In cases where old_state may not be present we hit a null dereference.
Get display unit from cursor plane instead to fix this and also do an
early return if there is no new_state since there is nothing to do in
that case.
This fixes igt test kms_cursor_legacy@torture-bo.

Fixes: 965544150d1c ("drm/vmwgfx: Refactor cursor handling")
Cc: Zack Rusin <[email protected]>
Cc: Broadcom internal kernel review list <[email protected]>
Cc: [email protected]
Signed-off-by: Maaz Mombasawala <[email protected]>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_cursor_plane.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_cursor_plane.c 
b/drivers/gpu/drm/vmwgfx/vmwgfx_cursor_plane.c
index b010fc7ca68e..35e3fd2bbdad 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_cursor_plane.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_cursor_plane.c
@@ -22,6 +22,9 @@
 #define VMW_CURSOR_SNOOP_WIDTH 64
 #define VMW_CURSOR_SNOOP_HEIGHT 64
 
+#define vmw_cursor_to_du(cursor_plane) \
+       container_of(cursor_plane, struct vmw_display_unit, cursor.base)
+
 struct vmw_svga_fifo_cmd_define_cursor {
        u32 cmd;
        SVGAFifoCmdDefineAlphaCursor cursor;
@@ -742,13 +745,14 @@ vmw_cursor_plane_atomic_update(struct drm_plane *plane,
                               struct drm_atomic_commit *state)
 {
        struct vmw_bo *bo;
-       struct drm_plane_state *new_state =
-               drm_atomic_get_new_plane_state(state, plane);
-       struct drm_plane_state *old_state =
-               drm_atomic_get_old_plane_state(state, plane);
-       struct drm_crtc *crtc = new_state->crtc ?: old_state->crtc;
+       struct drm_plane_state *new_state;
+
+       new_state = drm_atomic_get_new_plane_state(state, plane);
+       if (!new_state)
+               return;
+
        struct vmw_private *dev_priv = vmw_priv(plane->dev);
-       struct vmw_display_unit *du = vmw_crtc_to_du(crtc);
+       struct vmw_display_unit *du = vmw_cursor_to_du(plane);
        struct vmw_plane_state *vps = vmw_plane_state_to_vps(new_state);
        s32 hotspot_x, hotspot_y, cursor_x, cursor_y;
 
-- 
2.54.0

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