drm/panel: simple: restore connector_type fallback

The switch from devm_kzalloc() + drm_panel_init() to
devm_drm_panel_alloc() introduced a regression.

Several panel descriptors do not set connector_type. For those panels,
panel_simple_probe() used to compute a connector type (currently DPI as a
fallback) and pass that value to drm_panel_init(). After the conversion
to devm_drm_panel_alloc(), the call unconditionally used
desc->connector_type instead, ignoring the computed fallback and
potentially passing DRM_MODE_CONNECTOR_Unknown, which
drm_panel_bridge_add() does not allow.

Move the connector_type validation / fallback logic before the
devm_drm_panel_alloc() call and pass the computed connector_type to
devm_drm_panel_alloc(), so panels without an explicit connector_type
once again get the DPI default.

Signed-off-by: Ludovic Desroches <[e-mail]>
Fixes: de04bb0089a9 ("drm/panel/panel-simple: Use the new allocation in place of devm_kzalloc()")
Cc: [e-mail]
Reviewed-by: Luca Ceresoli <[e-mail]>
Link: https://lore.kernel.org/stable/20251126-lcd_panel_connector_type_fix-v2-1-c15835d1f7cb%40microchip.com
Signed-off-by: Neil Armstrong <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

drivers/gpu/drm/panel/panel-simple.c

···
 	if (IS_ERR(desc))
 		return ERR_CAST(desc);
 
+	connector_type = desc->connector_type;
+	/* Catch common mistakes for panels. */
+	switch (connector_type) {
+	case 0:
+		dev_warn(dev, "Specify missing connector_type\n");
+		connector_type = DRM_MODE_CONNECTOR_DPI;
+		break;
+	case DRM_MODE_CONNECTOR_LVDS:
+		WARN_ON(desc->bus_flags &
+			~(DRM_BUS_FLAG_DE_LOW |
+			  DRM_BUS_FLAG_DE_HIGH |
+			  DRM_BUS_FLAG_DATA_MSB_TO_LSB |
+			  DRM_BUS_FLAG_DATA_LSB_TO_MSB));
+		WARN_ON(desc->bus_format != MEDIA_BUS_FMT_RGB666_1X7X3_SPWG &&
+			desc->bus_format != MEDIA_BUS_FMT_RGB888_1X7X4_SPWG &&
+			desc->bus_format != MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA);
+		WARN_ON(desc->bus_format == MEDIA_BUS_FMT_RGB666_1X7X3_SPWG &&
+			desc->bpc != 6);
+		WARN_ON((desc->bus_format == MEDIA_BUS_FMT_RGB888_1X7X4_SPWG ||
+			 desc->bus_format == MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA) &&
+			desc->bpc != 8);
+		break;
+	case DRM_MODE_CONNECTOR_eDP:
+		dev_warn(dev, "eDP panels moved to panel-edp\n");
+		return ERR_PTR(-EINVAL);
+	case DRM_MODE_CONNECTOR_DSI:
+		if (desc->bpc != 6 && desc->bpc != 8)
+			dev_warn(dev, "Expected bpc in {6,8} but got: %u\n", desc->bpc);
+		break;
+	case DRM_MODE_CONNECTOR_DPI:
+		bus_flags = DRM_BUS_FLAG_DE_LOW |
+			    DRM_BUS_FLAG_DE_HIGH |
+			    DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE |
+			    DRM_BUS_FLAG_PIXDATA_SAMPLE_NEGEDGE |
+			    DRM_BUS_FLAG_DATA_MSB_TO_LSB |
+			    DRM_BUS_FLAG_DATA_LSB_TO_MSB |
+			    DRM_BUS_FLAG_SYNC_SAMPLE_POSEDGE |
+			    DRM_BUS_FLAG_SYNC_SAMPLE_NEGEDGE;
+		if (desc->bus_flags & ~bus_flags)
+			dev_warn(dev, "Unexpected bus_flags(%d)\n", desc->bus_flags & ~bus_flags);
+		if (!(desc->bus_flags & bus_flags))
+			dev_warn(dev, "Specify missing bus_flags\n");
+		if (desc->bus_format == 0)
+			dev_warn(dev, "Specify missing bus_format\n");
+		if (desc->bpc != 6 && desc->bpc != 8)
+			dev_warn(dev, "Expected bpc in {6,8} but got: %u\n", desc->bpc);
+		break;
+	default:
+		dev_warn(dev, "Specify a valid connector_type: %d\n", desc->connector_type);
+		connector_type = DRM_MODE_CONNECTOR_DPI;
+		break;
+	}
+
 	panel = devm_drm_panel_alloc(dev, struct panel_simple, base,
-				     &panel_simple_funcs, desc->connector_type);
+				     &panel_simple_funcs, connector_type);
 	if (IS_ERR(panel))
 		return ERR_CAST(panel);
 
···
 		err = panel_simple_override_nondefault_lvds_datamapping(dev, panel);
 		if (err)
 			goto free_ddc;
-	}
-
-	connector_type = desc->connector_type;
-	/* Catch common mistakes for panels. */
-	switch (connector_type) {
-	case 0:
-		dev_warn(dev, "Specify missing connector_type\n");
-		connector_type = DRM_MODE_CONNECTOR_DPI;
-		break;
-	case DRM_MODE_CONNECTOR_LVDS:
-		WARN_ON(desc->bus_flags &
-			~(DRM_BUS_FLAG_DE_LOW |
-			  DRM_BUS_FLAG_DE_HIGH |
-			  DRM_BUS_FLAG_DATA_MSB_TO_LSB |
-			  DRM_BUS_FLAG_DATA_LSB_TO_MSB));
-		WARN_ON(desc->bus_format != MEDIA_BUS_FMT_RGB666_1X7X3_SPWG &&
-			desc->bus_format != MEDIA_BUS_FMT_RGB888_1X7X4_SPWG &&
-			desc->bus_format != MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA);
-		WARN_ON(desc->bus_format == MEDIA_BUS_FMT_RGB666_1X7X3_SPWG &&
-			desc->bpc != 6);
-		WARN_ON((desc->bus_format == MEDIA_BUS_FMT_RGB888_1X7X4_SPWG ||
-			 desc->bus_format == MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA) &&
-			desc->bpc != 8);
-		break;
-	case DRM_MODE_CONNECTOR_eDP:
-		dev_warn(dev, "eDP panels moved to panel-edp\n");
-		err = -EINVAL;
-		goto free_ddc;
-	case DRM_MODE_CONNECTOR_DSI:
-		if (desc->bpc != 6 && desc->bpc != 8)
-			dev_warn(dev, "Expected bpc in {6,8} but got: %u\n", desc->bpc);
-		break;
-	case DRM_MODE_CONNECTOR_DPI:
-		bus_flags = DRM_BUS_FLAG_DE_LOW |
-			    DRM_BUS_FLAG_DE_HIGH |
-			    DRM_BUS_FLAG_PIXDATA_SAMPLE_POSEDGE |
-			    DRM_BUS_FLAG_PIXDATA_SAMPLE_NEGEDGE |
-			    DRM_BUS_FLAG_DATA_MSB_TO_LSB |
-			    DRM_BUS_FLAG_DATA_LSB_TO_MSB |
-			    DRM_BUS_FLAG_SYNC_SAMPLE_POSEDGE |
-			    DRM_BUS_FLAG_SYNC_SAMPLE_NEGEDGE;
-		if (desc->bus_flags & ~bus_flags)
-			dev_warn(dev, "Unexpected bus_flags(%d)\n", desc->bus_flags & ~bus_flags);
-		if (!(desc->bus_flags & bus_flags))
-			dev_warn(dev, "Specify missing bus_flags\n");
-		if (desc->bus_format == 0)
-			dev_warn(dev, "Specify missing bus_format\n");
-		if (desc->bpc != 6 && desc->bpc != 8)
-			dev_warn(dev, "Expected bpc in {6,8} but got: %u\n", desc->bpc);
-		break;
-	default:
-		dev_warn(dev, "Specify a valid connector_type: %d\n", desc->connector_type);
-		connector_type = DRM_MODE_CONNECTOR_DPI;
-		break;
 	}
 
 	dev_set_drvdata(dev, panel);