Re: [PATCH v3 4/8] dt-bindings: iommu: Add spacemit/t100 features

[Conor Dooley <conor@kernel.org>]

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On Thu, Feb 05, 2026 at 11:11:51AM +0800, Lv Zheng wrote:
> On 2/5/2026 1:37 AM, Conor Dooley wrote:
> > On Wed, Feb 04, 2026 at 05:09:12PM +0800, Lv Zheng wrote:
> > > Adds device tree bindings for SpacemiT T100 specific features by
> > > introducing spacemit,100 compatible. T100 contains distributed IOATCs,
> > > each of which exposes pmiv interrupt.
> > > 
> > > Signed-off-by: Lv Zheng <lv.zheng@linux.spacemit.com>
> > > Signed-off-by: Jingyu Li <joey.li@spacemit.com>
> > > ---
> > >   .../bindings/iommu/riscv,iommu.yaml           | 37 +++++++++++++++++++
> > >   1 file changed, 37 insertions(+)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/iommu/riscv,iommu.yaml b/Documentation/devicetree/bindings/iommu/riscv,iommu.yaml
> > > index d4838c3b3741..2da3456e7402 100644
> > > --- a/Documentation/devicetree/bindings/iommu/riscv,iommu.yaml
> > > +++ b/Documentation/devicetree/bindings/iommu/riscv,iommu.yaml
> > > @@ -32,6 +32,12 @@ properties:
> > >     # should be specified along with 'reg' property providing MMIO location.
> > >     compatible:
> > >       oneOf:
> > > +      - description: SpacemiT distributed IOMMUs
> > > +        items:
> > > +          - enum:
> > > +              - spacemit,t100
> > > +          - const: spacemit,riscv-iommu
> > 
> > What actually is the t100? Is it an SoC or is it the name of the core
> > complex IP that spacemit is using in multiple SoCs?
> 
> T100 is the name of the IOMMU IP developed by SpacemiT, announced in RISC-V
> 2024 China Summit:
> https://www.bilibili.com/video/BV1DNtCeiEBk/
> It's world first server SPEC IOMMU in RISC-V, supports IOTLB placed in
> adjacent to the DMA masters and supports PCIe ATS and PRI.
> You can find it shipped in the recent publicly purchasable SoC SpacemiT K3.

Right, then what you need here is something like:

items:
  - enum:
      - spacemit,k3-iommu
  - spacemit,t100-iommu
  - riscv,iommu

Driver can then match on spacemit,t100-iommu - but you need to have
soc-specific compatibles.
I'm not convinced that riscv,iommu is suitable here though, does the
driver work on your platform without the portions of code that are added
by this series and enabled by your new compatible? If not, the I don't
think the riscv,iommu fallback should be here.

Additionally, please stop sending new versions so frequently and in
response to earlier submissions. I have a v4 in my inbox while we are
still discussing v3.

Cheers,
Conor.

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