linux-kernel - Re: [PATCH 1/2] dt-bindings: timer: add a binding for LiteX Timer

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Date:   Mon, 21 Nov 2022 11:19:32 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Icenowy Zheng <uwu@...nowy.me>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Karol Gugala <kgugala@...micro.com>,
        Mateusz Holenko <mholenko@...micro.com>,
        Gabriel Somlo <gsomlo@...il.com>, Joel Stanley <joel@....id.au>
Cc:     linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: timer: add a binding for LiteX Timer

On 21/11/2022 05:25, Icenowy Zheng wrote:
> The LiteX SoC generator has a timer core, which by default only
> generates a simple down counter.

Subject: drop second, redundant "bindings".

> 
> Add a DT binding for it.
> 
> Signed-off-by: Icenowy Zheng <uwu@...nowy.me>
> ---
>  .../bindings/timer/litex,timer.yaml           | 52 +++++++++++++++++++
>  1 file changed, 52 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/timer/litex,timer.yaml
> 
> diff --git a/Documentation/devicetree/bindings/timer/litex,timer.yaml b/Documentation/devicetree/bindings/timer/litex,timer.yaml
> new file mode 100644
> index 000000000000..bece07586c6b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/timer/litex,timer.yaml
> @@ -0,0 +1,52 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/timer/litex,timer.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: LiteX Timer
> +
> +maintainers:
> +  - Icenowy Zheng <uwu@...nowy.me>
> +
> +description: |
> +  The LiteX Timer is a count-down timer that is defaultly embedded
> +  into all LiteX SoCs, unless explicitly disabled. It's fed directly
> +  by the system clock like other LiteX peripherals.
> +
> +properties:
> +  compatible:
> +    const: litex,timer

No model name/number? If it is part of Soc, then a SoC specific number
is expected usually.

> +
> +  reg:
> +    maxItems: 1
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  clocks:
> +    maxItems: 1
> +
> +  litex,width:
> +    description:
> +      The width of the timer's value, specified as the width argument
> +      when creating an instance of litex.soc.cores.Timer.

This lacks type ($ref) and units in description, but more important -
why this is not part of compatible? Is it a width of register(s)?

And what is "instance of litex.soc.cores.Timer"? Is it configurable,
soft-core?

BTW, there is reg-io-width property.

> +
> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +  - clocks
> +  - litex,width
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +     timer@...06000 {

Use 4 spaces for example indentation.

> +        compatible = "litex,timer";
> +        reg = <0xa0006000 0x20>;
> +        clocks = <&sys_clk>;
> +        interrupts = <17>;
> +        litex,width = <32>;
> +     };

Best regards,
Krzysztof