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

Lv Zheng
2026-02-06T01:33:55Z

On 2/6/2026 2:24 AM, Conor Dooley wrote:
> 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.

SpacemiT provides RISC-V IOMMU implementation, T100 is the first
generation of the this IP product line, we have plan to develop T200,
T300, etc., with more features introduced to be adoptive to new
RISC-V IOMMU specifications.
Besides, T100 is not only shipped in K3, but also shipped in V100 and
the follow-up SoCs, like Kn, Vn00, they will likely use the same
synthesis result of T100 RTLs.

From SpacemiT's point of view, we need a common sense of this IP
series for something like IOATCs, that's why spacemit,riscv-iommu
(this is same like qemu,riscv-iommu) is introduced. And a common sense
of T100 for all SoCs shipped T100 (like global filters, vendor events
and etc.,).

IMO, the current compatible is proper to reflect these concerns.
What do you think?

Cheers,
Lv

>
> Cheers,
> Conor.