Re: [PATCH RFC 0/2] iommu/arm-smmu-v3: bypass streamid zero on i.MX95

[Robin Murphy]

On 2024-10-15 4:14 am, Peng Fan (OSS) wrote:
> i.MX95 eDMA3 connects to DSU ACP, supporting dma coherent memory to
> memory operations. However TBU is in the path between eDMA3 and ACP,
> need to bypass the default SID 0 to make eDMA3 work properly.

I'm confused, why not just describe that the device owns this StreamID 
in the DT the normal way, i.e, "iommus = <&smmu 0>;"?

Thanks,
Robin.

> I was also thinking to introduce "bypass-sids = <0xA 0xB 0xC ...>" to
> make this reusable for others, but not sure. I could switch to
> "bypass-sids" if you prefer.
>
> Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
> ---
> Peng Fan (2):
>        dt-bindings: iommu: arm,smmu-v3: introduce nxp,imx95-bypass-sid-zero
>        iommu/arm-smmu-v3: Bypass SID0 for NXP i.MX95
>
>   .../devicetree/bindings/iommu/arm,smmu-v3.yaml        |  4 ++++
>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c           | 19 ++++++++++++++++---
>   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h           |  1 +
>   3 files changed, 21 insertions(+), 3 deletions(-)
> ---
> base-commit: d61a00525464bfc5fe92c6ad713350988e492b88
> change-id: 20241014-smmuv3-120b24bc4659
>
> Best regards,