linux-kernel - Re: [PATCH V8 7/7] dt-bindings: bridge: samsung-dsim: Make some flags optional

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Date:   Fri, 26 May 2023 19:19:01 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Adam Ford <aford173@...il.com>
Cc:     dri-devel@...ts.freedesktop.org, aford@...conembedded.com,
        Inki Dae <inki.dae@...sung.com>,
        Jagan Teki <jagan@...rulasolutions.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Frieder Schrempf <frieder.schrempf@...tron.de>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V8 7/7] dt-bindings: bridge: samsung-dsim: Make some
 flags optional

Adam, Neil,

I meant to get to this earlier today, but broken CI got in the way...

On Thu, May 25, 2023 at 10:05:59PM -0500, Adam Ford wrote:
> In the event a device is connected to the samsung-dsim
> controller that doesn't support the burst-clock, the
> driver is able to get the requested pixel clock from the
> attached device or bridge.  In these instances, the
> samsung,burst-clock-frequency isn't needed, so remove
> it from the required list.
> 
> The pll-clock frequency can be set by the device tree entry
> for samsung,pll-clock-frequency, but in some cases, the
> pll-clock may have the same clock rate as sclk_mipi clock.
> If they are equal, this flag is not needed since the driver
> will use the sclk_mipi rate as a fallback.
> 
> Signed-off-by: Adam Ford <aford173@...il.com>
> ---
>  .../bindings/display/bridge/samsung,mipi-dsim.yaml       | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/samsung,mipi-dsim.yaml b/Documentation/devicetree/bindings/display/bridge/samsung,mipi-dsim.yaml
> index 9f61ebdfefa8..360fea81f4b6 100644
> --- a/Documentation/devicetree/bindings/display/bridge/samsung,mipi-dsim.yaml
> +++ b/Documentation/devicetree/bindings/display/bridge/samsung,mipi-dsim.yaml
> @@ -70,7 +70,9 @@ properties:
>    samsung,burst-clock-frequency:
>      $ref: /schemas/types.yaml#/definitions/uint32
>      description:
> -      DSIM high speed burst mode frequency.
> +      DSIM high speed burst mode frequency when connected to devices
> +      that support burst mode. If absent, the driver will use the pixel
> +      clock from the attached device or bridge.

I'd rather this description did not say anything about drivers.
How about:
	If absent, the pixel clock from the attached device or bridge
	will be used instead.
Or perhaps "must be used"? Ditto below.

Description aside, the removal seems to be backwards compatible - but
can every device that this binding supports work using an "attached
device or bridge", or are these properties going to be required for
certain compatibles?

Thanks,
Conor.

>  
>    samsung,esc-clock-frequency:
>      $ref: /schemas/types.yaml#/definitions/uint32
> @@ -80,7 +82,8 @@ properties:
>    samsung,pll-clock-frequency:
>      $ref: /schemas/types.yaml#/definitions/uint32
>      description:
> -      DSIM oscillator clock frequency.
> +      DSIM oscillator clock frequency. If absent, the driver will
> +      use the clock frequency of sclk_mipi.
>  
>    phys:
>      maxItems: 1
> @@ -134,9 +137,7 @@ required:
>    - compatible
>    - interrupts
>    - reg
> -  - samsung,burst-clock-frequency
>    - samsung,esc-clock-frequency
> -  - samsung,pll-clock-frequency
>  
>  allOf:
>    - $ref: ../dsi-controller.yaml#
> -- 
> 2.39.2
> 

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