[PATCH AUTOSEL 6.6 106/139] drm/stm: ltdc: reset plane transparency after plane disable

[Sasha Levin]

From: Yannick Fertre <yannick.fertre at foss.st.com>

[ Upstream commit 02fa62d41c8abff945bae5bfc3ddcf4721496aca ]

The plane's opacity should be reseted while the plane
is disabled. It prevents from seeing a possible global
or layer background color set earlier.

Signed-off-by: Yannick Fertre <yannick.fertre at foss.st.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240712131344.98113-1-yannick.fertre@foss.st.com
Signed-off-by: Raphael Gallais-Pou <raphael.gallais-pou at foss.st.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 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 eeaabb4e10d3e..9e76785cb2691 100644
--- a/drivers/gpu/drm/stm/ltdc.c
+++ b/drivers/gpu/drm/stm/ltdc.c
@@ -1513,6 +1513,9 @@ static void ltdc_plane_atomic_disable(struct drm_plane *plane,
 	/* Disable layer */
 	regmap_write_bits(ldev->regmap, LTDC_L1CR + lofs, LXCR_LEN | LXCR_CLUTEN |  LXCR_HMEN, 0);
 
+	/* Reset the layer transparency to hide any related background color */
+	regmap_write_bits(ldev->regmap, LTDC_L1CACR + lofs, LXCACR_CONSTA, 0x00);
+
 	/* Commit shadow registers = update plane at next vblank */
 	if (ldev->caps.plane_reg_shadow)
 		regmap_write_bits(ldev->regmap, LTDC_L1RCR + lofs,
-- 
2.43.0