[PATCH 4/7] drm/vmwgfx: Stop using plane->fb in vmw_kms_update_implicit_fb()

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

The only caller of vmw_kms_update_implicit_fb() is the page_flip
hook which itself gets called with the plane mutex already held.
Hence we can look at plane->state safely. Toss in a lockdep assert
to make the situation more clear.

Cc: Thomas Hellstrom <thellstrom at vmware.com>
Cc: Sinclair Yeh <syeh at vmware.com>
Cc: VMware Graphics <linux-graphics-maintainer at vmware.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_kms.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
index 5a824125c231..a93d290b0f35 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
@@ -2811,14 +2811,17 @@ void vmw_kms_update_implicit_fb(struct vmw_private *dev_priv,
 				struct drm_crtc *crtc)
 {
 	struct vmw_display_unit *du = vmw_crtc_to_du(crtc);
+	struct drm_plane *plane = crtc->primary;
 	struct vmw_framebuffer *vfb;
 
+	lockdep_assert_held(&plane->mutex);
+
 	mutex_lock(&dev_priv->global_kms_state_mutex);
 
 	if (!du->is_implicit)
 		goto out_unlock;
 
-	vfb = vmw_framebuffer_to_vfb(crtc->primary->fb);
+	vfb = vmw_framebuffer_to_vfb(plane->state->fb);
 	WARN_ON_ONCE(dev_priv->num_implicit != 1 &&
 		     dev_priv->implicit_fb != vfb);
 
-- 
2.16.1