linux-kernel - Re: [RFC PATCH v2 1/4] dt-bindings: clock: renesas: Document RZ/V2H(P) SoC CPG

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Date: Tue, 11 Jun 2024 09:02:26 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Prabhakar <prabhakar.csengg@...il.com>,
 Geert Uytterhoeven <geert+renesas@...der.be>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Magnus Damm <magnus.damm@...il.com>
Cc: linux-renesas-soc@...r.kernel.org, linux-clk@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 Fabrizio Castro <fabrizio.castro.jz@...esas.com>,
 Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [RFC PATCH v2 1/4] dt-bindings: clock: renesas: Document
 RZ/V2H(P) SoC CPG

On 11/06/2024 01:32, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> 
> Document the device tree bindings for the Renesas RZ/V2H(P) SoC
> Clock Pulse Generator (CPG).
> 
> CPG block handles the below operations:
> - Generation and control of clock signals for the IP modules
> - Generation and control of resets
> - Control over booting
> - Low power consumption and power supply domains
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>

Since this is not a finished work (RFC), only limited review follows.


> +$id: http://devicetree.org/schemas/clock/renesas,rzv2h-cpg.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Renesas RZ/V2H(P) Clock Pulse Generator (CPG)
> +
> +maintainers:
> +  - Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> +
> +description: |

Do not need '|' unless you need to preserve formatting.

> +  On Renesas RZ/V2H(P) SoCs, the CPG (Clock Pulse Generator) handles generation
> +  and control of clock signals for the IP modules, generation and control of resets,
> +  and control over booting, low power consumption and power supply domains.
> +
> +properties:
> +  compatible:
> +    const: renesas,r9a09g057-cpg
> +
> +  reg:
> +    maxItems: 1
> +
> +  clocks:
> +    maxItems: 1
> +
> +  clock-names:
> +    description:
> +      Clock source to CPG on QEXTAL pin.
> +    const: qextal
> +
> +  '#clock-cells':
> +    description: |
> +      - For CPG core clocks, the two clock specifier cells must be "CPG_CORE"
> +        and a core clock reference, as defined in
> +        <dt-bindings/clock/r9a09g057-cpg.h>,

So second cell is not used?

> +      - For module clocks, the two clock specifier cells must be "CPG_MOD" and
> +        a module number.  The module number is calculated as the CLKON register
> +        offset index multiplied by 16, plus the actual bit in the register
> +        used to turn the CLK ON. For example, for CGC_GIC_0_GICCLK, the
> +        calculation is (1 * 16 + 3) = 19.

You should not have different values. Make it const: 1 and just use IDs.

> +    const: 2
> +
> +  '#power-domain-cells':
> +    description:
> +      SoC devices that are part of the CPG/Module Standby Mode Clock Domain and
> +      can be power-managed through Module Standby should refer to the CPG device
> +      node in their "power-domains" property, as documented by the generic PM
> +      Domain bindings in Documentation/devicetree/bindings/power/power-domain.yaml.

Drop description, it's redundant.

> +    const: 0
> +
> +  '#reset-cells':
> +    description:
> +      The single reset specifier cell must be the reset number. The reset number
> +      is calculated as the reset register offset index multiplied by 16, plus the
> +      actual bit in the register used to reset the specific IP block. For example,
> +      for SYS_0_PRESETN, the calculation is (3 * 16 + 0) = 48.
> +    const: 1
> +
> +required:
> +  - compatible
> +  - reg
> +  - clocks
> +  - clock-names
> +  - '#clock-cells'
> +  - '#power-domain-cells'
> +  - '#reset-cells'
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    cpg: clock-controller@...20000 {

Drop unused label.

> +            compatible = "renesas,r9a09g057-cpg";

Use 4 spaces for example indentation.
> +    };

Best regards,
Krzysztof