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

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Message-ID: <h24gpx6cxm4s6gzcunjnswubtvqask5dewi3udulmntsuieklm@w3pw4ig3t7gm>
Date: Wed, 5 Feb 2025 15:33:08 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Harikrishna Shenoy <h-shenoy@...com>, andrzej.hajda@...el.com, 
	neil.armstrong@...aro.org, rfoss@...nel.org, Laurent.pinchart@...asonboard.com, 
	jonas@...boo.se, jernej.skrabec@...il.com, simona@...ll.ch, 
	maarten.lankhorst@...ux.intel.com, mripard@...nel.org, tzimmermann@...e.de, robh@...nel.org, 
	krzk+dt@...nel.org, conor+dt@...nel.org, jani.nikula@...el.com, j-choudhary@...com, 
	sui.jingfeng@...ux.dev, viro@...iv.linux.org.uk, r-ravikumar@...com, 
	sjakhade@...ence.com, yamonkar@...ence.com, dri-devel@...ts.freedesktop.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] dt-bindings: drm/bridge: Add no-hpd property

On Wed, Feb 05, 2025 at 12:52:52PM +0100, Krzysztof Kozlowski wrote:
> On 05/02/2025 12:50, 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.
> > 
> > Signed-off-by: Rahul T R <r-ravikumar@...com>
> 
> Why are you sending over and over the same? You already got feedback.
> Then you send v2. You got the same feedback.
> 
> Now you send v3?
> 
> So the same feedback, but this time: NAK

Krzysztof's email forced me to take a look at the actual boards that you
are trying to enable. I couldn't stop by notice that the HPD signal
_is_ connected to a GPIO pin. Please stop hacking the bridge driver and
use the tools that are already provided to you: add the HPD pin to the
dp-controller device node. And then fix any possible issues coming from
the bridge driver not being able to handle HPD signals being delivered
by the DRM framework via the .hpd_notify() callback.

TL;DR: also a NAK from my side, add HPD gpio to dp-controller.

-- 
With best wishes
Dmitry