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Date:   Fri, 7 Oct 2022 15:20:37 +0200
From:   Thierry Reding <thierry.reding@gmail.com>
To:     Akhil R <akhilrajeev@nvidia.com>
Cc:     christian.koenig@amd.com, devicetree@vger.kernel.org,
        digetx@gmail.com, jonathanh@nvidia.com, ldewangan@nvidia.com,
        linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-tegra@vger.kernel.org, robh+dt@kernel.org,
        sumit.semwal@linaro.org, wsa@kernel.org
Subject: Re: [PATCH v2 2/3] arm64: tegra: Add GPCDMA support for Tegra I2C
Message-ID: <Y0AnpYeECoyQchmY@orome>
References: <20220906144716.16274-1-akhilrajeev@nvidia.com>
 <20220906144716.16274-3-akhilrajeev@nvidia.com>
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On Tue, Sep 06, 2022 at 08:17:15PM +0530, Akhil R wrote:
> Add dma properties to support GPCDMA for I2C in Tegra 186 and later
> chips
>=20
> Signed-off-by: Akhil R <akhilrajeev@nvidia.com>
> ---
>  arch/arm64/boot/dts/nvidia/tegra186.dtsi | 32 ++++++++++++++++++++++++
>  arch/arm64/boot/dts/nvidia/tegra194.dtsi | 32 ++++++++++++++++++++++++
>  arch/arm64/boot/dts/nvidia/tegra234.dtsi | 32 ++++++++++++++++++++++++
>  3 files changed, 96 insertions(+)
>=20
> diff --git a/arch/arm64/boot/dts/nvidia/tegra186.dtsi b/arch/arm64/boot/d=
ts/nvidia/tegra186.dtsi
> index 59a10fb184f8..3580fbf99091 100644
> --- a/arch/arm64/boot/dts/nvidia/tegra186.dtsi
> +++ b/arch/arm64/boot/dts/nvidia/tegra186.dtsi
> @@ -672,6 +672,10 @@
>  		clock-names =3D "div-clk";
>  		resets =3D <&bpmp TEGRA186_RESET_I2C1>;
>  		reset-names =3D "i2c";
> +		iommus =3D <&smmu TEGRA186_SID_GPCDMA_0>;
> +		dma-coherent;

I wonder: why do we need the iommus and dma-coherent properties here?
The I2C controllers are not directly accessing memory, instead it's the
GPCDMA via the dmas/dma-names properties. The GPCDMA already has these
properties set, so they seem to be useless here.

I'm asking because they cause a lot of warnings from the DT validators,
so we either need to remove them (if they are not necessary) or add the
DT binding documentation for them.

Thierry

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