linux-kernel - Re: [PATCH v6 16/18] dt-bindings: clock: imx8m-clock: support spread spectrum clocking

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Message-ID: <mne4dgxr2yl2gpzk2mzf7gcqynqupmqa6q6ibb6pa5xtao47sl@ylv2mhwboyzn>
Date: Mon, 23 Dec 2024 16:05:13 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Dario Binacchi <dario.binacchi@...rulasolutions.com>
Cc: linux-kernel@...r.kernel.org, linux-amarula@...rulasolutions.com, 
	Abel Vesa <abelvesa@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Fabio Estevam <festevam@...il.com>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Michael Turquette <mturquette@...libre.com>, Peng Fan <peng.fan@....com>, 
	Pengutronix Kernel Team <kernel@...gutronix.de>, Rob Herring <robh@...nel.org>, 
	Sascha Hauer <s.hauer@...gutronix.de>, Shawn Guo <shawnguo@...nel.org>, Stephen Boyd <sboyd@...nel.org>, 
	devicetree@...r.kernel.org, imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
	linux-clk@...r.kernel.org
Subject: Re: [PATCH v6 16/18] dt-bindings: clock: imx8m-clock: support spread
 spectrum clocking

On Sun, Dec 22, 2024 at 06:04:31PM +0100, Dario Binacchi wrote:
> The addition of DT bindings for enabling and tuning spread spectrum
> clocking generation can be applied specifically to the PLLs.
> 
> The "" value for the fsl,ssc-method property is specifically intended to
> specify a "no SSC" case, as in the example, when you don't want to
> configure spread spectrum for one of the PLLs, thus avoiding the use of
> a method that would only make sense if SSC were being set.
> 
> Signed-off-by: Dario Binacchi <dario.binacchi@...rulasolutions.com>
> 
> ---
> 
> Changes in v6:
> - Improve the commit message
> - change minItems from 7 to 1 for all the ssc properties added
> - change maxItems from 10 to 4 for alle the ssc properties added
> - update the DTS example
> 
> Changes in v4:
> - Drop "fsl,ssc-clocks" property. The other added properties now refer
>   to the clock list.
> - Updated minItems and maxItems of
>   - clocks
>   - clock-names
>   - fsl,ssc-modfreq-hz
>   - fsl,ssc-modrate-percent
>   - fsl,ssc-modmethod
> - Updated the dts examples
> 
> Changes in v3:
> - Added in v3
> - The dt-bindings have been moved from fsl,imx8m-anatop.yaml to
>   imx8m-clock.yaml. The anatop device (fsl,imx8m-anatop.yaml) is
>   indeed more or less a syscon, so it represents a memory area
>   accessible by ccm (imx8m-clock.yaml) to setup the PLLs.
> 
> Changes in v2:
> - Add "allOf:" and place it after "required:" block, like in the
>   example schema.
> - Move the properties definition to the top-level.
> - Drop unit types as requested by the "make dt_binding_check" command.
> 
>  .../bindings/clock/imx8m-clock.yaml           | 38 +++++++++++++++++++
>  1 file changed, 38 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/clock/imx8m-clock.yaml b/Documentation/devicetree/bindings/clock/imx8m-clock.yaml
> index 05bc01960045..37cc6a6e89d4 100644
> --- a/Documentation/devicetree/bindings/clock/imx8m-clock.yaml
> +++ b/Documentation/devicetree/bindings/clock/imx8m-clock.yaml
> @@ -43,6 +43,37 @@ properties:
>        ID in its "clocks" phandle cell. See include/dt-bindings/clock/imx8m-clock.h
>        for the full list of i.MX8M clock IDs.
>  
> +  fsl,ssc-modfreq-hz:
> +    description:
> +      The values of modulation frequency (Hz unit) for each clock
> +      supporting spread spectrum (i. e. audio_pll1, audio_pll2,
> +      dram_pll and video_pll).
> +    minItems: 1
> +    maxItems: 4

Please list the items. You rely here on this being in strict order, so
this should be explicit, instead of just "in example" in the
description.

items:
  - description: audio_pll1

> +
> +  fsl,ssc-modrate-percent:
> +    description:
> +      The percentage values of modulation rate for each clock
> +      supporting spread spectrum (i. e. audio_pll1, audio_pll2,
> +      dram_pll and video_pll).
> +    minItems: 1
> +    maxItems: 4

Ditto

> +
> +  fsl,ssc-modmethod:
> +    $ref: /schemas/types.yaml#/definitions/non-unique-string-array
> +    description:
> +      The modulation techniques for each clock supporting spread
> +      spectrum (i. e. audio_pll1, audio_pll2, dram_pll and
> +      video_pll).

I guess here listing items might not work, so:

  The modulation techniques for each clock supporting spread
  spectrum, in this order: audio_pll1, audio_pll2, dram_pll and video_pll

Everything looks good for me, so with above changes:

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>

Best regards,
Krzysztof