drm: Move locking into drm_debugfs_crtc_crc_add

There's no reason any more for callers of this function to take the lock
themselves, so just move the lock to the function to avoid confusion and
bugs when more callers are contributed.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Robert Foss <robert.foss@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170102125912.22305-2-tomeu.vizoso@collabora.com

drivers/gpu/drm/drm_debugfs_crc.c

@@ -325,16 +325,19 @@ int drm_crtc_add_crc_entry(struct drm_crtc *crtc, bool has_frame,
 	struct drm_crtc_crc_entry *entry;
 	int head, tail;
 
-	assert_spin_locked(&crc->lock);
+	spin_lock(&crc->lock);
 
 	/* Caller may not have noticed yet that userspace has stopped reading */
-	if (!crc->opened)
+	if (!crc->opened) {
+		spin_unlock(&crc->lock);
 		return -EINVAL;
+	}
 
 	head = crc->head;
 	tail = crc->tail;
 
 	if (CIRC_SPACE(head, tail, DRM_CRC_ENTRIES_NR) < 1) {
+		spin_unlock(&crc->lock);
 		DRM_ERROR("Overflow of CRC buffer, userspace reads too slow.\n");
 		return -ENOBUFS;
 	}
@@ -347,6 +350,8 @@ int drm_crtc_add_crc_entry(struct drm_crtc *crtc, bool has_frame,
 	head = (head + 1) & (DRM_CRC_ENTRIES_NR - 1);
 	crc->head = head;
 
+	spin_unlock(&crc->lock);
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(drm_crtc_add_crc_entry);