From: Andy Yan <andy....@rock-chips.com>

The alpha setup should start from the second layer, the current calculation
starts incorrectly from the first layer, a negative offset will be obtained
in the following formula:

offset = (mixer_id + zpos - 1) * 0x10

Fixes: 604be85547ce ("drm/rockchip: Add VOP2 driver")
Tested-by: Derek Foreman <derek.fore...@collabora.com>
Signed-off-by: Andy Yan <andy....@rock-chips.com>
---

(no changes since v1)

 drivers/gpu/drm/rockchip/rockchip_drm_vop2.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c 
b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
index d0b2b881ff07..1f0fa153c62e 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop2.c
@@ -2459,6 +2459,12 @@ static void vop2_setup_alpha(struct vop2_video_port *vp)
                struct vop2_win *win = to_vop2_win(plane);
                int zpos = plane->state->normalized_zpos;
 
+               /*
+                * Need to configure alpha from second layer.
+                */
+               if (zpos == 0)
+                       continue;
+
                if (plane->state->pixel_blend_mode == DRM_MODE_BLEND_PREMULTI)
                        premulti_en = 1;
                else
-- 
2.34.1

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