linux-kernel - [PATCH] drm/atmel-hlcdc: don't reject the commit if the src rect has fractional parts

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Message-ID: <20251120-lcd_scaling_fix-v1-1-5ffc98557923@microchip.com>
Date: Thu, 20 Nov 2025 11:38:25 +0100
From: Ludovic Desroches <ludovic.desroches@...rochip.com>
To: Manikandan Muralidharan <manikandan.m@...rochip.com>, "Dharma
 Balasubiramani" <dharma.b@...rochip.com>, Maarten Lankhorst
	<maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>, Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>, Claudiu Beznea
	<claudiu.beznea@...on.dev>
CC: <dri-devel@...ts.freedesktop.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, Ludovic Desroches
	<ludovic.desroches@...rochip.com>
Subject: [PATCH] drm/atmel-hlcdc: don't reject the commit if the src rect
 has fractional parts

Don’t reject the commit when the source rectangle has fractional parts.
This can occur due to scaling: drm_atomic_helper_check_plane_state() calls
drm_rect_clip_scaled(), which may introduce fractional parts while
computing the clipped source rectangle. This does not imply the commit is
invalid, so we should accept it instead of discarding it.

Signed-off-by: Ludovic Desroches <ludovic.desroches@...rochip.com>
---
 drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c | 19 ++++---------------
 1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c
index 92132be9823f1e705d266f9547702ea9530bd043..bccfe055c087e5632d60503e8e4bcb3d9e18ce50 100644
--- a/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c
+++ b/drivers/gpu/drm/atmel-hlcdc/atmel_hlcdc_plane.c
@@ -79,8 +79,6 @@ drm_plane_state_to_atmel_hlcdc_plane_state(struct drm_plane_state *s)
 	return container_of(s, struct atmel_hlcdc_plane_state, base);
 }
 
-#define SUBPIXEL_MASK			0xffff
-
 static uint32_t rgb_formats[] = {
 	DRM_FORMAT_C8,
 	DRM_FORMAT_XRGB4444,
@@ -745,24 +743,15 @@ static int atmel_hlcdc_plane_atomic_check(struct drm_plane *p,
 	if (ret || !s->visible)
 		return ret;
 
-	hstate->src_x = s->src.x1;
-	hstate->src_y = s->src.y1;
-	hstate->src_w = drm_rect_width(&s->src);
-	hstate->src_h = drm_rect_height(&s->src);
+	hstate->src_x = s->src.x1 >> 16;
+	hstate->src_y = s->src.y1 >> 16;
+	hstate->src_w = drm_rect_width(&s->src) >> 16;
+	hstate->src_h = drm_rect_height(&s->src) >> 16;
 	hstate->crtc_x = s->dst.x1;
 	hstate->crtc_y = s->dst.y1;
 	hstate->crtc_w = drm_rect_width(&s->dst);
 	hstate->crtc_h = drm_rect_height(&s->dst);
 
-	if ((hstate->src_x | hstate->src_y | hstate->src_w | hstate->src_h) &
-	    SUBPIXEL_MASK)
-		return -EINVAL;
-
-	hstate->src_x >>= 16;
-	hstate->src_y >>= 16;
-	hstate->src_w >>= 16;
-	hstate->src_h >>= 16;
-
 	hstate->nplanes = fb->format->num_planes;
 	if (hstate->nplanes > ATMEL_HLCDC_LAYER_MAX_PLANES)
 		return -EINVAL;

---
base-commit: fe4d0dea039f2befb93f27569593ec209843b0f5
change-id: 20251119-lcd_scaling_fix-a4842d86307c

Best regards,
-- 
Ludovic Desroches <ludovic.desroches@...rochip.com>