Re: [PATCH v1 1/2] dt-bindings: i3c: Add NPCM845 i3c controller

Krzysztof Kozlowski
2024-08-01T14:54:02Z

On 01/08/2024 09:19, Stanley Chu wrote:
> The npcm845 i3c devicetree binding follows the basic i3c bindings
> and add the properties for allowing to adjust the SDA/SCL timing
> to meet different requirements.
>
> Signed-off-by: Stanley Chu <yschu@nuvoton.com>
> Signed-off-by: James Chiang <cpchiang1@nuvoton.com>
> ---
> .../bindings/i3c/nuvoton,i3c-master.yaml | 123 ++++++++++++++++++

Use compatible as filename. Anyway word "master" was dropped.

> 1 file changed, 123 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/i3c/nuvoton,i3c-master.yaml
>
> diff --git a/Documentation/devicetree/bindings/i3c/nuvoton,i3c-master.yaml b/Documentation/devicetree/bindings/i3c/nuvoton,i3c-master.yaml
> new file mode 100644
> index 000000000000..a40b37b16872
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/i3c/nuvoton,i3c-master.yaml
> @@ -0,0 +1,123 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/i3c/nuvoton,i3c-master.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Nuvoton NPCM845 I3C master

Use new terminology. Since 2021 there was a change... three years ago.

> +
> +maintainers:
> + - Stanley Chu <yschu@nuvoton.com>
> + - James Chiang <cpchiang1@nuvoton.com>
> +
> +allOf:
> + - $ref: i3c.yaml#
> +
> +properties:
> + compatible:
> + const: nuvoton,npcm845-i3c
> +
> + reg:
> + items:
> + - description: I3C registers
> + - description: GDMA registers
> + - description: GDMA request control register
> +
> + reg-names:
> + items:
> + - const: i3c
> + - const: dma
> + - const: dma_ctl
> +
> + interrupts:
> + maxItems: 1
> +
> + clocks:
> + items:
> + - description: system clock
> + - description: bus clock
> +
> + clock-names:
> + items:
> + - const: pclk
> + - const: fast_clk
> +
> + resets:
> + maxItems: 1
> +
> + i3c-pp-scl-hi-period-ns:
> + description: |

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

> + If need to configure SCL with required duty cycle, specify the clock high/low period directly.
> + i3c-pp-scl-hi-perios-ns specifies the high period ns of the SCL clock cycle in push pull mode
> + When i3c-pp-scl-hi-period-ns and i3c-pp-scl-lo-period-ns are specified, the i3c pp frequency is
> + decided by these two properties.

Wrap according to Linux Coding Style (and read coding style to figure
the proper wrapping...).

> +
> + i3c-pp-scl-lo-period-ns:
> + description: |
> + The low period ns of the SCL clock cycle in push pull mode. i3c-pp-scl-lo-period-ns should not
> + be less than i3c-pp-scl-hi-period-ns and the maximal value is i3c-pp-scl-hi-period-ns + 150.

Everywhere: defaults, constraints.

> +
> + i3c-pp-sda-rd-skew:
> + $ref: /schemas/types.yaml#/definitions/uint32
> + description: |
> + The number of MCLK clock periods to delay the SDA transition from the SCL clock edge at push
> + pull operation when transfers i3c private read.
> + maximum: 7
> + default: 0
> +
> + i3c-pp-sda-wr-skew:
> + $ref: /schemas/types.yaml#/definitions/uint32
> + description: |
> + The number of MCLK clock periods to delay the SDA transition from the SCL clock edge at push
> + pull operation when transfers i3c private write.
> + maximum: 7
> + default: 0
> +
> + i3c-od-scl-hi-period-ns:
> + description: |
> + The i3c open drain frequency is 1MHz by default.
> + If need to use different frequency, specify the clock high/low period directly.
> + i3c-od-scl-hi-perios-ns specifies the high period ns of the SCL clock cycle in open drain mode.
> + When i3c-od-scl-hi-period-ns and i3c-od-scl-lo-period-ns are specified, the i3c od frequency is
> + decided by these two properties.
> + i3c-od-scl-hi-period-ns should be equal to i3c-pp-scl-hi-period-ns or i3c-od-scl-lo-period-ns.
> +
> + i3c-od-scl-lo-period-ns:
> + description: |
> + The low period ns of the SCL clock cycle in open drain mode. i3c-od-scl-lo-period-ns should be
> + multiple of i3c-pp-scl-hi-period-ns.
> +
> + enable-hj:
> + type: boolean
> + description: |
> + Enable SLVSTART interrupt for receiving hot-join request.

You described the desired Linux feature or behavior, not the actual
hardware. The bindings are about the latter, so instead you need to
rephrase the property and its description to match actual hardware
capabilities/features/configuration etc.

> +
> + use-dma:
> + type: boolean
> + description: |
> + Enable the i3c private transfers using DMA.

Why wouldn't you enable it always? Where are dma properties for this?

> +
> +required:
> + - compatible
> + - reg
> + - interrupts
> + - clock-names
> + - clocks
> +
> +additionalProperties: true

Nope, it cannot be true. Look how other bindings are doing this. Why
implementing something entirely different?

> +
> +examples:
> + - |
> + i3c@fff10000 {
> + compatible = "nuvoton,npcm845-i3c";
> + clocks = <&clk 4>, <&clk 26>;
> + clock-names = "pclk", "fast_clk";
> + interrupts = <0 224 4>;
> + reg = <0xfff10000 0x1000>,
> + <0xf0850000 0x1000>,
> + <0xf0800300 0x4>;

Order properties as in DTS coding style.

> + reg-names = "i3c", "dma", "dma_ctl";
> + resets = <&rstc 0x74 8>;
> + #address-cells = <3>;
> + #size-cells = <0>;

Make your bindings complete - you skipped many properties. Why defining
them if you are not using them and they do not have defaults?

> + };

Best regards,
Krzysztof