[PATCH v2] drm/stm: ltdc: attach immutable zpos property to planes

[Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>]

Defines plane ordering by hard-coding an immutable Z position from the
first plane, used as primary layer, to the next ones as overlay in order
of instantiation.

This zpos is only an information as it is not possible to modify it,
blending operations are still applied from the top to the bottom layer.

This patch helps to remove a warning message from the Android
Hardware Composer.

Signed-off-by: Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>
Acked-by: Yannick Fertre <yannick.fertre@foss.st.com>
Reviewed-by: Yannick Fertre <yannick.fertre@foss.st.com>
---
 drivers/gpu/drm/stm/ltdc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
index 195de30eb90c..bd603ef5e935 100644
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -1024,6 +1024,8 @@ static int ltdc_crtc_init(struct drm_device *ddev, struct drm_crtc *crtc)
 		return -EINVAL;
 	}
 
+	drm_plane_create_zpos_immutable_property(primary, 0);
+
 	ret = drm_crtc_init_with_planes(ddev, crtc, primary, NULL,
 					&ltdc_crtc_funcs, NULL);
 	if (ret) {
@@ -1046,6 +1048,7 @@ static int ltdc_crtc_init(struct drm_device *ddev, struct drm_crtc *crtc)
 			DRM_ERROR("Can not create overlay plane %d\n", i);
 			goto cleanup;
 		}
+		drm_plane_create_zpos_immutable_property(overlay, i);
 	}
 
 	return 0;
-- 
2.17.1