linux-kernel - Re: [RFC PATCH v2 3/6] ASoC: dt-bindings: Extend clock bindings of rt5659

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Date:   Mon, 28 Mar 2022 09:06:46 +0200
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Sameer Pujar <spujar@...dia.com>, broonie@...nel.org,
        lgirdwood@...il.com, robh+dt@...nel.org, krzk+dt@...nel.org,
        perex@...ex.cz, tiwai@...e.com, peter.ujfalusi@...ux.intel.com,
        pierre-louis.bossart@...ux.intel.com
Cc:     oder_chiou@...ltek.com, thierry.reding@...il.com,
        jonathanh@...dia.com, alsa-devel@...a-project.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org
Subject: Re: [RFC PATCH v2 3/6] ASoC: dt-bindings: Extend clock bindings of
 rt5659

On 28/03/2022 08:14, Sameer Pujar wrote:
> The rt5658 or rt5659 CODEC system clock (SYSCLK) can be derived from
> various clock sources. For example it can be derived either from master
> clock (MCLK) or by internal PLL. The internal PLL again can take input
> clock references from bit clocks (BCLKs) and MCLK. To enable a flexible
> clocking configuration the DT binding is extended here.
> 
> It makes use of standard clock bindings and sets up the clock relation
> via DT.
> 
> Signed-off-by: Sameer Pujar <spujar@...dia.com>
> Cc: Oder Chiou <oder_chiou@...ltek.com>
> ---
>  .../devicetree/bindings/sound/realtek,rt5659.yaml  | 53 ++++++++++++++++++++--
>  1 file changed, 49 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/sound/realtek,rt5659.yaml b/Documentation/devicetree/bindings/sound/realtek,rt5659.yaml
> index b0485b8..0c2f3cb 100644
> --- a/Documentation/devicetree/bindings/sound/realtek,rt5659.yaml
> +++ b/Documentation/devicetree/bindings/sound/realtek,rt5659.yaml
> @@ -29,12 +29,28 @@ properties:
>      maxItems: 1
>  
>    clocks:
> -    items:
> -      - description: Master clock (MCLK) to the CODEC
> +    description: |
> +      CODEC can receive multiple clock inputs like Master
> +      clock (MCLK), I2S bit clocks (BCLK1, BCLK2, BCLK3,
> +      BCLK4). The CODEC SYSCLK can be generated from MCLK
> +      or internal PLL. In turn PLL can reference from MCLK
> +      and BCLKs.
>  
>    clock-names:
> -    items:
> -      - const: mclk
> +    description: |
> +      The clock names can be combination of following:
> +        "mclk"        : Master clock
> +        "pll_ref"     : Reference to CODEC PLL clock
> +        "sysclk"      : CODEC SYSCLK
> +        "^bclk[1-4]$" : Bit clocks to CODEC

No, that does not look correct. You allow anything as clock input (even
20 clocks, different names, any order). That's not how DT schema should
work and that's not how hardware looks like.

Usually the clock inputs are always there which also you mentioned in
description - "multiple clock inputs". All these clocks should be
expected, unless really the wires (physical wires) can be left disconnected.

Best regards,
Krzysztof