drm/gma500: Drop dev->struct_mutex from modeset code

It's either init code or already protected by other means. Note
that psb_gtt_pin/unpin has it's own lock, and that's really the
only piece of driver private state - all the modeset state is
protected with modeset locks already.

The only important bit is to switch all gem_obj_unref calls to the
_unlocked variant.

Cc: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Acked-by: Patrik Jakobsson <patrik.r.jakobsson@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1448271183-20523-18-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/gma500/gma_display.c

@@ -349,8 +349,6 @@ int gma_crtc_cursor_set(struct drm_crtc *crtc,
 	/* If we didn't get a handle then turn the cursor off */
 	if (!handle) {
 		temp = CURSOR_MODE_DISABLE;
-		mutex_lock(&dev->struct_mutex);
-
 		if (gma_power_begin(dev, false)) {
 			REG_WRITE(control, temp);
 			REG_WRITE(base, 0);
@@ -362,11 +360,9 @@ int gma_crtc_cursor_set(struct drm_crtc *crtc,
 			gt = container_of(gma_crtc->cursor_obj,
 					  struct gtt_range, gem);
 			psb_gtt_unpin(gt);
-			drm_gem_object_unreference(gma_crtc->cursor_obj);
+			drm_gem_object_unreference_unlocked(gma_crtc->cursor_obj);
 			gma_crtc->cursor_obj = NULL;
 		}
-
-		mutex_unlock(&dev->struct_mutex);
 		return 0;
 	}
 
@@ -376,7 +372,6 @@ int gma_crtc_cursor_set(struct drm_crtc *crtc,
 		return -EINVAL;
 	}
 
-	mutex_lock(&dev->struct_mutex);
 	obj = drm_gem_object_lookup(dev, file_priv, handle);
 	if (!obj) {
 		ret = -ENOENT;
@@ -441,17 +436,15 @@ int gma_crtc_cursor_set(struct drm_crtc *crtc,
 	if (gma_crtc->cursor_obj) {
 		gt = container_of(gma_crtc->cursor_obj, struct gtt_range, gem);
 		psb_gtt_unpin(gt);
-		drm_gem_object_unreference(gma_crtc->cursor_obj);
+		drm_gem_object_unreference_unlocked(gma_crtc->cursor_obj);
 	}
 
 	gma_crtc->cursor_obj = obj;
 unlock:
-	mutex_unlock(&dev->struct_mutex);
 	return ret;
 
 unref_cursor:
-	drm_gem_object_unreference(obj);
-	mutex_unlock(&dev->struct_mutex);
+	drm_gem_object_unreference_unlocked(obj);
 	return ret;
 }