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

[Pranjal Shrivastava]

Hi Peng,

On Tue, Oct 15, 2024 at 11:14:41AM +0800, 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 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.

Any reason why you can't use the sysfs to change the iommu domain type?
i.e. by using the /sys/kernel/iommu_groups/<iommu_group_number>/type
AFAIK, the arm-smmu-v3 driver allocates one iommu_group per device.

> 
> 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,
> -- 
> Peng Fan <peng.fan@xxxxxxx>
> 
> 

Thanks,
Pranjal