On 2017/9/20 1:05, Lorenzo Pieralisi wrote:
> commit f6810c15cf97 ("iommu/arm-smmu: Clean up early-probing
> workarounds") removed kernel code that was allowing to initialize
> and probe the SMMU devices early (ie earlier than PCI devices through
> linker script callback entries) in the boot process because it was not
> needed any longer in that the SMMU devices/drivers now support deferred
> probing.
>
> Since the SMMUs probe routines are also in charge of requesting global
> PCI ACS kernel enablement, commit f6810c15cf97 ("iommu/arm-smmu: Clean
> up early-probing workarounds") also postponed PCI ACS enablement to
> SMMUs devices probe time, which may be too late given that PCI devices
> needs to detect if PCI ACS is enabled to init the respective capability
> through the following call path:
>
> pci_device_add()
> -> pci_init_capabilities()
> -> pci_enable_acs()
>
> Add code in the ACPI IORT SMMU platform devices initialization path
> (that is called before ACPI PCI enumeration) to detect if an SMMU is
> present in HW and enable PCI ACS if it actually is, restoring the
> correct PCI ACS enablement sequencing.
>
> Fixes: f6810c15cf97 ("iommu/arm-smmu: Clean up early-probing
> Signed-workarounds")
> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> Cc: Robin Murphy <robin.murphy@xxxxxxx>
> Cc: Zhou Wang <wangzhou1@xxxxxxxxxxxxx>
> Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
> ---
> drivers/acpi/arm64/iort.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index 9565d57..71a7694 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -1184,6 +1184,7 @@ static void __init iort_init_platform_devices(void)
> struct acpi_table_iort *iort;
> struct fwnode_handle *fwnode;
> int i, ret;
> + bool smmu_detected = false;
>
> /*
> * iort_table and iort both point to the start of IORT table, but
> @@ -1218,11 +1219,21 @@ static void __init iort_init_platform_devices(void)
> acpi_free_fwnode_static(fwnode);
> return;
> }
> +
> + smmu_detected = true;
> }
>
> iort_node = ACPI_ADD_PTR(struct acpi_iort_node, iort_node,
> iort_node->length);
> }
> +
> + /*
> + * If IORT reports an SMMU component make sure PCI ACS is
> + * requested so that PCI devices can enable it in their
> + * capabilities.
> + */
> + if (smmu_detected)
> + pci_request_acs();
> }
>
> void __init acpi_iort_init(void)
>
Hi Lorenzo,
I tested this patch, it works well in my HiSilicon Hip08 based system.
However, setting ACS flag at the stage of SMMU device init seems not good,
I mean what if in one system there are only platform devices connected to
SMMU device.
Best,
Zhou
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