Subject: Re: [PATCH RFC v6 1/6] dt-bindings: exynos-bus: Add documentation for interconnect properties

From: Rob Herring <[email-masked]>
Date: Thu, 9 Jul 2020 15:04:48 -0600

On Thu, Jul 02, 2020 at 06:37:19PM +0200, Sylwester Nawrocki wrote:
> Add documentation for new optional properties in the exynos bus nodes:
> samsung,interconnect-parent, #interconnect-cells, bus-width.
> These properties allow to specify the SoC interconnect structure which
> then allows the interconnect consumer devices to request specific
> bandwidth requirements.
> 
> Signed-off-by: Artur Świgoń <[email-masked]>
> Signed-off-by: Sylwester Nawrocki <[email-masked]>
> ---
> Changes for v6:
>  - added dts example of bus hierarchy definition and the interconnect
>    consumer,
>  - added new bus-width property.
> 
> Changes for v5:
>  - exynos,interconnect-parent-node renamed to samsung,interconnect-parent
> ---
>  .../devicetree/bindings/devfreq/exynos-bus.txt     | 68 +++++++++++++++++++++-
>  1 file changed, 66 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> index e71f752..4035e3e 100644
> --- a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> +++ b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> @@ -51,6 +51,13 @@ Optional properties only for parent bus device:
>  - exynos,saturation-ratio: the percentage value which is used to calibrate
>  			the performance count against total cycle count.
>  
> +Optional properties for interconnect functionality (QoS frequency constraints):
> +- samsung,interconnect-parent: phandle to the parent interconnect node; for
> +  passive devices should point to same node as the exynos,parent-bus property.

Adding vendor specific properties for a common binding defeats the 
point.

> +- #interconnect-cells: should be 0.
> +- bus-width: the interconnect bus width in bits, default value is 8 when this
> +  property is missing.

Your bus is 8-bits or 4-bits as the example?

> +
>  Detailed correlation between sub-blocks and power line according to Exynos SoC:
>  - In case of Exynos3250, there are two power line as following:
>  	VDD_MIF |--- DMC
> @@ -135,7 +142,7 @@ Detailed correlation between sub-blocks and power line according to Exynos SoC:
>  		|--- PERIC (Fixed clock rate)
>  		|--- FSYS  (Fixed clock rate)
>  
> -Example1:
> +Example 1:
>  	Show the AXI buses of Exynos3250 SoC. Exynos3250 divides the buses to
>  	power line (regulator). The MIF (Memory Interface) AXI bus is used to
>  	transfer data between DRAM and CPU and uses the VDD_MIF regulator.
> @@ -184,7 +191,7 @@ Example1:
>  	|L5   |200000 |200000  |400000 |300000 |       ||1000000 |
>  	----------------------------------------------------------
>  
> -Example2 :
> +Example 2:
>  	The bus of DMC (Dynamic Memory Controller) block in exynos3250.dtsi
>  	is listed below:
>  
> @@ -419,3 +426,60 @@ Example2 :
>  		devfreq = <&bus_leftbus>;
>  		status = "okay";
>  	};
> +
> +Example 3:
> +	An interconnect path "bus_display -- bus_leftbus -- bus_dmc" on
> +	Exynos4412 SoC with video mixer as an interconnect consumer device.
> +
> +	soc {
> +		bus_dmc: bus_dmc {
> +			compatible = "samsung,exynos-bus";
> +			clocks = <&clock CLK_DIV_DMC>;
> +			clock-names = "bus";
> +			operating-points-v2 = <&bus_dmc_opp_table>;
> +			bus-width = <4>;
> +			#interconnect-cells = <0>;
> +			status = "disabled";
> +		};
> +
> +		bus_leftbus: bus_leftbus {
> +			compatible = "samsung,exynos-bus";
> +			clocks = <&clock CLK_DIV_GDL>;
> +			clock-names = "bus";
> +			operating-points-v2 = <&bus_leftbus_opp_table>;
> +			samsung,interconnect-parent = <&bus_dmc>;
> +			#interconnect-cells = <0>;
> +			status = "disabled";
> +		};
> +
> +		bus_display: bus_display {
> +			compatible = "samsung,exynos-bus";
> +			clocks = <&clock CLK_ACLK160>;
> +			clock-names = "bus";
> +			operating-points-v2 = <&bus_display_opp_table>;
> +			samsung,interconnect-parent = <&bus_leftbus>;
> +			#interconnect-cells = <0>;
> +			status = "disabled";
> +		};
> +
> +		bus_dmc_opp_table: opp_table1 {
> +			compatible = "operating-points-v2";
> +			/* ... */
> +		}
> +
> +		bus_leftbus_opp_table: opp_table3 {
> +			compatible = "operating-points-v2";
> +			/* ... */
> +		};
> +
> +		bus_display_opp_table: opp_table4 {
> +			compatible = "operating-points-v2";
> +			/* .. */
> +		};
> +
> +		&mixer {
> +			compatible = "samsung,exynos4212-mixer";
> +			interconnects = <&bus_display &bus_dmc>;
> +			/* ... */
> +		};
> +	};
> -- 
> 2.7.4
> 

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