Re: [PATCH v2 1/4] dt-bindings: iommu: arm,smmu-v3: Allow a clock and a reset

From: Sebastian Reichel <sebastian.reichel@collabora.com>
To: aiyengar1990@gmail.com
Cc: Will Deacon <will@kernel.org>,
	Robin Murphy <robin.murphy@arm.com>,
	 "Joerg Roedel (AMD)" <joro@8bytes.org>,
	Rob Herring <robh@kernel.org>,
	 Krzysztof Kozlowski <krzk+dt@kernel.org>,
	Conor Dooley <conor+dt@kernel.org>,
	 Heiko Stuebner <heiko@sntech.de>,
	Niklas Cassel <cassel@kernel.org>,
	 Pranjal Shrivastava <praan@google.com>,
	linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
	 linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
	linux-rockchip@lists.infradead.org,
	 Shawn Lin <shawn.lin@rock-chips.com>,
	Simon Xue <xxm@rock-chips.com>,
	 Finley Xiao <finley.xiao@rock-chips.com>
Subject: Re: [PATCH v2 1/4] dt-bindings: iommu: arm,smmu-v3: Allow a clock and a reset
Date: Thu, 12 Nov 2026 17:38:01 +0100	[thread overview]
Message-ID: <avXqeBBO_osbgdgU@venus> (raw)
In-Reply-To: <20261112-smmu-v3-pcie-pd-v2-1-3a77bbb6b2c4@gmail.com>

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Hi,

On Thu, Nov 12, 2026 at 08:20:22AM +0000, Arun Iyengar via B4 Relay wrote:
> From: Arun Iyengar <aiyengar1990@gmail.com>
> 
> Some SoCs feed the SMMUv3 from a clock that the OS controls. On the
> Rockchip RK3588 the MMU-600 for PCIe runs from ACLK_MMU_PCIE, whose only
> other consumers are the PCIe controllers. When no PCIe controller is
> enabled, the clock framework gates it as unused, and the SMMU can no
> longer be accessed. The same SMMU also has a reset line in the CRU,
> SRST_A_MMU_PCIE.
> 
> Allow a single clock and a single reset, so that both can be described.
> The architecture defines no clock or reset inputs; the MMU-600 TRM lists
> one clock and one reset signal, and the one integration that needs this
> has one of each. An implementation with more clocks or resets can add
> them with names and a specific compatible.

You can trim that down quite a bit. Don't take over AI text 1:1.

> 
> Link: https://support.arm.com/documentation/100310/0202/Signal-descriptions/Clock-and-reset-signals
> Signed-off-by: Arun Iyengar <aiyengar1990@gmail.com>
> ---
>  Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml
> index 3c044e4f03d4..29b81b4fb650 100644
> --- a/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml
> +++ b/Documentation/devicetree/bindings/iommu/arm,smmu-v3.yaml
> @@ -63,6 +63,17 @@ properties:
>  
>    msi-parent: true
>  
> +  clocks:
> +    maxItems: 1
> +    description:
> +      Clock of the SMMU's register and memory interfaces, on SoCs where the
> +      OS has to keep it running.
> +
> +  resets:
> +    maxItems: 1
> +    description:
> +      Reset of the SMMU, on SoCs where it is controlled by the OS.

The ', on SoCs where it is controlled by the OS.' is completley
useless for both. You need to review your AI output and not take
it over without doing any thinking yourself.

Greetings,

-- Sebastian

>    nvidia,cmdqv:
>      description: |
>        A phandle to its pairing CMDQV extension for an implementation on NVIDIA
> 

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