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

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Message-ID: <99e0d2b9-d866-4b52-bde8-a6d89f35aadd@quicinc.com>
Date: Fri, 25 Apr 2025 13:01:10 -0700
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.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 4/25/2025 2:27 AM, Dmitry Baryshkov wrote:
> 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.
> 

Ok, so at this point of time, this is just the driver piece which does 
not have a real HW in the tree to be verified with.


>>
>>
>>>>> +
>>>>> +           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);
>>>
>>
> 
>