Re: [PATCH v2 2/3] arm64: tegra: Add GPCDMA support for Tegra I2C

Thierry Reding
2022-10-07T13:20:47Z

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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
>
> 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(+)
>
> diff --git a/arch/arm64/boot/dts/nvidia/tegra186.dtsi b/arch/arm64/boot/dts/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 = "div-clk";
> resets = <&bpmp TEGRA186_RESET_I2C1>;
> reset-names = "i2c";
> + iommus = <&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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