IOMMU_FWSPEC_PCI_RC_ATS for SMMUv3 with DT configuration?

IOMMU_FWSPEC_PCI_RC_ATS for SMMUv3 with DT configuration?

[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?

Thanks
Nicolin

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Re: 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


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Re: IOMMU_FWSPEC_PCI_RC_ATS for SMMUv3 with DT configuration?

[Nicolin Chen]

Hi Jean,

On Mon, Mar 04, 2024 at 09:25:36AM +0000, Jean-Philippe Brucker wrote:
> 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 for the reply and links!

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

Thank you
Nicolin

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Re: IOMMU_FWSPEC_PCI_RC_ATS for SMMUv3 with DT configuration?

[Nicolin Chen]

Hi Jean,

On Wed, Mar 06, 2024 at 07:53:20PM -0800, Nicolin Chen wrote:
> On Mon, Mar 04, 2024 at 09:25:36AM +0000, Jean-Philippe Brucker wrote:
> > > 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

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

My team mate verified this patch using a DT configuration.

Would it be possible for you to respin the of_iommu patch?

If yes, please also add his tag:
Tested-by: Ketan Patil <ketanp@nvidia.com>

Thanks!
Nicolin

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