linux-kernel - Re: [PATCH 2/7] dt-bindings: power: Add apple,pmgr-pwrstate binding

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Date:   Wed, 6 Oct 2021 09:05:37 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
To:     Hector Martin <marcan@...can.st>,
        linux-arm-kernel@...ts.infradead.org
Cc:     Marc Zyngier <maz@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Arnd Bergmann <arnd@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mark Kettenis <mark.kettenis@...all.nl>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        devicetree@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-serial@...r.kernel.org
Subject: Re: [PATCH 2/7] dt-bindings: power: Add apple,pmgr-pwrstate binding

On 05/10/2021 17:59, Hector Martin wrote:
> This syscon child node represents a single SoC device controlled by the
> PMGR block. This layout allows us to declare all device power state
> controls (power/clock gating and reset) in the device tree, including
> dependencies, instead of hardcoding it into the driver. The register
> layout is uniform.
> 
> Each pmgr-pwrstate node provides genpd and reset features, to be
> consumed by downstream device nodes.
> 
> Future SoCs are expected to use backwards compatible registers, and the
> "apple,pmgr-pwrstate" represents any such interfaces (possibly with
> additional features gated by the more specific compatible), allowing
> them to be bound without driver updates. If a backwards incompatible
> change is introduced in future SoCs, it will require a new compatible,
> such as "apple,pmgr-pwrstate-v2".
> 
> Signed-off-by: Hector Martin <marcan@...can.st>
> ---
>  .../bindings/power/apple,pmgr-pwrstate.yaml   | 117 ++++++++++++++++++
>  MAINTAINERS                                   |   1 +
>  2 files changed, 118 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/power/apple,pmgr-pwrstate.yaml
> 
> diff --git a/Documentation/devicetree/bindings/power/apple,pmgr-pwrstate.yaml b/Documentation/devicetree/bindings/power/apple,pmgr-pwrstate.yaml
> new file mode 100644
> index 000000000000..a14bf5f30ff0
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/power/apple,pmgr-pwrstate.yaml
> @@ -0,0 +1,117 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/power/apple,pmgr-pwrstate.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Apple SoC PMGR Power States
> +
> +maintainers:
> +  - Hector Martin <marcan@...can.st>
> +
> +allOf:
> +  - $ref: "power-domain.yaml#"
> +
> +description: |
> +  Apple SoCs include a PMGR block responsible for power management,
> +  which can control various clocks, resets, power states, and
> +  performance features. This binding describes the device power
> +  state registers, which control power states and resets.
> +
> +  Each instance of a power controller within the PMGR syscon node
> +  represents a generic power domain provider, as documented in
> +  Documentation/devicetree/bindings/power/power-domain.yaml.
> +  The provider controls a single SoC block. The power hierarchy is
> +  represented via power-domains relationships between these nodes.
> +
> +  See Documentation/devicetree/bindings/arm/apple/apple,pmgr.yaml
> +  for the top-level PMGR node documentation.
> +
> +  IP cores belonging to a power domain should contain a
> +  "power-domains" property that is a phandle for the
> +  power domain node representing the domain.

Skip this last paragraph - it is obvious in usage of power domains.
Specific bindings should not duplicate generic knowledge.

> +
> +properties:
> +  $nodename:
> +    pattern: "^power-controller@[0-9a-f]+$"

Usually we call nodes as power-domain.

> +
> +  compatible:
> +    items:
> +      - enum:
> +          - apple,t8103-pmgr-pwrstate
> +      - const: apple,pmgr-pwrstate
> +
> +  reg:
> +    maxItems: 1
> +
> +  "#power-domain-cells":
> +    const: 0
> +
> +  "#reset-cells":
> +    const: 0
> +
> +  power-domains:
> +    description:
> +      Reference to parent power domains. A domain may have multiple parents,
> +      and all will be powered up when it is powered.

How many items?

> +
> +  apple,domain-name:

Use existing binding "label".

> +    description: |
> +      Specifies the name of the SoC device being controlled. This is used to
> +      name the power/reset domains.
> +    $ref: /schemas/types.yaml#/definitions/string
> +
> +  apple,always-on:
> +    description: |
> +      Forces this power domain to always be powered up.
> +    type: boolean
> +
> +required:
> +  - compatible
> +  - reg
> +  - "#power-domain-cells"
> +  - "#reset-cells"
> +  - "apple,domain-name"
> +
> +additionalProperties: false

Your parent schema should include this one for evaluating children.



Best regards,
Krzysztof