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

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Message-ID: <Zw4drtlAGy-LW7Ov@google.com>
Date: Tue, 15 Oct 2024 07:45:50 +0000
From: Pranjal Shrivastava <praan@...gle.com>
To: "Peng Fan (OSS)" <peng.fan@....nxp.com>
Cc: Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
	Joerg Roedel <joro@...tes.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, Joy Zou <joy.zou@....com>,
	linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	Peng Fan <peng.fan@....com>, Jason Gunthorpe <jgg@...pe.ca>
Subject: Re: [PATCH RFC 0/2] iommu/arm-smmu-v3: bypass streamid zero on i.MX95

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@....com>
> ---
> 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@....com>
> 
> 

Thanks,
Pranjal