Re: [PATCH v2 22/22] arm64: dts: apple: t60xx: Add USB4 ACIO and NHI

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] The apple,dart nodes for USB4 in t602x-dieX.dtsi incorrectly specify `#iommu-cells = <5>`, which causes the apple-dart driver to reject the IOMMU configuration and breaks USB4 support on t602x hardware.
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commit 4665bd18e7a65a6f449efb387c1fa31def24848a
Author: Sven Peter <sven@kernel.org>

arm64: dts: apple: t60xx: Add USB4 ACIO and NHI

This commit adds the ACIO host router, NHI, DART, and mailbox nodes for the
ATC instances on t600x and t602x dies. It connects the host routers to the
Type-C connectors on several Apple Silicon boards and describes the USB3
paths.

> diff --git a/arch/arm64/boot/dts/apple/t602x-dieX.dtsi b/arch/arm64/boot/dts/apple/t602x-dieX.dtsi
> --- a/arch/arm64/boot/dts/apple/t602x-dieX.dtsi
> +++ b/arch/arm64/boot/dts/apple/t602x-dieX.dtsi
[ ... ]
> @@ -133,6 +149,96 @@ DIE_NODE(pmgr_gfx): power-management@404e80000 {
[ ... ]
> +		DIE_NODE(usb4_0_dart): iommu@a80000 {
> +			compatible = "apple,t6020-dart", "apple,t8110-dart";
> +			reg = <0xa80000 0x4000>;
> +			interrupt-parent = <&aic>;
> +			interrupts = <AIC_IRQ DIE_NO 1387 IRQ_TYPE_LEVEL_HIGH>;
> +			#iommu-cells = <5>;
> +		};
> +
> +		DIE_NODE(usb4_0_nhi): nhi@f00000 {
[ ... ]
> +			iommus = <&DIE_NODE(usb4_0_dart) 1 0x100 0x0 0x10 0x0>,
> +				 <&DIE_NODE(usb4_0_dart) 2 0x100 0x0 0x10 0x0>;

[Severity: High]
Does this correctly configure the IOMMU for the USB4 controller?

The apple_dart_of_xlate() function in drivers/iommu/apple-dart.c explicitly
enforces args->args_count == 1 and returns -EINVAL otherwise. Specifying
#iommu-cells = <5> for the usb4_0_dart node and passing 5 arguments in the
iommus property for usb4_0_nhi will cause an unconditional failure to set
up the IOMMU for the USB4 controller.

Will this cause the IOMMU subsystem to reject the configuration during probe
and leave the USB4 controller unusable on t602x hardware?

> +			/* To be filled by the loader */
> +			apple,thunderbolt-drom = [00];
> +		};
> +	};

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260906-b4-apple-soc-tbt-v2-0-1f80085f93fb@kernel.org?part=22