linux-kernel - Re: [PATCH 1/2] dt-bindings: power: Add ZynqMP power domain bindings

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Date:   Fri, 18 May 2018 08:30:45 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Jolly Shah <JOLLYS@...inx.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Rob Herring <robh@...nel.org>
Cc:     Matthias Brugger <matthias.bgg@...il.com>,
        Andy Gross <andy.gross@...aro.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Björn Andersson <bjorn.andersson@...aro.org>,
        "sean.wang@...iatek.com" <sean.wang@...iatek.com>,
        Michal Simek <michal.simek@...inx.com>,
        Mark Rutland <mark.rutland@....com>,
        Rajan Vaja <RAJANV@...inx.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] dt-bindings: power: Add ZynqMP power domain
 bindings

Hi Jolly,

On 2018-05-17 23:10, Jolly Shah wrote:

>>>>>> +Example:
>>>>>> +     zynqmp-genpd {
>>>>>> +             compatible = "xlnx,zynqmp-genpd";
>>>>> What's the control interface for controlling the domains?
>>>>>> +
>>>>>> +             pd_usb0: pd-usb0 {
>>>>>> +                     pd-id = <22>;
>>>>>> +                     #power-domain-cells = <0>;
>>>>> There's no need for all these sub nodes. Make #power-domain-cells 1
>>>>> and put the id in the cell value.
>>>> That was my first reaction, too...
>>>>>> +             };
>>>>>> +
>>>>>> +             pd_sata: pd-sata {
>>>>>> +                     pd-id = <28>;
>>>>>> +                     #power-domain-cells = <0>;
>>>>>> +             };
>>>>>> +
>>>>>> +             pd_gpu: pd-gpu {
>>>>>> +                     pd-id = <58 20 21>;
>>>> ... until I saw the above.
>>>> Controlling the GPU power area requires controlling 3 physical areas?
>>>>
>>>> However, doing it this way may bite you in the future, if a need
>>>> arises to control a subset. And what about power up/down order?
>>> What about defining 3 separate domains and arranging them in
>>> parent-child relationship? generic power domains already supports that
>>> and this allows to nicely define the power on/off order.
>>>
>>>>>> +                     #power-domain-cells = <0x0>;
>>>>>> +             };
>>>>>> +     };
>> I agree it should be arranged in as parent child order to control subset or control
>> order. Will incorporate those changes in next version.
>
> As suggested, I tried out parent, child approach. However what I found is Genpd core takes care of parent child dependencies for power on off routines only. In our case, We need them in attach-detach routines too. In that case, we need to handle dependencies manually for those routines. Please suggest better approach, if any.

What do you mean to handle attach-detach?

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland