linux-kernel - Re: [PATCH 2/2] drm: bridge: add enable gpio for display-connector

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Message-ID: <aQxZEi5oHsJUb/GR@hu-vvalluru-hyd.qualcomm.com>
Date: Thu, 6 Nov 2025 13:45:14 +0530
From: Prahlad Valluru <venkata.valluru@....qualcomm.com>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>, Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] drm: bridge: add enable gpio for display-connector

On Tue, Oct 28, 2025 at 05:49:29PM +0200, Laurent Pinchart wrote:
> On Tue, Oct 28, 2025 at 08:56:50PM +0530, Prahlad Valluru wrote:
> > In some cases, need gpio to be set for the connector
> > enable. Add optional enable gpio to display-connector.
> > 
> > Signed-off-by: Prahlad Valluru <venkata.valluru@....qualcomm.com>
> > ---
> >  drivers/gpu/drm/bridge/display-connector.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/bridge/display-connector.c b/drivers/gpu/drm/bridge/display-connector.c
> > index e9f16dbc9535..52f5e4175e64 100644
> > --- a/drivers/gpu/drm/bridge/display-connector.c
> > +++ b/drivers/gpu/drm/bridge/display-connector.c
> > @@ -21,6 +21,7 @@ struct display_connector {
> >  	struct drm_bridge	bridge;
> >  
> >  	struct gpio_desc	*hpd_gpio;
> > +	struct gpio_desc	*enable_gpio;
> >  	int			hpd_irq;
> >  
> >  	struct regulator	*supply;
> > @@ -298,6 +299,12 @@ static int display_connector_probe(struct platform_device *pdev)
> >  					     "Unable to retrieve HPD GPIO\n");
> >  
> >  		conn->hpd_irq = gpiod_to_irq(conn->hpd_gpio);
> > +
> > +		conn->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
> > +							 GPIOD_OUT_HIGH);
> 
> What does it mean to "enable the connector" ? Given that you don't set
> the GPIO value at runtime, this seems to be a hack that is probably
> better handled with GPIO hogs in the device tree.
DP_PWR 3.3v for the connector is enabled by a gpio. gpio hog will perfectly
work for this scenario, thanks for the suggestion.
> 
> > +		if (IS_ERR(conn->enable_gpio))
> > +			return dev_err_probe(&pdev->dev, PTR_ERR(conn->enable_gpio),
> > +					     "Unable to retrieve enable GPIO\n");
> >  	} else {
> >  		conn->hpd_irq = -EINVAL;
> >  	}
> 
> -- 
> Regards,
> 
> Laurent Pinchart