linux-kernel - Re: [RFC PATCH v5 1/6] dt-bindings: exynos-bus: Add documentation for interconnect properties

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Date:   Sun, 31 May 2020 09:01:00 +0900
From:   Chanwoo Choi <chanwoo@...nel.org>
To:     Sylwester Nawrocki <s.nawrocki@...sung.com>
Cc:     Georgi Djakov <georgi.djakov@...aro.org>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Artur Świgoń <a.swigon@...sung.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>, inki.dae@...sung.com,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH v5 1/6] dt-bindings: exynos-bus: Add documentation for
 interconnect properties

Hi Sylwester,


On Sat, May 30, 2020 at 1:32 AM Sylwester Nawrocki
<s.nawrocki@...sung.com> wrote:
>
> Add documentation for new optional properties in the exynos bus nodes:
> samsung,interconnect-parent, #interconnect-cells.
> 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 <a.swigon@...sung.com>
> Signed-off-by: Sylwester Nawrocki <s.nawrocki@...sung.com>
> ---
> Changes for v5:
>  - exynos,interconnect-parent-node renamed to samsung,interconnect-parent
> ---
>  Documentation/devicetree/bindings/devfreq/exynos-bus.txt | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> index e71f752..e0d2daa 100644
> --- a/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> +++ b/Documentation/devicetree/bindings/devfreq/exynos-bus.txt
> @@ -51,6 +51,11 @@ 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.
> +- #interconnect-cells: should be 0
> +
>  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
> @@ -185,8 +190,9 @@ Example1:
>         ----------------------------------------------------------
>
>  Example2 :
> -       The bus of DMC (Dynamic Memory Controller) block in exynos3250.dtsi
> -       is listed below:
> +       The bus of DMC (Dynamic Memory Controller) block in exynos3250.dtsi is
> +       listed below. An interconnect path "bus_lcd0 -- bus_leftbus -- bus_dmc"
> +       is defined for demonstration purposes.
>
>         bus_dmc: bus_dmc {
>                 compatible = "samsung,exynos-bus";
> @@ -376,12 +382,15 @@ Example2 :
>         &bus_dmc {
>                 devfreq-events = <&ppmu_dmc0_3>, <&ppmu_dmc1_3>;
>                 vdd-supply = <&buck1_reg>;      /* VDD_MIF */
> +               #interconnect-cells = <0>;
>                 status = "okay";
>         };
>
>         &bus_leftbus {
>                 devfreq-events = <&ppmu_leftbus_3>, <&ppmu_rightbus_3>;
>                 vdd-supply = <&buck3_reg>;
> +               samsung,interconnect-parent = <&bus_dmc>;
> +               #interconnect-cells = <0>;
>                 status = "okay";
>         };
>
> @@ -392,6 +401,8 @@ Example2 :
>
>         &bus_lcd0 {
>                 devfreq = <&bus_leftbus>;
> +               samsung,interconnect-parent = <&bus_leftbus>;
> +               #interconnect-cells = <0>;
>                 status = "okay";
>         };
>
> --
> 2.7.4
>

If you add the usage example like the mixer device of patch5 to this
dt-binding document,
I think it is very beneficial and more helpful for user of
exynos-bus/exynos-generic-icc.

Acked-by: Chanwoo Choi <cw00.choi@...sung.com>

--
Best Regards,
Chanwoo Choi
Samsung Electronics