Re: [PATCH 3/6] dt-bindings: iommu: Add Broadcom BCM2712 IOMMU

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The `brcm,bcm2712-iommu` binding unconditionally requires the `brcm,iommu-cache` property, breaking validation compatibility with existing RPi5 firmware.
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--- Patch [3]: [PATCH 3/6] dt-bindings: iommu: Add Broadcom BCM2712 IOMMU ---
commit abf846fdde20af5f8370795e68ffc7099b1c33db
Author: Daniel Drake <dan@reactivated.net>

dt-bindings: iommu: Add Broadcom BCM2712 IOMMU

This commit adds device tree bindings for the Broadcom BCM2712 IOMMU
and its shared TLB cache. It aims to support hardware address translation
while maintaining compatibility with existing Raspberry Pi 5 firmware.

> diff --git a/Documentation/devicetree/bindings/iommu/brcm,bcm2712-iommu.yaml b/Documentation/devicetree/bindings/iommu/brcm,bcm2712-iommu.yaml
> new file mode 100644
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iommu/brcm,bcm2712-iommu.yaml

[ ... ]

> +required:
> +  - compatible
> +  - reg
> +  - '#iommu-cells'
> +  - brcm,iommu-cache

[Severity: Medium]
Will this cause schema validation to fail for older device trees?

The commit message mentions including compatibility with the cache phandle
used in existing firmware shipped on Raspberry Pi 5. If those existing
device trees use the deprecated "cache" property instead of
"brcm,iommu-cache", unconditionally requiring "brcm,iommu-cache" here
seems like it would break dtbs_check validation for them.

Could this be handled using a oneOf rule to require either
"brcm,iommu-cache" or "cache" to ensure older firmware setups still pass
validation?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260712-bcm2712-iommu-submit-v1-0-80e10cdde2ea@reactivated.net?part=3