Re: [PATCH v5 1/6] dt-bindings: pwm: Add a new binding for rockchip,rk3576-pwm

Uwe Kleine-König <[email protected]> Fri, 10 Jul 2026 12:31:35 +0200

Newsgroups	org.kernel.vger.linux-pwm,org.infradead.lists.linux-arm-kernel,org.infradead.lists.linux-rockchip,org.kernel.vger.linux-devicetree,org.kernel.vger.linux-iio,org.kernel.vger.linux-kernel
Message-ID	<alCvmLX1ke0qjh99@monoceros>

Hello,

On Mon, Apr 20, 2026 at 03:52:38PM +0200, Nicolas Frattaroli wrote:
> The Rockchip RK3576 SoC has a newer PWM controller IP revision than
> previous Rockchip SoCs. This IP, called "PWMv4" by Rockchip, introduces
> several new features, and consequently differs in its bindings.
> 
> Instead of expanding the ever-growing rockchip-pwm binding that already
> has an if-condition, add an entirely new binding to handle this.
> 
> There are two additional clocks, "osc" and "rc". These are available for
> every PWM instance, and the PWM hardware can switch between the "pwm",
> "osc" and "rc" clock at runtime.
> 
> The PWM controller also comes with an interrupt now. This interrupt is
> used to signal various conditions.
> 
> Reviewed-by: Conor Dooley <[email protected]>
> Reviewed-by: Rob Herring (Arm) <[email protected]>
> Signed-off-by: Nicolas Frattaroli <[email protected]>
> ---
>  .../bindings/pwm/rockchip,rk3576-pwm.yaml          | 77 ++++++++++++++++++++++
>  MAINTAINERS                                        |  7 ++
>  2 files changed, 84 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/pwm/rockchip,rk3576-pwm.yaml b/Documentation/devicetree/bindings/pwm/rockchip,rk3576-pwm.yaml
> new file mode 100644
> index 000000000000..48d5055c8b06
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pwm/rockchip,rk3576-pwm.yaml
> @@ -0,0 +1,77 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/pwm/rockchip,rk3576-pwm.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Rockchip PWMv4 controller
> +
> +maintainers:
> +  - Nicolas Frattaroli <[email protected]>
> +
> +description: |
> +  The Rockchip PWMv4 controller is a PWM controller found on several Rockchip
> +  SoCs, such as the RK3576.
> +
> +  It supports both generating and capturing PWM signals.
> +
> +allOf:
> +  - $ref: pwm.yaml#
> +
> +properties:
> +  compatible:
> +    items:
> +      - const: rockchip,rk3576-pwm
> +
> +  reg:
> +    maxItems: 1
> +
> +  clocks:
> +    items:
> +      - description: Used to derive the PWM signal.
> +      - description: Used as the APB bus clock.
> +      - description: Used as an alternative to derive the PWM signal.
> +      - description: Used as another alternative to derive the PWM signal.
> +
> +  clock-names:
> +    items:
> +      - const: pwm
> +      - const: pclk
> +      - const: osc
> +      - const: rc
> +
> +  interrupts:
> +    maxItems: 1
> +
> +  "#pwm-cells":
> +    const: 3
> +
> +required:
> +  - compatible
> +  - reg
> +  - clocks
> +  - clock-names
> +  - interrupts

pwm.yaml has:

	required:
	  - "#pwm-cells"

Still Sashiko[1] claims:

	The binding defines #pwm-cells under properties, but omitting it from the
	required list allows device tree nodes missing the property to pass schema
	validation.

I played a bit around with dt-validate and I think Sashiko is wrong here
and pwm.yaml's requirement isn't overridden by the local required list.

So this patch should be fine.

Best regards
Uwe

[1] https://sashiko.dev/#/patchset/20260420-rk3576-pwm-v5-0-ae7cfbbe5427%40collabora.com

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