drm/radeon: Sprinkle drm_modeset_lock_all to appease locking checks

In

commit 7a3f3d6667f5f9ffd1517f6b21d64bbf5312042c
Author: Daniel Vetter <[e-mail]>
Date: Thu Jul 9 23:44:28 2015 +0200

drm: Check locking in drm_for_each_connector

I added locking checks to drm_for_each_connector but failed that
through drm_helper_connector_dpms -> drm_helper_choose_encoder_dpms
it's used in a few more places in the radeon resume/suspend code.

Fix them up.

Note that we could use the connector iterator macros in there too, but
that's for the future.

Reported-and-tested-by: Borislav Petkov <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Alex Deucher <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/radeon/radeon_device.c

···
 
 	drm_kms_helper_poll_disable(dev);
 
+	drm_modeset_lock_all(dev);
 	/* turn off display hw */
 	list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
 		drm_helper_connector_dpms(connector, DRM_MODE_DPMS_OFF);
 	}
+	drm_modeset_unlock_all(dev);
 
 	/* unpin the front buffers and cursors */
 	list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
···
 	if (fbcon) {
 		drm_helper_resume_force_mode(dev);
 		/* turn on display hw */
+		drm_modeset_lock_all(dev);
 		list_for_each_entry(connector, &dev->mode_config.connector_list, head) {
 			drm_helper_connector_dpms(connector, DRM_MODE_DPMS_ON);
 		}
+		drm_modeset_unlock_all(dev);
 	}
 
 	drm_kms_helper_poll_enable(dev);