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

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Message-ID: <03bcd54f-d5de-1a09-f487-1f6f165c0b34@samsung.com>
Date:   Mon, 1 Jun 2020 11:40:33 +0200
From:   Sylwester Nawrocki <s.nawrocki@...sung.com>
To:     Chanwoo Choi <chanwoo@...nel.org>
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>,
        Rob Herring <robh+dt@...nel.org>,
        devicetree <devicetree@...r.kernel.org>
Subject: Re: [RFC PATCH v5 1/6] dt-bindings: exynos-bus: Add documentation
 for interconnect properties

Hi Chanwoo,

On 31.05.2020 02:01, Chanwoo Choi wrote:
> 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>

Thanks for review. I will make sure the example includes a consumer
in next version. Will also mention ../interconnect/interconnect.txt
in description of the #interconnect-cells property.

-- 
Regards,
Sylwester