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Message-ID: <CAL_JsqJenHAOw4gApzGpuj-8nZjkYhmBg0qBj-DV+CEJ7zXuVw@mail.gmail.com>
Date: Tue, 5 Oct 2021 19:58:24 -0500
From: Rob Herring <robh+dt@...nel.org>
To: Hector Martin <marcan@...can.st>
Cc: linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
Marc Zyngier <maz@...nel.org>, Arnd Bergmann <arnd@...nel.org>,
Linus Walleij <linus.walleij@...aro.org>,
Alyssa Rosenzweig <alyssa@...enzweig.io>,
Krzysztof Kozlowski <krzk@...nel.org>,
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,
"open list:THERMAL" <linux-pm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
"open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>
Subject: Re: [PATCH 2/7] dt-bindings: power: Add apple,pmgr-pwrstate binding
On Tue, Oct 5, 2021 at 10:59 AM Hector Martin <marcan@...can.st> 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".
Is that because past SoCs used the same registers? I don't see how
else you have any insight to what future SoCs will do.
Normally we don't do 1 node per register type bindings, so I'm a bit
leery about doing 1 node per domain.
>
> 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.
> +
> +properties:
> + $nodename:
> + pattern: "^power-controller@[0-9a-f]+$"
Drop this and define this node in the syscon schema with a $ref to this schema.
> +
> + 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.
> +
> + apple,domain-name:
> + 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
No other power domain binding needs this, why do you?
> +
> + 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
> +
> +examples:
I prefer 1 complete example in the MFD schema rather than piecemeal examples.
> + - |
> + soc {
> + #address-cells = <2>;
> + #size-cells = <2>;
> +
> + power-management@...700000 {
> + compatible = "apple,t8103-pmgr", "apple,pmgr", "syscon", "simple-mfd";
> + #address-cells = <1>;
> + #size-cells = <0>;
As the child nodes are memory mapped devices, size should be 1. Then
address translation works (though Linux doesn't care (currently)).
> + reg = <0x2 0x3b700000 0x0 0x14000>;
> +
> + ps_sio: power-controller@1c0 {
> + compatible = "apple,t8103-pmgr-pwrstate", "apple,pmgr-pwrstate";
> + reg = <0x1c0>;
> + #power-domain-cells = <0>;
> + #reset-cells = <0>;
> + apple,domain-name = "sio";
> + apple,always-on;
> + };
> +
> + ps_uart_p: power-controller@220 {
> + compatible = "apple,t8103-pmgr-pwrstate", "apple,pmgr-pwrstate";
> + reg = <0x220>;
> + #power-domain-cells = <0>;
> + #reset-cells = <0>;
> + apple,domain-name = "uart_p";
> + power-domains = <&ps_sio>;
> + };
> +
> + ps_uart0: power-controller@270 {
> + compatible = "apple,t8103-pmgr-pwrstate", "apple,pmgr-pwrstate";
> + reg = <0x270>;
> + #power-domain-cells = <0>;
> + #reset-cells = <0>;
> + apple,domain-name = "uart0";
> + power-domains = <&ps_uart_p>;
> + };
> + };
> + };
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d25598842d15..5fe53d9a2956 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1722,6 +1722,7 @@ F: Documentation/devicetree/bindings/arm/apple.yaml
> F: Documentation/devicetree/bindings/arm/apple/*
> F: Documentation/devicetree/bindings/interrupt-controller/apple,aic.yaml
> F: Documentation/devicetree/bindings/pinctrl/apple,pinctrl.yaml
> +F: Documentation/devicetree/bindings/power/apple*
> F: arch/arm64/boot/dts/apple/
> F: drivers/irqchip/irq-apple-aic.c
> F: include/dt-bindings/interrupt-controller/apple-aic.h
> --
> 2.33.0
>
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