IOMMU_FWSPEC_PCI_RC_ATS for SMMUv3 with DT configuration?

[Jean-Philippe Brucker]

Hi,

On Fri, Mar 01, 2024 at 02:00:08PM -0800, Nicolin Chen wrote:
> 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/20200311124506.208376-2-jean-philippe@linaro.org/

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

Thanks,
Jean