drm/vmwgfx: Kill some lockdep warnings

Some global KMS state that is elsewhere protected by the mode_config
mutex here needs to be protected with a local mutex. Remove corresponding
lockdep checks and introduce a new driver-private global_kms_state_mutex,
and make sure its locking order is *after* the crtc locks in order to
avoid having to release those when the new mutex is taken.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Cc: <stable@vger.kernel.org> # 4.6

drivers/gpu/drm/vmwgfx/vmwgfx_drv.c

@@ -628,6 +628,7 @@ static int vmw_driver_load(struct drm_device *dev, unsigned long chipset)
 	mutex_init(&dev_priv->cmdbuf_mutex);
 	mutex_init(&dev_priv->release_mutex);
 	mutex_init(&dev_priv->binding_mutex);
+	mutex_init(&dev_priv->global_kms_state_mutex);
 	rwlock_init(&dev_priv->resource_lock);
 	ttm_lock_init(&dev_priv->reservation_sem);
 	spin_lock_init(&dev_priv->hw_lock);

drivers/gpu/drm/vmwgfx/vmwgfx_drv.h

@@ -412,6 +412,7 @@ struct vmw_private {
 	struct drm_property *implicit_placement_property;
 	unsigned num_implicit;
 	struct vmw_framebuffer *implicit_fb;
+	struct mutex global_kms_state_mutex;
 
 	/*
 	 * Context and surface management.

drivers/gpu/drm/vmwgfx/vmwgfx_kms.c

@@ -2143,13 +2143,13 @@ int vmw_kms_fbdev_init_data(struct vmw_private *dev_priv,
 void vmw_kms_del_active(struct vmw_private *dev_priv,
 			struct vmw_display_unit *du)
 {
-	lockdep_assert_held_once(&dev_priv->dev->mode_config.mutex);
-
+	mutex_lock(&dev_priv->global_kms_state_mutex);
 	if (du->active_implicit) {
 		if (--(dev_priv->num_implicit) == 0)
 			dev_priv->implicit_fb = NULL;
 		du->active_implicit = false;
 	}
+	mutex_unlock(&dev_priv->global_kms_state_mutex);
 }
 
 /**
@@ -2165,15 +2165,15 @@ void vmw_kms_add_active(struct vmw_private *dev_priv,
 			struct vmw_display_unit *du,
 			struct vmw_framebuffer *vfb)
 {
-	lockdep_assert_held_once(&dev_priv->dev->mode_config.mutex);
-
+	mutex_lock(&dev_priv->global_kms_state_mutex);
 	WARN_ON_ONCE(!dev_priv->num_implicit && dev_priv->implicit_fb);
 
 	if (!du->active_implicit && du->is_implicit) {
 		dev_priv->implicit_fb = vfb;
 		du->active_implicit = true;
 		dev_priv->num_implicit++;
 	}
+	mutex_unlock(&dev_priv->global_kms_state_mutex);
 }
 
 /**
@@ -2190,16 +2190,13 @@ bool vmw_kms_crtc_flippable(struct vmw_private *dev_priv,
 			    struct drm_crtc *crtc)
 {
 	struct vmw_display_unit *du = vmw_crtc_to_du(crtc);
+	bool ret;
 
-	lockdep_assert_held_once(&dev_priv->dev->mode_config.mutex);
-
-	if (!du->is_implicit)
-		return true;
-
-	if (dev_priv->num_implicit != 1)
-		return false;
+	mutex_lock(&dev_priv->global_kms_state_mutex);
+	ret = !du->is_implicit || dev_priv->num_implicit == 1;
+	mutex_unlock(&dev_priv->global_kms_state_mutex);
 
-	return true;
+	return ret;
 }
 
 /**
@@ -2214,16 +2211,18 @@ void vmw_kms_update_implicit_fb(struct vmw_private *dev_priv,
 	struct vmw_display_unit *du = vmw_crtc_to_du(crtc);
 	struct vmw_framebuffer *vfb;
 
-	lockdep_assert_held_once(&dev_priv->dev->mode_config.mutex);
+	mutex_lock(&dev_priv->global_kms_state_mutex);
 
 	if (!du->is_implicit)
-		return;
+		goto out_unlock;
 
 	vfb = vmw_framebuffer_to_vfb(crtc->primary->fb);
 	WARN_ON_ONCE(dev_priv->num_implicit != 1 &&
 		     dev_priv->implicit_fb != vfb);
 
 	dev_priv->implicit_fb = vfb;
+out_unlock:
+	mutex_unlock(&dev_priv->global_kms_state_mutex);
 }
 
 /**

drivers/gpu/drm/vmwgfx/vmwgfx_scrn.c

@@ -285,14 +285,17 @@ static int vmw_sou_crtc_set_config(struct drm_mode_set *set)
 	}
 
 	/* Only one active implicit frame-buffer at a time. */
+	mutex_lock(&dev_priv->global_kms_state_mutex);
 	if (sou->base.is_implicit &&
 	    dev_priv->implicit_fb && vfb &&
 	    !(dev_priv->num_implicit == 1 &&
 	      sou->base.active_implicit) &&
 	    dev_priv->implicit_fb != vfb) {
+		mutex_unlock(&dev_priv->global_kms_state_mutex);
 		DRM_ERROR("Multiple implicit framebuffers not supported.\n");
 		return -EINVAL;
 	}
+	mutex_unlock(&dev_priv->global_kms_state_mutex);
 
 	/* since they always map one to one these are safe */
 	connector = &sou->base.connector;

drivers/gpu/drm/vmwgfx/vmwgfx_stdu.c

@@ -553,12 +553,15 @@ static int vmw_stdu_crtc_set_config(struct drm_mode_set *set)
 	}
 
 	/* Only one active implicit frame-buffer at a time. */
+	mutex_lock(&dev_priv->global_kms_state_mutex);
 	if (!turning_off && stdu->base.is_implicit && dev_priv->implicit_fb &&
 	    !(dev_priv->num_implicit == 1 && stdu->base.active_implicit)
 	    && dev_priv->implicit_fb != vfb) {
+		mutex_unlock(&dev_priv->global_kms_state_mutex);
 		DRM_ERROR("Multiple implicit framebuffers not supported.\n");
 		return -EINVAL;
 	}
+	mutex_unlock(&dev_priv->global_kms_state_mutex);
 
 	/* Since they always map one to one these are safe */
 	connector = &stdu->base.connector;