linux-kernel - Re: [RFC PATCH v1 5/5] arm64: tegra: Add Tegra VI CSI suppport in device tree

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Date:   Wed, 29 Jan 2020 10:46:24 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>
Cc:     jonathanh@...dia.com, frankc@...dia.com, hverkuil@...all.nl,
        linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v1 5/5] arm64: tegra: Add Tegra VI CSI suppport in
 device tree

On Tue, Jan 28, 2020 at 10:23:21AM -0800, Sowjanya Komatineni wrote:
> Tegra210 contains VI controller for video input capture from MIPI
> CSI camera sensors and also supports built-in test pattern generator.
> 
> CSI ports can be one-to-one mapped to VI channels for capturing from
> an external sensor or from built-in test pattern generator.
> 
> This patch adds support for VI and CSI and enables them in Tegra210
> device tree.
> 
> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
> ---
>  arch/arm64/boot/dts/nvidia/tegra210-p2597.dtsi |  8 +++++++
>  arch/arm64/boot/dts/nvidia/tegra210.dtsi       | 31 +++++++++++++++++++++++++-
>  2 files changed, 38 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/boot/dts/nvidia/tegra210-p2597.dtsi b/arch/arm64/boot/dts/nvidia/tegra210-p2597.dtsi
> index b0095072bc28..ec1b3033fa03 100644
> --- a/arch/arm64/boot/dts/nvidia/tegra210-p2597.dtsi
> +++ b/arch/arm64/boot/dts/nvidia/tegra210-p2597.dtsi
> @@ -10,6 +10,14 @@
>  			status = "okay";
>  		};
>  
> +		vi@...80000 {
> +			status = "okay";
> +		};
> +
> +		csi@...4080838 {
> +			status = "okay";
> +		};
> +
>  		sor@...80000 {
>  			status = "okay";
>  
> diff --git a/arch/arm64/boot/dts/nvidia/tegra210.dtsi b/arch/arm64/boot/dts/nvidia/tegra210.dtsi
> index 48c63256ba7f..c6107ec03ad1 100644
> --- a/arch/arm64/boot/dts/nvidia/tegra210.dtsi
> +++ b/arch/arm64/boot/dts/nvidia/tegra210.dtsi
> @@ -136,9 +136,38 @@
>  
>  		vi@...80000 {
>  			compatible = "nvidia,tegra210-vi";
> -			reg = <0x0 0x54080000 0x0 0x00040000>;
> +			reg = <0x0 0x54080000 0x0 0x808>;
>  			interrupts = <GIC_SPI 69 IRQ_TYPE_LEVEL_HIGH>;
>  			status = "disabled";
> +			assigned-clocks = <&tegra_car TEGRA210_CLK_VI>;
> +			assigned-clock-parents = <&tegra_car TEGRA210_CLK_PLL_C4_OUT0>;
> +
> +			clocks = <&tegra_car TEGRA210_CLK_VI>;
> +			clock-names = "vi";
> +			resets = <&tegra_car 20>;
> +			reset-names = "vi";
> +		};
> +
> +		csi@...4080838 {
> +			compatible = "nvidia,tegra210-csi";
> +			reg = <0x0 0x54080838 0x0 0x2000>;
> +			status = "disabled";
> +			assigned-clocks = <&tegra_car TEGRA210_CLK_CILAB>,
> +					  <&tegra_car TEGRA210_CLK_CILCD>,
> +					  <&tegra_car TEGRA210_CLK_CILE>;
> +			assigned-clock-parents = <&tegra_car TEGRA210_CLK_PLL_P>,
> +						 <&tegra_car TEGRA210_CLK_PLL_P>,
> +						 <&tegra_car TEGRA210_CLK_PLL_P>;
> +			assigned-clock-rates = <102000000>,
> +					       <102000000>,
> +					       <102000000>;
> +
> +			clocks = <&tegra_car TEGRA210_CLK_CSI>,
> +				 <&tegra_car TEGRA210_CLK_CILAB>,
> +				 <&tegra_car TEGRA210_CLK_CILCD>,
> +				 <&tegra_car TEGRA210_CLK_CILE>;
> +			clock-names = "csi", "cilab", "cilcd", "cile";
> +
>  		};

Can this be a child of the vi node? Looking at the register ranges it
seems like these are actually a single IP block. If they have separate
blocks with clearly separate functionality, then it makes sense to have
CSI be a child node of VI, though it may also be okay to merge both and
have a single node with the driver doing all of the differentiation
between what's VI and what's CSI.

Looking at later chips, the split between VI and CSI is more explicit,
so having the split in DT for Tegra210 may make sense for consistency.

I know we've discussed this before, but for some reason I keep coming
back to this. I'll go through the other patches to see if I can get a
clearer picture of how this could all work together.

Thierry

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