linux-kernel - [PATCH 1/3] drm/exynos: plane: Disable fully off-screen planes instead of zero-sized update

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Message-ID: <20250929043110.3631025-2-hy_fifty.lee@samsung.com>
Date: Mon, 29 Sep 2025 13:31:08 +0900
From: Hoyoung Lee <hy_fifty.lee@...sung.com>
To: Inki Dae <inki.dae@...sung.com>, Seung-Woo Kim <sw0312.kim@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>, David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>, Krzysztof Kozlowski <krzk@...nel.org>, Alim
	Akhtar <alim.akhtar@...sung.com>
Cc: Hoyoung Lee <hy_fifty.lee@...sung.com>, dri-devel@...ts.freedesktop.org,
	linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] drm/exynos: plane: Disable fully off-screen planes
 instead of zero-sized update

Some configurations require additional actions when all windows are
disabled to keep DECON operating correctly. Programming a zero-sized window
in ->atomic_update() leaves the plane logically enabled and can bypass
those disable semantics.

Treat a fully off-screen plane as not visible and take the explicit disable
path.

Implementation details:
- exynos_plane_mode_set(): if computed actual_w/actual_h is zero, mark
  state->visible = false and return early.
- exynos_plane_atomic_check(): if !visible, skip further checks and
  return 0.
- exynos_plane_atomic_update(): if !visible, call ->disable_plane();
  otherwise call ->update_plane().

No functional change for visible planes; off-screen planes are now cleanly
disabled, ensuring the disable hooks run consistently.

Signed-off-by: Hoyoung Lee <hy_fifty.lee@...sung.com>
---
 drivers/gpu/drm/exynos/exynos_drm_plane.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_plane.c b/drivers/gpu/drm/exynos/exynos_drm_plane.c
index 7c3aa77186d3..842974154d79 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_plane.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_plane.c
@@ -91,6 +91,11 @@ static void exynos_plane_mode_set(struct exynos_drm_plane_state *exynos_state)
 	actual_w = exynos_plane_get_size(crtc_x, crtc_w, mode->hdisplay);
 	actual_h = exynos_plane_get_size(crtc_y, crtc_h, mode->vdisplay);
 
+	if (!actual_w || !actual_h) {
+		state->visible = false;
+		return;
+	}
+
 	if (crtc_x < 0) {
 		if (actual_w)
 			src_x += ((-crtc_x) * exynos_state->h_ratio) >> 16;
@@ -244,6 +249,9 @@ static int exynos_plane_atomic_check(struct drm_plane *plane,
 	/* translate state into exynos_state */
 	exynos_plane_mode_set(exynos_state);
 
+	if (!new_plane_state->visible)
+		return 0;
+
 	ret = exynos_drm_plane_check_format(exynos_plane->config, exynos_state);
 	if (ret)
 		return ret;
@@ -263,8 +271,10 @@ static void exynos_plane_atomic_update(struct drm_plane *plane,
 	if (!new_state->crtc)
 		return;
 
-	if (exynos_crtc->ops->update_plane)
+	if (new_state->visible && exynos_crtc->ops->update_plane)
 		exynos_crtc->ops->update_plane(exynos_crtc, exynos_plane);
+	else if (exynos_crtc->ops->disable_plane)
+		exynos_crtc->ops->disable_plane(exynos_crtc, exynos_plane);
 }
 
 static void exynos_plane_atomic_disable(struct drm_plane *plane,
-- 
2.34.1