linux-kernel - Re: [PATCH 1/2] dt-bindings: clock: fixed-factor: Add TI AM62 SoC OLDI clock

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Date:   Wed, 11 Jan 2023 11:44:59 -0800
From:   Stephen Boyd <sboyd@...nel.org>
To:     Aradhya Bhatia <a-bhatia1@...com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>
Cc:     Tomi Valkeinen <tomba@...nel.org>,
        Samuel Holland <samuel@...lland.org>,
        Maxime Ripard <mripard@...nel.org>,
        Linux Clock List <linux-clk@...r.kernel.org>,
        Devicetree List <devicetree@...r.kernel.org>,
        Linux Kernel List <linux-kernel@...r.kernel.org>,
        Nishanth Menon <nm@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Devarsh Thakkar <devarsht@...com>,
        Jai Luthra <j-luthra@...com>, Aradhya Bhatia <a-bhatia1@...com>
Subject: Re: [PATCH 1/2] dt-bindings: clock: fixed-factor: Add TI AM62 SoC OLDI clock

Quoting Aradhya Bhatia (2022-12-26 01:57:44)
> Add "ti,k3-am62-oldi-clk-div" to the fixed factor clock compatible enum
> list.
> 
> "ti,k3-am62-oldi-clk-div" is a fixed-factor clock that helps the TI
> display subsystem request a pixel clock for itself and a corresponding
> serial clock for its OLDI Transmitters. The serial clock is 7 times the
> pixel clock. This clock needs the clock set rate request to be
> propagated to the parent clock provider.
> 
> Signed-off-by: Aradhya Bhatia <a-bhatia1@...com>
> ---
>  Documentation/devicetree/bindings/clock/fixed-factor-clock.yaml | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/Documentation/devicetree/bindings/clock/fixed-factor-clock.yaml b/Documentation/devicetree/bindings/clock/fixed-factor-clock.yaml
> index 8f71ab300470..0696237530f7 100644
> --- a/Documentation/devicetree/bindings/clock/fixed-factor-clock.yaml
> +++ b/Documentation/devicetree/bindings/clock/fixed-factor-clock.yaml
> @@ -14,6 +14,7 @@ properties:
>    compatible:
>      enum:
>        - fixed-factor-clock
> +      - ti,k3-am62-oldi-clk-div

I don't see this compatible anywhere in the kernel tree. Is there a
patch that adds a node using this? I wonder why the display subsystem
can't add this fixed factor clk directly in the driver. Does the OLDI
Transmitter send a clk to the display subsystem?

I'm asking all these questions because we got rid of vendor compatibles
here in hopes of simplifying the logic. Maybe the problem can be
approached differently, but I don't know all the details.