linux-kernel - Re: [PATCH v4 1/7] dt-bindings: Add panel-timing subnode to simple-panel

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Date:   Thu, 28 Mar 2019 17:26:49 -0300
From:   Ezequiel Garcia <ezequiel@...labora.com>
To:     Douglas Anderson <dianders@...omium.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Sean Paul <seanpaul@...omium.org>
Cc:     linux-rockchip@...ts.infradead.org,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        dri-devel@...ts.freedesktop.org,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Enric Balletbò <enric.balletbo@...labora.com>,
        Rob Herring <robh+dt@...nel.org>, mka@...omium.org,
        Eric Anholt <eric@...olt.net>,
        Jeffy Chen <jeffy.chen@...k-chips.com>,
        Stéphane Marchesin <marcheu@...omium.org>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        David Airlie <airlied@...ux.ie>,
        Mark Rutland <mark.rutland@....com>,
        Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH v4 1/7] dt-bindings: Add panel-timing subnode to
 simple-panel

On Thu, 2019-03-28 at 10:17 -0700, Douglas Anderson wrote:
> From: Sean Paul <seanpaul@...omium.org>
> 
> This patch adds a new subnode to simple-panel allowing us to override
> the typical timing expressed in the panel's display_timing.
> 
> Changes in v2:
>  - Split out the binding into a new patch (Rob)
>  - display-timings is a new section (Rob)
>  - Use the full display-timings subnode instead of picking the timing
>    out (Rob/Thierry)
> Changes in v3:
>  - Go back to using the timing subnode directly, but rename to
>    panel-timing (Rob)
> Changes in v4:
>  - Simplify desc. for when override should be used (Thierry/Laurent)
>  - Removed Rob H review since it's been a year and wording changed
> 
> Cc: Doug Anderson <dianders@...omium.org>
> Cc: Eric Anholt <eric@...olt.net>
> Cc: Heiko Stuebner <heiko@...ech.de>
> Cc: Jeffy Chen <jeffy.chen@...k-chips.com>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Stéphane Marchesin <marcheu@...omium.org>
> Cc: Thierry Reding <thierry.reding@...il.com>
> Cc: devicetree@...r.kernel.org
> Cc: dri-devel@...ts.freedesktop.org
> Cc: linux-rockchip@...ts.infradead.org
> Signed-off-by: Sean Paul <seanpaul@...omium.org>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> 
>  .../bindings/display/panel/simple-panel.txt   | 24 +++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/panel/simple-panel.txt b/Documentation/devicetree/bindings/display/panel/simple-panel.txt
> index b2b872c710f2..6157f86ddce4 100644
> --- a/Documentation/devicetree/bindings/display/panel/simple-panel.txt
> +++ b/Documentation/devicetree/bindings/display/panel/simple-panel.txt
> @@ -15,6 +15,18 @@ Optional properties:
>    (hot plug detect) signal, but the signal isn't hooked up so we should
>    hardcode the max delay from the panel spec when powering up the panel.
>  
> +panel-timing subnode
> +--------------------
> +
> +This optional subnode is for devices which require a mode differing
> +from the panel's "typical" display timing.  The panel timings provided
> +here will be ignored if they are found to be outside of allowable
> +ranges for the given panel.
> +

Is it OK to put this comment about how the implementation
will behave when values are out of range, given this is just a binding
spec?

Perhaps -if needed- this sentence can be rephrased to state that,
e.g. the OS may not be able to apply these values, if the controller
or device is unable to?

> +Format information on the panel-timing subnode can be found in
> +display-timing.txt.
> +
> +
>  Example:
>  
>  	panel: panel {
> @@ -25,4 +37,16 @@ Example:
>  		enable-gpios = <&gpio 90 0>;
>  
>  		backlight = <&backlight>;
> +
> +		panel-timing {
> +			clock-frequency = <266604720>;
> +			hactive = <2400>;
> +			hfront-porch = <48>;
> +			hback-porch = <84>;
> +			hsync-len = <32>;
> +			vactive = <1600>;
> +			vfront-porch = <3>;
> +			vback-porch = <120>;
> +			vsync-len = <10>;
> +		};
>  	};