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

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Date:   Tue, 21 Mar 2023 13:38:06 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Jayesh Choudhary <j-choudhary@...com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     andrzej.hajda@...el.com, neil.armstrong@...aro.org,
        rfoss@...nel.org, Laurent.pinchart@...asonboard.com,
        jonas@...boo.se, jernej.skrabec@...il.com, airlied@...il.com,
        daniel@...ll.ch, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, sam@...nborg.org,
        jani.nikula@...el.com, tzimmermann@...e.de, javierm@...hat.com,
        ville.syrjala@...ux.intel.com, r-ravikumar@...com,
        lyude@...hat.com, alexander.deucher@....com, sjakhade@...ence.com,
        yamonkar@...ence.com, a-bhatia1@...com
Subject: Re: [PATCH 1/2] dt-bindings: drm/bridge: Add no-hpd property

On 21/03/2023 13:02, Jayesh Choudhary wrote:
>>
>>> +    type: boolean
>>> +    description:
>>> +      Set if the HPD line on the bridge isn't hooked up to anything or is
>>> +      otherwise unusable.
>>
>> It's the property of the panel, not bridge. Unless you want to say that
>> bridge physically does not have HPD? Does it follow the standard in such
>> case?
> 
> MHDP does have hpd. But the mhdp driver should handle the cases when the

This is about bindings, not driver. Your driver can still handle this as
it wishes.

> hpd pin of bridge is not connected to that of the DP-connector. This is 
> to add support for that. (optional property)

Which is indicated by panel no-hpd, right? Or you mean now that HPD
physically cannot go to panel because it is cut on the bridge side? But
isn't this the same case (from hardware/bindings point, not driver) as
panel would not have HPD?


Best regards,
Krzysztof