Re: [PATCH 01/13] dt-bindings: clock: Add Amlogic A9 standardized model clock control units

[Krzysztof Kozlowski <krzk@kernel.org>]

On 09/02/2026 06:48, Chuan Liu via B4 Relay wrote:
> From: Chuan Liu <chuan.liu@amlogic.com>
> 
> Add dt-binding documentation for standardized model clock control units
> in A9 SoC family.
> 
> Signed-off-by: Chuan Liu <chuan.liu@amlogic.com>
> ---
>  .../bindings/clock/amlogic,a9-model-ccu.yaml       | 435 +++++++++++++++++++++
>  1 file changed, 435 insertions(+)

Brief review, you still have to read basic guidelines to not repeat the
basic mistakes.

> 
> diff --git a/Documentation/devicetree/bindings/clock/amlogic,a9-model-ccu.yaml b/Documentation/devicetree/bindings/clock/amlogic,a9-model-ccu.yaml
> new file mode 100644
> index 000000000000..56c5cbe1b246
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/clock/amlogic,a9-model-ccu.yaml
> @@ -0,0 +1,435 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +# Copyright (C) 2026 Amlogic, Inc. All rights reserved
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/clock/amlogic,a9-model-ccu.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Amlogic A9 Family Standardized Model Clock Control Unit
> +
> +maintainers:
> +  - Chuan Liu <chuan.liu@amlogic.com>
> +
> +description:
> +  The clock tree within the A9 is composed of numerous instances of these
> +  standardized model CCU (Clock Control Units).
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - items:

Drop

> +          - const: amlogic,a9-composite-ccu
> +        description: Supports clock source selection, frequency division, and
> +                     clock gating.

This is just one big enum. You can add comments if you insist...


> +      - items:
> +          - const: amlogic,a9-composite-ccu-mult
> +        description: Some modules have multiple input clocks and contain
> +                     multiple composite-ccus internally.
> +      - items:
> +          - const: amlogic,a9-noglitch-ccu
> +        description: Provides the same functionality as composite-ccu but
> +                     includes glitch suppression during frequency transitions.
> +      - items:
> +          - const: amlogic,a9-noglitch-ccu-mult
> +        description: Some modules have multiple input clocks and contain
> +                     multiple noglitch-ccus internally.
> +      - items:
> +          - const: amlogic,a9-sysbus-ccu
> +        description: Consists of multiple gating arrays, commonly used for
> +                     Amlogic's sys_clk and axi_clk.
> +
> +  reg:
> +    maxItems: 1
> +
> +  clocks:
> +    minItems: 1
> +    maxItems: 16
> +
> +  clock-names:
> +    minItems: 1
> +    maxItems: 16
> +
> +  clock-output-names:
> +    minItems: 1
> +    # The sysbus-ccu of A9 supports up to 128 gates
> +    maxItems: 128
> +
> +  '#clock-cells':
> +    description:
> +      The clock controller of a module may contain one or more CCU(s). When a
> +      clock controller has multiple CCUs, an index is required to specify a
> +      particular CCU within the clock controller.

Drop

> +    oneOf:
> +      - const: 0
> +        description: Single clock output, no specifier needed
> +      - const: 1
> +        description: Multiple clocks, index selects specific output

Drop all descriptions. That's enum. Do not explain usu how DT works.

> +
> +  amlogic,clock-max-frequency:

Drop property. So many wrong things here... First, start from basic
guidelines like talks or docs in kernel and understand the suffixes.

Second not a DT property.

> +    description: |
> +      Each clock's maximum output frequency is constrained during hardware
> +      design to ensure proper timing requirements for the clock network. If the
> +      clock frequency configured exceeds this design limit, it can lead to
> +      abnormal behavior in modules relying on that clock and may even cause
> +      cross-talk that affects other modules.
> +
> +      In the driver, this property is parsed, and interface functions from the

Why would we care about driver?

This is binding, we talk about hardware.


> +      CCF are called to enforce the clock's maximum frequency, preventing
> +      potential issues caused by excessive clock frequency configurations.
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +
> +  amlogic,reg-layout:

No, drop. Compatible defines it.

> +    description:
> +      These standardized model CCUs require register configuration for their
> +      clock functions. This property node describes the register layout
> +      parameters for each model's CCU.
> +    $ref: /schemas/types.yaml#/definitions/uint32-matrix
> +
> +allOf:
> +  - if:
> +      properties:
> +        compatible:
> +          anyOf:
> +            - contains:
> +                const: amlogic,a9-composite-ccu
> +            - contains:
> +                const: amlogic,a9-noglitch-ccu
> +    then:
> +      properties:
> +        '#clock-cells':
> +          const: 0
> +        clock-output-names:
> +          minItems: 1
> +          maxItems: 1
> +    else:
> +      properties:
> +        '#clock-cells':
> +          const: 1
> +        clock-output-names:
> +          minItems: 2
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: amlogic,a9-composite-ccu
> +    then:
> +      properties:
> +        clocks:
> +          minItems: 1
> +          items:
> +            - description: input clock source 0
> +            - description: input clock source 1 (optional)
> +            - description: input clock source 2 (optional)
> +            - description: input clock source 3 (optional)
> +            - description: input clock source 4 (optional)
> +            - description: input clock source 5 (optional)
> +            - description: input clock source 6 (optional)
> +            - description: input clock source 7 (optional)
> +        clock-names:
> +          minItems: 1
> +          items:
> +            - const: clkin0
> +            - const: clkin1
> +            - const: clkin2
> +            - const: clkin3
> +            - const: clkin4
> +            - const: clkin5
> +            - const: clkin6
> +            - const: clkin7
> +        amlogic,reg-layout:
> +          description: |
> +            composite-ccu contains three register layout parameters:
> +              * register offset
> +              * bit offset
> +              * divider effective bit width
> +      required:
> +        - amlogic,reg-layout
> +        - clock-names
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: amlogic,a9-composite-ccu-mult
> +    then:
> +      properties:
> +        clocks:
> +          description:
> +            Some clock controllers contain two composite-ccus (labeled
> +            composite_a and composite_b). In certain controllers, composite_a
> +            and composite_b share a common clock source, while in others they
> +            have independent clock sources.
> +          minItems: 1
> +          items:
> +            - description: composite_a/b's input clock source 0
> +            - description: composite_a/b's input clock source 1 (optional)
> +            - description: composite_a/b's input clock source 2 (optional)
> +            - description: composite_a/b's input clock source 3 (optional)
> +            - description: composite_a/b's input clock source 4 (optional)
> +            - description: composite_a/b's input clock source 5 (optional)
> +            - description: composite_a/b's input clock source 6 (optional)
> +            - description: composite_a/b's input clock source 7 (optional)
> +            - description: composite_b's input clock source 0 (optional)
> +            - description: composite_b's input clock source 1 (optional)
> +            - description: composite_b's input clock source 2 (optional)
> +            - description: composite_b's input clock source 3 (optional)
> +            - description: composite_b's input clock source 4 (optional)
> +            - description: composite_b's input clock source 5 (optional)
> +            - description: composite_b's input clock source 6 (optional)
> +            - description: composite_b's input clock source 7 (optional)
> +        clock-names:
> +          minItems: 1
> +          items:
> +            - const: clkin0
> +            - const: clkin1
> +            - const: clkin2
> +            - const: clkin3
> +            - const: clkin4
> +            - const: clkin5
> +            - const: clkin6
> +            - const: clkin7
> +            - const: bclkin0
> +            - const: bclkin1
> +            - const: bclkin2
> +            - const: bclkin3
> +            - const: bclkin4
> +            - const: bclkin5
> +            - const: bclkin6
> +            - const: bclkin7
> +        amlogic,reg-layout:
> +          description: |
> +            composite-ccu contains three register layout parameters:
> +              * register offset
> +              * bit offset
> +              * divider effective bit width
> +      required:
> +        - amlogic,reg-layout
> +        - clock-names
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: amlogic,a9-noglitch-ccu
> +    then:
> +      properties:
> +        clocks:
> +          minItems: 1
> +          items:
> +            - description: input clock source 0
> +            - description: input clock source 1 (optional)
> +            - description: input clock source 2 (optional)
> +            - description: input clock source 3 (optional)
> +            - description: input clock source 4 (optional)
> +            - description: input clock source 5 (optional)
> +            - description: input clock source 6 (optional)
> +            - description: input clock source 7 (optional)
> +        clock-names:
> +          minItems: 1
> +          items:
> +            - const: clkin0
> +            - const: clkin1
> +            - const: clkin2
> +            - const: clkin3
> +            - const: clkin4
> +            - const: clkin5
> +            - const: clkin6
> +            - const: clkin7
> +      required:
> +        - clock-names
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: amlogic,a9-noglitch-ccu-mult
> +    then:
> +      properties:
> +        clocks:
> +          minItems: 1

Why?

> +          items:
> +            - description: input clock source 0
> +            - description: input clock source 1 (optional)

Drop optional. Don't repeat constraints in free form text.

> +            - description: input clock source 2 (optional)
> +            - description: input clock source 3 (optional)
> +            - description: input clock source 4 (optional)
> +            - description: input clock source 5 (optional)
> +            - description: input clock source 6 (optional)
> +            - description: input clock source 7 (optional)
> +        clock-names:
> +          minItems: 1
> +          items:
> +            - const: clkin0
> +            - const: clkin1
> +            - const: clkin2
> +            - const: clkin3
> +            - const: clkin4
> +            - const: clkin5
> +            - const: clkin6
> +            - const: clkin7
> +        amlogic,reg-layout:
> +          description: |
> +            composite-ccu contains one register layout parameters:
> +              * register offset
> +      required:
> +        - amlogic,reg-layout
> +        - clock-names
> +
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: amlogic,a9-sysbus-ccu
> +    then:
> +      properties:
> +        clocks:
> +          maxItems: 1
> +          description: input clock of sysbus-ccu

list the items with description instead.

> +        amlogic,reg-layout:
> +          description: |
> +            composite-ccu contains two register layout parameters:
> +              * register offset
> +              * bit offset
> +      required:
> +        - amlogic,reg-layout

This is huge and amount of ifs is clearly suggesting you combined way
too much into one file.


> +
> +required:
> +  - compatible
> +  - reg
> +  - clocks
> +  - clock-output-names
> +  - "#clock-cells"
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    clk_dummy: clock-dummy {
> +        compatible = "fixed-clock";
> +        #clock-cells = <0>;
> +        clock-frequency = <0>;
> +        clock-output-names = "dummy";
> +        status = "disabled";
> +    };

Not relevant, drop entire node.

> +
> +    apb {
> +        #address-cells = <2>;
> +        #size-cells = <2>;
> +        clock-controller@350 {
> +            compatible = "amlogic,a9-composite-ccu";
> +            reg = <0x0 0x350 0x0 0x4>;
> +            #clock-cells = <0>;
> +            amlogic,clock-max-frequency = <50000000>;
> +            amlogic,reg-layout = <0x0 0  7>;
> +            clock-output-names = "sar_adc";
> +            clocks = <&xtal_24m>,
> +                     <&scmi_clk 17>;
> +            clock-names = "clkin0", "clkin1";
> +        };
> +
> +        clock-controller@290 {
> +            compatible = "amlogic,a9-composite-ccu-mult";
> +            reg = <0x0 0x290 0x0 0x8>;
> +            #clock-cells = <1>;
> +            amlogic,clock-max-frequency = <250000000>,
> +                                          <250000000>,
> +                                          <1200000000>;
> +            amlogic,reg-layout = <0x0 0  7>,
> +                                 <0x0 16 7>,
> +                                 <0x4 0  7>;
> +            clock-output-names = "sd_emmc_a",
> +                                 "sd_emmc_b",
> +                                 "sd_emmc_c";
> +            clocks = <&xtal_24m>,
> +                     <&scmi_clk 6>,
> +                     <&scmi_clk 10>;
> +            clock-names = "clkin0",
> +                          "clkin1",
> +                          "clkin2";
> +        };

One or two are enough. Drop the rest.

> 


Best regards,
Krzysztof

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