drm: Fix deadlock due to getconnector locking changes

In commit ccfc08655d5fd5076828f45fb09194c070f2f63a
Author: Rob Clark <[e-mail]>
Date: Thu Dec 18 16:01:48 2014 -0500

drm: tweak getconnector locking

We need to extend the locking to cover connector->state reading for
atomic drivers, but the above commit was a bit too eager and also
included the fill_modes callback. Which on i915 on old platforms using
load detection needs to acquire modeset locks, resulting in a deadlock
on output probing.

Reported-by: Marc Finet <[e-mail]>
Cc: Marc Finet <[e-mail]>
Cc: [e-mail]
Signed-off-by: Daniel Vetter <[e-mail]>
Reviewed-by: Rob Clark <[e-mail]>
Signed-off-by: Dave Airlie <[e-mail]>

drivers/gpu/drm/drm_crtc.c

···
 	DRM_DEBUG_KMS("[CONNECTOR:%d:?]\n", out_resp->connector_id);
 
 	mutex_lock(&dev->mode_config.mutex);
-	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
 
 	connector = drm_connector_find(dev, out_resp->connector_id);
 	if (!connector) {
···
 	out_resp->mm_height = connector->display_info.height_mm;
 	out_resp->subpixel = connector->display_info.subpixel_order;
 	out_resp->connection = connector->status;
+
+	drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
 	encoder = drm_connector_get_encoder(connector);
 	if (encoder)
 		out_resp->encoder_id = encoder->base.id;