linux-kernel - Re: [PATCH v2 2/4] dt-bindings: Add TI SCI PM Domains

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Message-ID: <7heg39pmgb.fsf@baylibre.com>
Date:   Fri, 21 Oct 2016 11:48:52 -0700
From:   Kevin Hilman <khilman@...libre.com>
To:     Dave Gerlach <d-gerlach@...com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
        <devicetree@...r.kernel.org>, Nishanth Menon <nm@...com>,
        Keerthy <j-keerthy@...com>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Tero Kristo <t-kristo@...com>,
        Sudeep Holla <sudeep.holla@....com>,
        Santosh Shilimkar <ssantosh@...nel.org>
Subject: Re: [PATCH v2 2/4] dt-bindings: Add TI SCI PM Domains

Dave Gerlach <d-gerlach@...com> writes:

> Add a generic power domain implementation, TI SCI PM Domains, that
> will hook into the genpd framework and allow the TI SCI protocol to
> control device power states.
>
> Also, provide macros representing each device index as understood
> by TI SCI to be used in the device node power-domain references.
> These are identifiers for the K2G devices managed by the PMMC.
>
> Signed-off-by: Nishanth Menon <nm@...com>
> Signed-off-by: Dave Gerlach <d-gerlach@...com>
> ---
>  .../devicetree/bindings/soc/ti/sci-pm-domain.txt   | 54 +++++++++++++
>  MAINTAINERS                                        |  2 +
>  include/dt-bindings/genpd/k2g.h                    | 90 ++++++++++++++++++++++
>  3 files changed, 146 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/soc/ti/sci-pm-domain.txt
>  create mode 100644 include/dt-bindings/genpd/k2g.h
>
> diff --git a/Documentation/devicetree/bindings/soc/ti/sci-pm-domain.txt b/Documentation/devicetree/bindings/soc/ti/sci-pm-domain.txt
> new file mode 100644
> index 000000000000..32f38a349656
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/soc/ti/sci-pm-domain.txt
> @@ -0,0 +1,54 @@
> +Texas Instruments TI-SCI Generic Power Domain
> +---------------------------------------------
> +
> +Some TI SoCs contain a system controller (like the PMMC, etc...) that is
> +responsible for controlling the state of the IPs that are present.
> +Communication between the host processor running an OS and the system
> +controller happens through a protocol known as TI-SCI [1]. This pm domain
> +implementation plugs into the generic pm domain framework and makes use of
> +the TI SCI protocol power on and off each device when needed.
> +
> +[1] Documentation/devicetree/bindings/arm/keystone/ti,sci.txt
> +
> +PM Domain Node
> +==============
> +The PM domain node represents the global PM domain managed by the PMMC,
> +which in this case is the single implementation as documented by the generic
> +PM domain bindings in Documentation/devicetree/bindings/power/power_domain.txt.
> +
> +Required Properties:
> +--------------------
> +- compatible: should be "ti,sci-pm-domain"
> +- #power-domain-cells: Must be 0.
> +- ti,sci: Phandle to the TI SCI device to use for managing the devices.
>
> +Example:
> +--------------------
> +k2g_pds: k2g_pds {

should use generic name like "power-contoller", e.g. k2g_pds: power-controller

> +        compatible = "ti,sci-pm-domain";
> +        #power-domain-cells = <0>;
> +        ti,sci = <&pmmc>;
> +};
> +
> +PM Domain Consumers
> +===================
> +Hardware blocks that require SCI control over their state must provide
> +a reference to the sci-pm-domain they are part of and a unique device
> +specific ID that identifies the device.
> +
> +Required Properties:
> +--------------------
> +- power-domains: phandle pointing to the corresponding PM domain node.
> +- ti,sci-id: index representing the device id to be passed oevr SCI to
> +	     be used for device control.

This ID doesn't look right.

Why not use #power-domain-cells = <1> and pass the index in the DT? ...

> +See dt-bindings/genpd/k2g.h for the list of valid identifiers for k2g.
> +
> +Example:
> +--------------------
> +uart0: serial@...30c00 {
> +	compatible = "ns16550a";
> +	...
> +	power-domains = <&k2g_pds>;
> +	ti,sci-id = <K2G_DEV_UART0>;

... like this:

	power-domains = <&k2g_pds K2G_DEV_UART0>;

Kevin