linux-kernel - Re: [PATCH v3 1/2] dt-bindings: drm/bridge: Add no-hpd property

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Message-ID: <5fec6e3d37a795b07874fb3fa136a01ab37ce113.camel@phytec.de>
Date: Thu, 20 Mar 2025 10:50:09 +0000
From: Dominik Haller <D.Haller@...tec.de>
To: Harikrishna Shenoy <h-shenoy@...com>, "andrzej.hajda@...el.com"
	<andrzej.hajda@...el.com>, "neil.armstrong@...aro.org"
	<neil.armstrong@...aro.org>, "rfoss@...nel.org" <rfoss@...nel.org>,
	"Laurent.pinchart@...asonboard.com" <Laurent.pinchart@...asonboard.com>,
	"jonas@...boo.se" <jonas@...boo.se>, "jernej.skrabec@...il.com"
	<jernej.skrabec@...il.com>, "simona@...ll.ch" <simona@...ll.ch>,
	"maarten.lankhorst@...ux.intel.com" <maarten.lankhorst@...ux.intel.com>,
	"mripard@...nel.org" <mripard@...nel.org>, "tzimmermann@...e.de"
	<tzimmermann@...e.de>, "robh@...nel.org" <robh@...nel.org>,
	"krzk+dt@...nel.org" <krzk+dt@...nel.org>, "conor+dt@...nel.org"
	<conor+dt@...nel.org>, "jani.nikula@...el.com" <jani.nikula@...el.com>,
	"j-choudhary@...com" <j-choudhary@...com>, "sui.jingfeng@...ux.dev"
	<sui.jingfeng@...ux.dev>, "viro@...iv.linux.org.uk"
	<viro@...iv.linux.org.uk>, "r-ravikumar@...com" <r-ravikumar@...com>,
	"sjakhade@...ence.com" <sjakhade@...ence.com>, "yamonkar@...ence.com"
	<yamonkar@...ence.com>, "dri-devel@...ts.freedesktop.org"
	<dri-devel@...ts.freedesktop.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/2]  dt-bindings: drm/bridge: Add no-hpd property

Hi,


On Wed, 2025-02-05 at 17:20 +0530, Harikrishna Shenoy wrote:
> From: Rahul T R <r-ravikumar@...com>
> 
> The mhdp bridge can work without its HPD pin hooked up to the
> connector,
> but the current bridge driver throws an error when hpd line is not
> connected to the connector. For such cases, we need an indication for
> no-hpd, using which we can bypass the hpd detection and instead use
> the
> auxiliary channels connected to the DP connector to confirm the
> connection.
> So add no-hpd property to the bindings, to disable hpd when not
> connected or unusable due to DP0-HPD not connected to correct HPD 
> pin on SOC like in case of J721S2.
out of curiosity. This series doesn't have anything to do with the
other DP HPD pin (AA24 MCASP1_ACLKX.DP0_HPD in case of J721S2) still
being mandatory to mux?
> Signed-off-by: Rahul T R <r-ravikumar@...com>
> Signed-off-by: Jayesh Choudhary <j-choudhary@...com>
> ---
>  .../devicetree/bindings/display/bridge/cdns,mhdp8546.yaml   | 6
> ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git
> a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
> b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
> index c2b369456e4e..3a6c6d837593 100644
> ---
> a/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
> +++
> b/Documentation/devicetree/bindings/display/bridge/cdns,mhdp8546.yaml
> @@ -57,6 +57,12 @@ properties:
>    interrupts:
>      maxItems: 1
>  
> +  cdns,no-hpd:
> +    type: boolean
> +    description:
> +      Set if the HPD line on the bridge isn't hooked up to anything
> or is
> +      otherwise unusable.
> +
>    ports:
>      $ref: /schemas/graph.yaml#/properties/ports
>