken for ARM SMMU v3?
wangzhou1 at hisilicon.com
Tue Sep 5 05:47:15 PDT 2017
On 2017/9/4 23:59, Lorenzo Pieralisi wrote:
> On Mon, Sep 04, 2017 at 08:33:22PM +0800, Zhou Wang wrote:
>> +to: Lorenzo
>> On 2017/8/31 22:21, Zhou Wang wrote:
>>> 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_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.
> 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
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
@@ -1131,6 +1131,7 @@ static void __init iort_init_platform_devices(void)
iort_node = ACPI_ADD_PTR(struct acpi_iort_node, iort_node,
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