linux-kernel - Re: [RFC PATCH 02/16] dt-bindings: display: rockchip: Add EBC binding

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Date:   Thu, 14 Apr 2022 10:15:48 +0200
From:   Andreas Kemnade <andreas@...nade.info>
To:     Samuel Holland <samuel@...lland.org>
Cc:     Heiko Stübner <heiko@...ech.de>,
        Sandy Huang <hjc@...k-chips.com>,
        dri-devel@...ts.freedesktop.org,
        linux-rockchip@...ts.infradead.org,
        Alistair Francis <alistair@...stair23.me>,
        Ondřej Jirman <x@....cz>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Liang Chen <cl@...k-chips.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Michael Riesch <michael.riesch@...fvision.net>,
        Nicolas Frattaroli <frattaroli.nicolas@...il.com>,
        Peter Geis <pgwipeout@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 02/16] dt-bindings: display: rockchip: Add EBC
 binding

Hi Samuel,

for comparison, here is my submission for the IMX EPDC bindings:

https://lore.kernel.org/linux-devicetree/20220206080016.796556-2-andreas@kemnade.info/

On Wed, 13 Apr 2022 17:19:02 -0500
Samuel Holland <samuel@...lland.org> wrote:

[...]
we have sy7636a driver in kernel which should be suitable for powering a EPD
and temperature measurement. So I would expect that to be 
> +  io-channels:
> +    maxItems: 1
> +    description: I/O channel for panel temperature measurement
> +
so how would I reference the hwmon/thermal(-zone) of the sy7636a here?

> +  panel-supply:
> +    description: Regulator supplying the panel's logic voltage
> +
> +  power-domains:
> +    maxItems: 1
> +
> +  vcom-supply:
> +    description: Regulator supplying the panel's compensation voltage
> +
> +  vdrive-supply:
> +    description: Regulator supplying the panel's gate and source drivers
> +
SY7636a has only one logical regulator in kernel for for the latter two.

If we have a separate panel node, than maybe these regulators should go
there as they belong to the panel as they are powering the panel and
not the EBC.

> +  port:
> +    $ref: /schemas/graph.yaml#/properties/port
> +    description: OF graph port for the attached display panel
> +
In my approach for the IMX EPDC, (I will send a better commented one
soon) I have no separate subnode to avoid messing with additional
display parameters. Not sure what is really better here.

> +required:
> +  - compatible
> +  - reg
> +  - interrupts
> +  - clocks
> +  - clock-names
> +  - resets
> +  - reset-names
> +  - power-domains
> +  - panel-supply
> +  - vcom-supply
> +  - vdrive-supply

If things differ how the different phyiscally existing regulators are
mapped into logical ones (even the vdrive supply is still a bunch of
physical regulators mapped into one logical one), then not everything
can be required.

Regards,
Andreas