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

[Abhinav Kumar <quic_abhinavk@quicinc.com>]

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@linaro.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?


>>> +
>>> +		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);
>