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

[Marek Szyprowski]

Hi All,

On 2018-03-06 08:59, Geert Uytterhoeven wrote:
> Hi Rob, Jolly,
>
> On Mon, Mar 5, 2018 at 11:39 PM, Rob Herring <robh@xxxxxxxxxx> 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@xxxxxxxxxx>
> > > Signed-off-by: Rajan Vaja <rajanv@xxxxxxxxxx>
> > > ---
> > >   .../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?

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>;
> > > +             };
> > > +     };

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