linux-kernel - Re: [PATCH 2/2] dt-bindings: display: Add "disable-hpd" binding

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Date:   Mon, 8 Feb 2021 10:18:00 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Mykyta Poturai <ddone@...ko.org>
Cc:     devicetree@...r.kernel.org, David Airlie <airlied@...ux.ie>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-renesas-soc@...r.kernel.org,
        Rob Herring <robh+dt@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>
Subject: Re: [PATCH 2/2] dt-bindings: display: Add "disable-hpd" binding

Hi,

On 31/01/2021 10:57, Mykyta Poturai wrote:
> Add the "disable-hpd" binding, used to disable hotplug detected
> functionality in the driver. When it's enabled the driver assumes that
> the connector is always connected and disables the hotplug detect
> related IRQ.

DT describes the hardware, not the software behaviour.

So if the HPD is broken, then add a "snps,broken-hpd" instead, or if you want to force output, use the DRM mode forcing, which is handled by the dw-hdmi code:
https://wiki.archlinux.org/index.php/kernel_mode_setting#Forcing_modes

Neil

> 
> Signed-off-by: Mykyta Poturai <ddone@...ko.org>
> ---
>  .../devicetree/bindings/display/bridge/renesas,dw-hdmi.txt       | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/Documentation/devicetree/bindings/display/bridge/renesas,dw-hdmi.txt b/Documentation/devicetree/bindings/display/bridge/renesas,dw-hdmi.txt
> index 3f6072651182..b2b899f46b86 100644
> --- a/Documentation/devicetree/bindings/display/bridge/renesas,dw-hdmi.txt
> +++ b/Documentation/devicetree/bindings/display/bridge/renesas,dw-hdmi.txt
> @@ -39,6 +39,7 @@ Optional properties:
>  
>  - power-domains: Shall reference the power domain that contains the DWC HDMI,
>    if any.
> +- disable-hpd: Disables the hotplug detect feature
>  
>  
>  Example:
>