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

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Message-ID: <CAO9ioeXhjrOyKz3N3oU6QxW+u6WUC4R5XXqWgb=7iF7Hk0Q_nQ@mail.gmail.com>
Date: Fri, 25 Apr 2025 12:27:55 +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 Fri, 25 Apr 2025 at 00:00, Abhinav Kumar <quic_abhinavk@...cinc.com> wrote:
>
>
>
> On 4/24/2025 3:23 AM, Dmitry Baryshkov wrote:
> > 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.
> >
>
> Yes but what I wanted to check was which LVDS panel was being used so
> far. Looks like for arm32 the dts is missing? As I couldnt find the lvds
> out endpoint. So can you pls point me to the lvds panel you verified
> this with?

I used the AUO b101xtn01 panel connected to the LVDS connector on the
IFC6410. I'm not posting DT bits since the panel is not a part of the
kit.

>
>
> >>> +
> >>> +           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