drm: apple: iomfb: Extend hotplug/mode parsing logging

Under unknown but slightly broken conditions dcp sends timing modes
without linked color modes. Log a warning when this happens and log the
number of valid modes before emitting HPD events.

Signed-off-by: Janne Grunau <j@jannau.net>

Author: jannau

drivers/gpu/drm/apple/iomfb.c

@@ -238,8 +238,8 @@ void dcp_hotplug(struct work_struct *work)
 	connector = container_of(work, struct apple_connector, hotplug_wq);
 
 	dcp = platform_get_drvdata(connector->dcp);
-	dev_info(dcp->dev, "%s() connected:%d valid_mode:%d\n", __func__,
-		 connector->connected, dcp->valid_mode);
+	dev_info(dcp->dev, "%s() connected:%d valid_mode:%d nr_modes:%u\n", __func__,
+		 connector->connected, dcp->valid_mode, dcp->nr_modes);
 
 	/*
 	 * DCP defers link training until we set a display mode. But we set

drivers/gpu/drm/apple/iomfb_template.c

@@ -567,6 +567,8 @@ static bool dcpep_process_chunks(struct apple_dcp *dcp,
 			dcp->nr_modes = 0;
 			return false;
 		}
+		if (dcp->nr_modes == 0)
+			dev_warn(dcp->dev, "TimingElements without valid modes!\n");
 	} else if (!strcmp(req->key, "DisplayAttributes")) {
 		/* DisplayAttributes are empty for integrated displays, use
 		 * display dimensions read from the devicetree