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* [PATCH] [RFC]: drm/i915/display: Use ceiling division for NV12 UV surface offset calculation
@ 2026-04-11 17:15 Vidya Srinivas
  2026-04-11 17:27 ` ✓ CI.KUnit: success for : " Patchwork
                   ` (12 more replies)
  0 siblings, 13 replies; 22+ messages in thread
From: Vidya Srinivas @ 2026-04-11 17:15 UTC (permalink / raw)
  To: intel-gfx; +Cc: intel-xe, Vidya Srinivas

For LNL+, odd source size and panning for YUV 422/420 surfaces is
supported. However, it requires the UV (chroma) surface Start X/Y and
width/height to be calculated as ceiling(half of Y plane value) rather
than floor. The current code uses (>> 17) which is floor division. For
odd Y plane values this produces an off-by-one error in the UV plane
offset.

On Android systems we see PLANE ATS fault when NV12 overlays are
used with odd source dimensions:

[  126.854200] xe 0000:00:02.0: [drm:intel_atomic_setup_scaler [xe]] [CRTC:148:pipe A] attached scaler id 0.0 to PLANE:33
[  126.854617] xe 0000:00:02.0: [drm:skl_update_scaler [xe]] [CRTC:148:pipe A] scaler_user index 0.0: staged scaling request for 1279x719->1340x753
[  126.854837] xe 0000:00:02.0: [drm:intel_plane_atomic_check [xe]] UV plane [PLANE:33:plane 1A] using Y plane [PLANE:123:plane 4A]
[  126.854926] xe 0000:00:02.0: [drm] *ERROR* [CRTC:148:pipe A] PLANE ATS fault

With Y plane width 1279:
  floor(1279/2) = 639 (current)
  ceil(1279/2)  = 640 (required)

Change the UV offset/size calculation to use ceiling division by adding
(1 << 17) - 1 before shifting. This is a no-op for even values since
ceiling and floor are equal when the dividend is even.

Signed-off-by: Vidya Srinivas <vidya.srinivas@intel.com>
---
 drivers/gpu/drm/i915/display/skl_universal_plane.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/skl_universal_plane.c b/drivers/gpu/drm/i915/display/skl_universal_plane.c
index 7a9d494334b5..c455bf92ae99 100644
--- a/drivers/gpu/drm/i915/display/skl_universal_plane.c
+++ b/drivers/gpu/drm/i915/display/skl_universal_plane.c
@@ -2139,10 +2139,16 @@ static int skl_check_nv12_aux_surface(struct intel_plane_state *plane_state)
 	int min_height = intel_plane_min_height(plane, fb, uv_plane, rotation);
 	int max_width = intel_plane_max_width(plane, fb, uv_plane, rotation);
 	int max_height = intel_plane_max_height(plane, fb, uv_plane, rotation);
-	int x = plane_state->uapi.src.x1 >> 17;
-	int y = plane_state->uapi.src.y1 >> 17;
-	int w = drm_rect_width(&plane_state->uapi.src) >> 17;
-	int h = drm_rect_height(&plane_state->uapi.src) >> 17;
+
+	/*
+	 * LNL+ UV surface start/size =
+	 * ceiling(half of Y plane start/size). Use ceiling division
+	 * unconditionally; it is a no-op for even values.
+	 */
+	int x = (plane_state->uapi.src.x1 + (1 << 17) - 1) >> 17;
+	int y = (plane_state->uapi.src.y1 + (1 << 17) - 1) >> 17;
+	int w = (drm_rect_width(&plane_state->uapi.src) + (1 << 17) - 1) >> 17;
+	int h = (drm_rect_height(&plane_state->uapi.src) + (1 << 17) - 1) >> 17;
 	u32 offset;
 
 	/* FIXME not quite sure how/if these apply to the chroma plane */
-- 
2.45.2


^ permalink raw reply related	[flat|nested] 22+ messages in thread
end of thread, other threads:[~2026-04-29 11:08 UTC | newest]

Thread overview: 22+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-04-11 17:15 [PATCH] [RFC]: drm/i915/display: Use ceiling division for NV12 UV surface offset calculation Vidya Srinivas
2026-04-11 17:27 ` ✓ CI.KUnit: success for : " Patchwork
2026-04-11 18:14 ` ✓ Xe.CI.BAT: " Patchwork
2026-04-11 19:03 ` ✗ Xe.CI.FULL: failure " Patchwork
2026-04-14 15:42 ` [PATCH] [RFC]: " Jani Nikula
2026-04-14 17:10   ` Srinivas, Vidya
2026-04-14 17:59     ` Shankar, Uma
2026-04-15  0:23       ` Srinivas, Vidya
2026-04-15  0:15 ` Vidya Srinivas
2026-04-15 11:59   ` Jani Nikula
2026-04-15 17:06     ` Srinivas, Vidya
2026-04-17  2:03       ` Srinivas, Vidya
2026-04-15  1:10 ` ✓ CI.KUnit: success for : drm/i915/display: Use ceiling division for NV12 UV surface offset calculation (rev2) Patchwork
2026-04-15  2:10 ` ✓ Xe.CI.BAT: " Patchwork
2026-04-15  3:01 ` ✗ Xe.CI.FULL: failure " Patchwork
2026-04-15 16:58 ` [PATCH] [RFC v3]: drm/i915/display: Use ceiling division for NV12 UV surface offset calculation Vidya Srinivas
2026-04-29 11:07   ` Juha-Pekka Heikkilä
2026-04-29 11:08     ` Srinivas, Vidya
2026-04-15 17:09 ` ✗ CI.checkpatch: warning for : drm/i915/display: Use ceiling division for NV12 UV surface offset calculation (rev3) Patchwork
2026-04-15 17:11 ` ✓ CI.KUnit: success " Patchwork
2026-04-15 18:08 ` ✓ Xe.CI.BAT: " Patchwork
2026-04-15 20:00 ` ✗ Xe.CI.FULL: failure " Patchwork

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