IOMMU_FWSPEC_PCI_RC_ATS for SMMUv3 with DT configuration?

Hi all.

Currently, the SMMUv3 driver relies on IOMMU_FWSPEC_PCI_RC_ATS in arm_smmu_ats_supported(). This flag seems to be only set in the drivers/acpi/arm64/iort.c file, which does not work for DT configuration.

We have a need to enable ATS on a system using Device Tree. Is there a suggested way or name of DT binding to add?

Hi,

Quoted 9 lines · Nicolin Chen

Hi all.

Currently, the SMMUv3 driver relies on IOMMU_FWSPEC_PCI_RC_ATS in arm_smmu_ats_supported(). This flag seems to be only set in the drivers/acpi/arm64/iort.c file, which does not work for DT configuration.

We have a need to enable ATS on a system using Device Tree. Is there a suggested way or name of DT binding to add?

"ats-supported" was acked by Rob:

https://lore.kernel.org/linux-iommu/[email protected]/

I don't remember why I didn't follow up with that series, probably just the lack of users at the time (Arm SW model was the only ATS implementation). A simpler implementation would be setting the existing fwspec flag:
https://jpbrucker.net/git/linux/commit/?h=sva/current&id=4b6d187154557a7c46c9a67c13453d40a03cc078

Quoted 7 lines · Jean-Philippe Brucker

Quoted 2 lines

We have a need to enable ATS on a system using Device Tree. Is there a suggested way or name of DT binding to add?

"ats-supported" was acked by Rob:

https://lore.kernel.org/linux-iommu/[email protected]/

Quoted 5 lines

I don't remember why I didn't follow up with that series, probably just the lack of users at the time (Arm SW model was the only ATS implementation). A simpler implementation would be setting the existing fwspec flag:
https://jpbrucker.net/git/linux/commit/?h=sva/current&id=4b6d187154557a7c46c9a67c13453d40a03cc078

I am out of office this week. So I've asked my team mate to get that a try.