Subject: Re: [PATCH] dt-bindings: Add syscon YAML description

From: Rob Herring <[email-masked]>
Date: Tue, 5 Nov 2019 22:30:53 -0600

On Fri, Nov 01, 2019 at 03:10:34PM +0100, Maxime Ripard wrote:
> The syscon binding is a pretty loose one, with everyone having a bunch of
> vendor specific compatibles.
> 
> In order to start the effort to describe them using YAML, let's create a
> binding that tolerates additional, not listed, compatibles.
> 
> Signed-off-by: Maxime Ripard <[email-masked]>
> ---
>  .../devicetree/bindings/mfd/syscon.txt        | 32 --------
>  .../bindings/misc/allwinner,syscon.txt        | 20 -----
>  .../devicetree/bindings/misc/syscon.yaml      | 74 +++++++++++++++++++
>  3 files changed, 74 insertions(+), 52 deletions(-)
>  delete mode 100644 Documentation/devicetree/bindings/mfd/syscon.txt
>  delete mode 100644 Documentation/devicetree/bindings/misc/allwinner,syscon.txt
>  create mode 100644 Documentation/devicetree/bindings/misc/syscon.yaml
> 
> diff --git a/Documentation/devicetree/bindings/mfd/syscon.txt b/Documentation/devicetree/bindings/mfd/syscon.txt
> deleted file mode 100644
> index 25d9e9c2fd53..000000000000
> --- a/Documentation/devicetree/bindings/mfd/syscon.txt
> +++ /dev/null
> @@ -1,32 +0,0 @@
> -* System Controller Registers R/W driver
> -
> -System controller node represents a register region containing a set
> -of miscellaneous registers. The registers are not cohesive enough to
> -represent as any specific type of device. The typical use-case is for
> -some other node's driver, or platform-specific code, to acquire a
> -reference to the syscon node (e.g. by phandle, node path, or search
> -using a specific compatible value), interrogate the node (or associated
> -OS driver) to determine the location of the registers, and access the
> -registers directly.
> -
> -Required properties:
> -- compatible: Should contain "syscon".
> -- reg: the register region can be accessed from syscon
> -
> -Optional property:
> -- reg-io-width: the size (in bytes) of the IO accesses that should be
> -  performed on the device.
> -- hwlocks: reference to a phandle of a hardware spinlock provider node.
> -
> -Examples:
> -gpr: iomuxc-gpr@20e0000 {
> -	compatible = "fsl,imx6q-iomuxc-gpr", "syscon";
> -	reg = <0x020e0000 0x38>;
> -	hwlocks = <&hwlock1 1>;
> -};
> -
> -hwlock1: hwspinlock@40500000 {
> -	...
> -	reg = <0x40500000 0x1000>;
> -	#hwlock-cells = <1>;
> -};
> diff --git a/Documentation/devicetree/bindings/misc/allwinner,syscon.txt b/Documentation/devicetree/bindings/misc/allwinner,syscon.txt
> deleted file mode 100644
> index 31494a24fe69..000000000000
> --- a/Documentation/devicetree/bindings/misc/allwinner,syscon.txt
> +++ /dev/null
> @@ -1,20 +0,0 @@
> -* Allwinner sun8i system controller
> -
> -This file describes the bindings for the system controller present in
> -Allwinner SoC H3, A83T and A64.
> -The principal function of this syscon is to control EMAC PHY choice and
> -config.
> -
> -Required properties for the system controller:
> -- reg: address and length of the register for the device.
> -- compatible: should be "syscon" and one of the following string:
> -		"allwinner,sun8i-h3-system-controller"
> -		"allwinner,sun8i-v3s-system-controller"
> -		"allwinner,sun50i-a64-system-controller"
> -		"allwinner,sun8i-a83t-system-controller"
> -
> -Example:
> -syscon: syscon@1c00000 {
> -	compatible = "allwinner,sun8i-h3-system-controller", "syscon";
> -	reg = <0x01c00000 0x1000>;
> -};
> diff --git a/Documentation/devicetree/bindings/misc/syscon.yaml b/Documentation/devicetree/bindings/misc/syscon.yaml
> new file mode 100644
> index 000000000000..f2d81bed612f
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/misc/syscon.yaml
> @@ -0,0 +1,74 @@
> +# SPDX-License-Identifier: GPL-2.0
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/misc/syscon.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: System Controller Registers R/W Device Tree Bindings
> +
> +description: |
> +  System controller node represents a register region containing a set
> +  of miscellaneous registers. The registers are not cohesive enough to
> +  represent as any specific type of device. The typical use-case is
> +  for some other node's driver, or platform-specific code, to acquire
> +  a reference to the syscon node (e.g. by phandle, node path, or
> +  search using a specific compatible value), interrogate the node (or
> +  associated OS driver) to determine the location of the registers,
> +  and access the registers directly.
> +
> +maintainers:
> +  - Lee Jones <[email-masked]>
> +
> +properties:
> +  compatible:
> +    anyOf:
> +      - items:
> +        - enum:
> +          - allwinner,sun8i-a83t-system-controller
> +          - allwinner,sun8i-h3-system-controller
> +          - allwinner,sun8i-v3s-system-controller
> +          - allwinner,sun50i-a64-system-controller
> +
> +        - const: syscon
> +
> +      - contains:
> +          const: syscon
> +        additionalItems: true

If you want to match on all syscon nodes, you'll need a 'select' because 
'syscon' is now filtered out of the generated select.

> +
> +  reg:
> +    maxItems: 1
> +
> +  reg-io-width:
> +    description: |
> +      The size (in bytes) of the IO accesses that should be performed
> +      on the device.
> +    allOf:
> +      - $ref: /schemas/types.yaml#/definitions/uint32
> +      - enum: [ 1, 2, 4, 8 ]
> +
> +  hwlocks:
> +    maxItems: 1
> +    description:
> +      Reference to a phandle of a hardware spinlock provider node.
> +
> +required:
> +  - compatible
> +  - reg
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    syscon: syscon@1c00000 {
> +        compatible = "allwinner,sun8i-h3-system-controller", "syscon";
> +        reg = <0x01c00000 0x1000>;
> +    };
> +
> +  - |
> +    gpr: iomuxc-gpr@20e0000 {
> +        compatible = "fsl,imx6q-iomuxc-gpr", "syscon";
> +        reg = <0x020e0000 0x38>;
> +        hwlocks = <&hwlock1 1>;
> +    };
> +
> +...
> -- 
> 2.23.0
> 

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