linux-kernel - Re: [PATCH v3 6/7] drm/msm/mdp4: switch LVDS to use drm_bridge/

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Message-ID: <s63lvzn35d7xcvw3kkmtasyinxbqa35juyxosdscfk6vhty4pw@hu3dotyklo3r>
Date: Thu, 24 Apr 2025 13:23:57 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 6/7] drm/msm/mdp4: switch LVDS to use
 drm_bridge/_connector

On Wed, Apr 23, 2025 at 07:04:16PM -0700, Abhinav Kumar wrote:
> 
> 
> On 2/26/2025 6:25 PM, Dmitry Baryshkov wrote:
> > LVDS support in MDP4 driver makes use of drm_connector directly. However
> > LCDC encoder and LVDS connector are wrappers around drm_panel. Switch
> > them to use drm_panel_bridge/drm_bridge_connector. This allows using
> > standard interface for the drm_panel and also inserting additional
> > bridges between encoder and panel.
> > 
> > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> > ---
> >   drivers/gpu/drm/msm/Makefile                       |   1 -
> >   drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c           |  34 +++++--
> >   drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.h           |   6 +-
> >   drivers/gpu/drm/msm/disp/mdp4/mdp4_lcdc_encoder.c  |  20 +----
> >   .../gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c    | 100 ---------------------
> >   5 files changed, 28 insertions(+), 133 deletions(-)
> > 
> > @@ -199,27 +201,43 @@ static int mdp4_modeset_init_intf(struct mdp4_kms *mdp4_kms,
> >   		 * bail out early if there is no panel node (no need to
> >   		 * initialize LCDC encoder and LVDS connector)
> >   		 */
> > -		panel_node = of_graph_get_remote_node(dev->dev->of_node, 0, 0);
> > -		if (!panel_node)
> > -			return 0;
> > +		next_bridge = devm_drm_of_get_bridge(dev->dev, dev->dev->of_node, 0, 0);
> > +		if (IS_ERR(next_bridge)) {
> > +			ret = PTR_ERR(next_bridge);
> > +			if (ret == -ENODEV)
> > +				return 0;
> > +			return ret;
> > +		}
> > -		encoder = mdp4_lcdc_encoder_init(dev, panel_node);
> > +		encoder = mdp4_lcdc_encoder_init(dev);
> >   		if (IS_ERR(encoder)) {
> >   			DRM_DEV_ERROR(dev->dev, "failed to construct LCDC encoder\n");
> > -			of_node_put(panel_node);
> >   			return PTR_ERR(encoder);
> >   		}
> >   		/* LCDC can be hooked to DMA_P (TODO: Add DMA_S later?) */
> >   		encoder->possible_crtcs = 1 << DMA_P;
> > -		connector = mdp4_lvds_connector_init(dev, panel_node, encoder);
> > +		ret = drm_bridge_attach(encoder, next_bridge, NULL, DRM_BRIDGE_ATTACH_NO_CONNECTOR);
> > +		if (ret) {
> > +			DRM_DEV_ERROR(dev->dev, "failed to attach LVDS panel/bridge: %d\n", ret);
> > +
> > +			return ret;
> > +		}
> 
> Can you pls point me to the lvds bridge used with this apq8064 board? I was
> unable to find it. Just wanted to compare that against this while reviewing.

It's the panel bridge, wrapping one of the LVDS panels.

> > +
> > +		connector = drm_bridge_connector_init(dev, encoder);
> >   		if (IS_ERR(connector)) {
> >   			DRM_DEV_ERROR(dev->dev, "failed to initialize LVDS connector\n");
> > -			of_node_put(panel_node);
> >   			return PTR_ERR(connector);
> >   		}
> > +		ret = drm_connector_attach_encoder(connector, encoder);
> > +		if (ret) {
> > +			DRM_DEV_ERROR(dev->dev, "failed to attach LVDS connector: %d\n", ret);
> > +
> > +			return ret;
> > +		}
> > +
> >   		break;
> >   	case DRM_MODE_ENCODER_TMDS:
> >   		encoder = mdp4_dtv_encoder_init(dev);

-- 
With best wishes
Dmitry