drm/omap: populate DSI platform bus earlier

After the changes from 4.20 the DSI encoder tries to find the
attached panel before populating the DSI bus. If the panel is
not found -EPROBE_DEFER is returned, so the DSI bus is never
populated and the panel never added.

Fix this by populating the DSI bus before searching for the
video sink in dsi_init_output().

Fixes: 27d6245 ("drm/omap: dss: Acquire next dssdev at probe time")
Acked-by: Pavel Machek <pavel@ucw.cz>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181121160916.22017-3-sebastian.reichel@collabora.com

drivers/gpu/drm/omapdrm/dss/dsi.c

@@ -5418,32 +5418,32 @@ static int dsi_probe(struct platform_device *pdev)
 		dsi->num_lanes_supported = 3;
 	}
 
+	r = of_platform_populate(dev->of_node, NULL, NULL, dev);
+	if (r) {
+		DSSERR("Failed to populate DSI child devices: %d\n", r);
+		goto err_pm_disable;
+	}
+
 	r = dsi_init_output(dsi);
 	if (r)
-		goto err_pm_disable;
+		goto err_of_depopulate;
 
 	r = dsi_probe_of(dsi);
 	if (r) {
 		DSSERR("Invalid DSI DT data\n");
 		goto err_uninit_output;
 	}
 
-	r = of_platform_populate(dev->of_node, NULL, NULL, dev);
-	if (r) {
-		DSSERR("Failed to populate DSI child devices: %d\n", r);
-		goto err_uninit_output;
-	}
-
 	r = component_add(&pdev->dev, &dsi_component_ops);
 	if (r)
-		goto err_of_depopulate;
+		goto err_uninit_output;
 
 	return 0;
 
-err_of_depopulate:
-	of_platform_depopulate(dev);
 err_uninit_output:
 	dsi_uninit_output(dsi);
+err_of_depopulate:
+	of_platform_depopulate(dev);
 err_pm_disable:
 	pm_runtime_disable(dev);
 	return r;