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

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Date:   Tue, 6 Mar 2018 08:59:50 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Jolly Shah <jolly.shah@...inx.com>,
        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,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Michal Simek <michal.simek@...inx.com>,
        Mark Rutland <mark.rutland@....com>, 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>,
        Jolly Shah <jollys@...inx.com>
Subject: Re: [PATCH 1/2] dt-bindings: power: Add ZynqMP power domain bindings

Hi Rob, Jolly,

On Mon, Mar 5, 2018 at 11:39 PM, Rob Herring <robh@...nel.org> wrote:
> On Tue, Feb 27, 2018 at 03:55:49PM -0800, Jolly Shah wrote:
>> Add documentation to describe ZynqMP power domain bindings.
>>
>> Signed-off-by: Jolly Shah <jollys@...inx.com>
>> Signed-off-by: Rajan Vaja <rajanv@...inx.com>
>> ---
>>  .../devicetree/bindings/power/zynqmp-genpd.txt     | 46 ++++++++++++++++++++++
>>  1 file changed, 46 insertions(+)
>>  create mode 100644 Documentation/devicetree/bindings/power/zynqmp-genpd.txt
>>
>> diff --git a/Documentation/devicetree/bindings/power/zynqmp-genpd.txt b/Documentation/devicetree/bindings/power/zynqmp-genpd.txt
>> new file mode 100644
>> index 0000000..25f9711
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/power/zynqmp-genpd.txt

>> +This node contains a number of subnodes, each representing a single PM domain
>> +that PM domain consumer devices reference.
>> +
>> +== PM Domain Nodes ==
>> +
>> +Required properties:
>> + - #power-domain-cells: Number of cells in a PM domain specifier. Must be 0.
>> + - pd-id: List of domain identifiers of as defined by platform firmware. These
>> +       identifiers are passed to the PM firmware.
>> +
>> +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?

>> +                     #power-domain-cells = <0x0>;
>> +             };
>> +     };

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds